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Little Transformers: Bolitotherus cornutus – the first dinobeetle?

Little Transformers are back with another coleopteran representative. I usually use this platform to present insect adaptations from the tropics, however this time I am focusing on a local species with a wide distribution in central and eastern North America: the forked fungus beetle (Bolitotherus cornutus). It is one of the most iconic North American beetle species, and I remember that flipping through pages of insect books as a kid, there was always an image of a forked fungus beetle under the darkling beetles section. In fact, as soon as I arrived to Canada this was the first species I sought after. And as much as I hate to admit, I looked for it in all the wrong places. I thought it was associated with wood (it is, but in a more indirect way), and cracked open fallen logs in search for adults. Of course I found nothing. Eventually the first fungus beetles I found were under a huge woody bracket mushroom in a conservation area near Price Edward, Ontario. Today this makes me laugh because back then we drove so far, and a year later I found out that I can find the beetles within just a mere 5 mins bus ride from my house.

I must say I am puzzled why this beetle is shown as an example for darkling beetles in books. Family Tenebrionidae is big and diverse, but there are some common characteristics that stay uniform across different genera. Bolitotherus cornutus, however, is not exactly a “typical” darkling beetle. And even though this beetle is widespread and common, it is often hard to find. When I presented this beetle in a talk to a group of local naturalists and asked how many people have seen it in the wild, only one hand was raised, surprisingly or not it came from a mushroom expert.

A pair of forked fungus beetles (Bolitotherus cornutus), dorsal view

A pair of forked fungus beetles (Bolitotherus cornutus), dorsal view

At first glance, forked fungus beetles look like they were designed by a drunk military engineer. Like most members of tribe Bolitophagini, they are built like small tanks, and to some extent they also look like ones. A compact and rugged body, sealed to the outside thanks to the tight elytra forming a protective shell. The body surface is heavily granulated to provide further shock protection in case of falling to the ground, as well as camouflage against tree bark and dried bracket mushrooms that the beetles feed on. Male beetles have two sets of horns, each with a different function.

Male forked fungus beetle (Bolitotherus cornutus)

Male forked fungus beetle (Bolitotherus cornutus)

The curved thoracic horns are hairy and used for pushing an opponent off the surface while fighting for territory and mates. The length of these horns is variable depending on various conditions (both genetic and environmental), with two extreme male morphs: major with long arching horns, and minor with short stout horns.

Male forked fungus beetle (Bolitotherus cornutus), frontal view. The thoracic horns can be long!

Male forked fungus beetle (Bolitotherus cornutus), frontal view. The thoracic horns can be long!

The other set of horns are found on the beetle’s head. These are called cephalic horns and they are sometimes missing. Their function is very peculiar: males use them as a pitchfork to scrape, lift, and throw off minor individuals that cling tightly to females. By the way, other members of Bolitophagini have horns as well, for example genus Byrsax has impressive horns that make it look like a perfect samurai helmet!

Another frontal view of a male forked fungus beetle (Bolitotherus cornutus), showing its orange pom-poms.

Another frontal view of a male forked fungus beetle (Bolitotherus cornutus), showing its orange pom-poms.

Ok, but what does Bolitotherus cornutus have to do with Little Transformers? Sure, touch the beetle and it folds its legs tightly close to its body, creating an impenetrable structure. We have seen similar defense behavior in other beetle transformers, like the Ceratocanthinae pill scarab and the shiny leaf beetle. In addition, the fungus beetles also secrete a smelly mixture of chemicals when disturbed. But the reason I am mentioning it here as a transformer is because of its horns. You see, many phylogenetically distant species share similar morphological adaptations. Studying these cases of convergent evolution can teach us something about the processes these adaptations go through, as well as their function. To be more specific, how is this…

Portrait of a male forked fungus beetle (Bolitotherus cornutus)

Portrait of a male forked fungus beetle (Bolitotherus cornutus)

…any different from this?

Portrait of Machairoceratops cronusi. Art by Andrey Atuchin, used with permission.

Portrait of Machairoceratops cronusi. Art by Andrey Atuchin, used with permission.

This fabulous artwork by Andrey Atuchin shows Machairoceratops cronusi, a recently described member of the rhino-like dinosaurs, and a relative of the famous triceratops. Yes, Bolitotherus cornutus is basically a miniature six-legged dinosaur in disguise. Now I know what you are thinking. The beetle’s horns are hairy, and the dinosaur’s aren’t. That is probably true. The Machairoceratops dinosaur might have had hairy horns. We don’t know for sure (ask yourself why). But regardless, you have to agree that there is some uncanny resemblance between the two animals’ head structure. A set of flat horns arching over the head, another pair of spiky horns pointing upwards from the head, a granular neck shield… Of course, we don’t know how the dinosaurs used their horns, but we can speculate. Maybe observing the forked fungus beetles fighting can help us understand a behavior in an animal that no longer exists. The relationship between form and function in animal horns is a fascinating topic for discussion and hopefully I will write about it in more depth in the future. But I cannot help it, the more illustrations of Machairoceratops cronusi I look at, the more I see forked fungus beetles in them. It is almost as if someone placed an enormous beetle on top of the dinosaur’s skull.

Bracket mushrooms (Fomitopsis betulina) growing on birch. Bolitotherus cornutus beetles prefer to feed on old mushrooms (dark-colored, coated with moss and algae in the photo) rather than fresh ones.

Bracket mushrooms (Fomitopsis betulina) growing on birch. Bolitotherus cornutus beetles prefer to feed on old mushrooms (dark-colored, coated with moss and algae in the photo) rather than fresh ones.

The diet of forked fungus beetles is unique and restricted to bracket mushrooms (such as Fomitopsis, Ganoderma, Ischnoderma) growing on weak standing trees as well as fallen logs (by the way, they are not the only darkling beetles feeding on mushrooms). They prefer old, hardened bracket mushrooms.

Major male forked fungus beetles (Bolitotherus cornutus) fighting on top of a bracket mushroom. Notice that their granular body surface often attracts mites and tiny springtails.

Major male forked fungus beetles (Bolitotherus cornutus) fighting on top of a bracket mushroom. Notice that their granular body surface often attracts mites and tiny springtails.

On spring and summer nights males gather on the mushroom surface, where they engage in fighting tournaments to win territories (=food for the them and their offspring) and matings with the females waiting nearby. What is even more interesting is that while major males with impressive horns are distracted fighting and showing off their capabilities, the minor males sneak up on them and mate with some of the females.

A minor male forked fungus beetle (Bolitotherus cornutus) guarding a female after mating

A minor male forked fungus beetle (Bolitotherus cornutus) guarding a female after mating

The courtship process is long and elaborate, and includes climbing over the female and stridulating (acoustic communication). Males also tend to stay and guard the female to prevent other males from mating with her. After mating, females lay their eggs separately on the mushroom surface, and cover each egg with frass. This protects the eggs from desiccation as well as from predators and parasitoids.

Bolitotherus cornutus eggs appear as dark bumps on the surface of a bracket mushroom (there are 4 eggs in this photo)

Bolitotherus cornutus eggs appear as dark bumps on the surface of a bracket mushroom (there are 4 eggs in this photo)

Within 1-2 weeks the larvae hatch and immediately burrow into the mushroom. They are not the typical darkling wireworms, but instead look like hairy, soft-bodied grubs.

Young Bolitotherus cornutus larvae

Young Bolitotherus cornutus larvae

They spend their entire life inside their feeding substrate. The mushroom fruit body protects them from the elements, so they also use this space for pupation. Surprisingly, some larvae grow faster than others, and complete their metamorphosis before winter. This means that the beetles can overwinter inside the mushroom as larvae, pupae or fresh adults.

Male forked fungus beetle (Bolitotherus cornutus) emerging from a bracket mushroom

Male forked fungus beetle (Bolitotherus cornutus) emerging from a bracket mushroom

Male forked fungus beetle (Bolitotherus cornutus) burrowing into decomposing wood

Male forked fungus beetle (Bolitotherus cornutus) burrowing into decomposing wood

If you live in North America within the distribution range of this species I encourage you to get out there and look for these magnificent creatures. First of all, it is fun, and you might find other cool stuff while searching. And second, these beetles are really cool, and they can teach us a lot. They are also embarrassingly easy to keep, all they need is some pieces of the mushrooms they were collected on, the slightest humidity, and that’s it. They live for a few years as adults and readily breed in captivity, displaying all the behaviors mentioned above and more!

An active captive colony of forked fungus beetles (Bolitotherus cornutus)

An active captive colony of forked fungus beetles (Bolitotherus cornutus)

Adult forked fungus beetles (Bolitotherus cornutus) aggregating on the mushroom underside

A closeup on adult forked fungus beetles (Bolitotherus cornutus) aggregating on the mushroom underside

Little Transformers: Lamprosoma, the living Christmas ornament

Ah, the joy of transforming beetles. The first Little Transformer that opened this series of posts was a beetle – a Ceratocanthinae pill scarab that transforms into a perfect sphere and drops off to escape predators. It is an impressive evolutionary achievement that merges a successful body design and anti-predator behavior. I should mention though that many beetle species from other families use this strategy to avoid predation, some more successfully than others. One such example is a genus of small beetles from the leaf beetle family (Chrysomelidae): Lamprosoma.

Shiny leaf beetle (Lamprosoma sp.) from the Ecuadorian Amazon

Shiny leaf beetle (Lamprosoma sp.) from the Ecuadorian Amazon

When I first encountered a Lamprosoma beetle I thought it was a piece of plastic that someone discarded in the rainforest. There is something almost artificial about their appearance, shiny metallic colors combined with a compact shape. Not all species are colorful, by the way. The genus contains about 130 species, all with a neotropical distribution, some of which are completely black in color. With a body length of less than 1cm they are easy to miss in the dense vegetation of the tropical forest. Nevertheless, over the years I have encountered them more and more frequently. Unfortunately for me, identifying these beetles to the species level requires an expertise that I do not have, because there are many similar-looking species, and possibly also new species that have not been described yet.

Shiny leaf beetle (Lamprosoma sp.) from Honduras

Shiny leaf beetle (Lamprosoma sp.) from Honduras

The beetles are dome-shaped, and have very short legs. I think “cute” is the best way to describe them. As mentioned above, Lamprosoma can transform into a ball when threatened. In contrast to Ceratocanthinae beetles that have dedicated grooves to hold the legs and head in place, members of genus Lamprosoma have no such features. The beetle tucks in its head and holds its legs tightly close to its body, making it a neat impenetrable package.

Shiny leaf beetle (Lamprosoma sp.), a ventral view showing how neatly they press their legs against the body when forming the ball

Shiny leaf beetle (Lamprosoma sp.), a ventral view showing how neatly they press their legs against the body when forming the ball

Shiny leaf beetle (Lamprosoma sp.) in ball-mode. Mimicking a Christmas ornament.

Shiny leaf beetle (Lamprosoma sp.) in ball-mode. Mimicking a Christmas ornament.

In species with shiny metallic colors it is hard not to see the resemblance to the glass balls used as Christmas ornaments (maybe an idea for a future product?). Once the danger is out of sight, the beetle loosens its legs and walks away.

Shiny leaf beetle (Lamprosoma sp.) transformation sequence from ball-mode to beetle-mode. How can you not fall in love with those stubby feet?

Shiny leaf beetle (Lamprosoma sp.) transformation sequence from ball-mode to beetle-mode. How can you not fall in love with those stubby feet?

Lamprosoma are phytophagous beetles, meaning that they feed on plants. Both adults and larvae feed on leaves, and can be potential pests due to damage they can cause to foliage. The species shown here seem to be associated with cacao trees, and were found under leaves during the day. While the adults are very showy, the larvae are cryptic to avoid predators: they construct a case from frass and wood debris, and carry it around throughout their lifetime. The case is often shaped like a bent thorn, and blends perfectly with the branches the larvae live on. When threatened the larva retreat into the case and hold it firmly against the branch, preventing predators (such as ants and wasps) from accessing inside.

Another example of Lamprosoma sp. in ball-mode

Another example of Lamprosoma sp. in ball-mode

Shiny leaf beetle (Lamprosoma sp.). Full beetle-mode!

Shiny leaf beetle (Lamprosoma sp.). Full beetle-mode!

Compsus: glitter weevils with structural coloration

The insect world is full of great examples for flamboyant insects. From mosquitoes sporting feathery legs and electric blue scales, through the splash of vibrant colors in rainbow katydids, to shiny golden-green orchid bees and their mimics. But none are as dazzling as the glitter weevils of genus Compsus (family Curculionidae, subfamily Entiminae).

Short-snout weevil (Compsus sp.) from Mindo, Ecuador. It is hard to take all these colors in.

Short-snout weevil (Compsus sp.) from Mindo, Ecuador. It is hard to take all these colors in.

Compsus is a large genus distributed mainly in Central and South America, with one species occurring in North America. It contains around 140 species, mostly small to medium sized beetles of 0.5-2.5cm in length. Several species are considered as pests of citrus trees. The adult weevils feed on plant tissue: leaves, flower petals, and pollen, but they will also go for rotting leaves and fermenting fruits. The females oviposit egg masses on the aerial parts of trees. The young legless larvae hatch, drop to the ground, and burrow into the soil where they feed on the roots of the tree. At the end of its developmental stage the larva builds a chamber in the ground and pupates, and it will stay in this state for two months until the adult’s eclosion. Compsus weevils complete their life cycle within 5-7 months.

Another species of Compsus from Mindo, this one has a bit more metallic sheen to it.

Another species of Compsus from Mindo, this one has a bit more metallic sheen to it.

Compsus weevil feeding on rotting plant tissue

Compsus weevil feeding on rotting plant tissue

Freshly-eclosed short-snout weevil (Compsus sp.) use impressive mandibles to break out of the pupal skin. These scissor-like attachments drop later.

Freshly-eclosed short-snout weevil (Compsus sp.) use impressive mandibles to break out of the pupal skin. These scissor-like attachments drop later.

But what makes Compsus weevils so special, as well as other members of subfamily Entiminae, is their eye-catching colors. I would do these beetles a disservice if I didn’t explain where the colors come from, so things are about to get technical. Animal coloration is derived from spectrally selective light reflections on the outer body parts. There are two types of coloration:
1) Pigmentary (or chemical) coloration – occurs when pigments absorb scattered light in a narrow wavelength range. This type of coloration is the most common in animals.
2) Structural (or physical) coloration – achieved by nanometer-sized structures with changing refractive indices, causing coherent light scattering. Structural coloration is less common in the animal kingdom but it is widely encountered as well, and often structural colors are modified by spectrally filtering pigments.

Scales containing photonic crystals on the head of a Compsus weevil

Scales containing photonic crystals on the head of a Compsus weevil

Scales containing photonic crystals on the body surface of a Compsus weevil

Scales containing photonic crystals on the body surface of a Compsus weevil

The structures causing the physical colors are referred to as photonic crystals if they have properties (periodicity) that align with wavelengths of visible light. One-dimensional photonic crystals consist of parallel thin film layers of alternating high and low refractive index materials. These structures create the metallic and polarized reflections of cephalopods skin, the elytra of jewel beetles and scarabs, and the breast feathers of birds of paradise. Two-dimensional photonic crystals are structures with periodicity in two dimensions. An example for two-dimensional photonic crystals in animals would be the coloration of peacock feathers. Three-dimensional photonic crystals have been found in the scales of weevils and other beetles, but also in butterflies like the blue morpho.

Scales containing photonic crystals on the body surface of an Entiminae weevil (Eupholus schoenherri) from Indonesia

Scales containing photonic crystals on the body surface of an Entiminae weevil (Eupholus schoenherri) from Indonesia

Scales containing photonic crystals on the body surface of an Entiminae weevil (Eupholus schoenherri) from Indonesia

Scales containing photonic crystals on the body surface of an Entiminae weevil (Eupholus schoenherri) from Indonesia

Scales containing photonic crystals on the body surface of a Compsus weevil

Scales containing photonic crystals on the body surface of a Compsus weevil

Blue scales on the leg tarsus of an Entiminae weevil (Eupholus linnei) from Indonesia

Blue scales on the leg tarsus of an Entiminae weevil (Eupholus linnei) from Indonesia

In the case of Entiminae weevils, the adult beetles have strikingly iridescent scales, sometimes immersed in pits on the weevils’ elytra and legs. This gives the weevils a festive glittery look, as if they were covered with confetti during a big party. The reason for the bright coloration in weevils is mostly misunderstood. In some ways it may serve as camouflage in green species, but blue-colored species are very conspicuous so it remains unclear whether they advertise something to potential predators. I cannot complain: for me it is always a joy to see the cute Compsus weevils in the wild, even though sometimes it makes you feel like you missed out on a celebration or something.

 

Little Transformers: Eburia pedestris

We are back to celebrate little transformers: insects that are more than meets the eye. In this post I feature an insect whose transformation may seem a little awkward at first. It is not of cryptic nature, and it is not a case of mimicry.

While doing research about whip spiders in Belize, I also surveyed the insect biodiversity of one site, and so made sure to visit the light traps that we set up in several spots. The traps attracted an impressive diversity of insects, including moths, leafhoppers, ants, mantids, and katydids. One night a beautiful longhorn beetle (family Cerambycidae) showed up at the light trap. I did not recognize it at first so I collected it for a short Meet Your Neighbours session.

Longhorn beetle (Eburia pedestris) from Belize

Longhorn beetle (Eburia pedestris) from Belize

It was Eburia pedestris, a member in a genus of hardwood-boring longhorn beetles with a wide distribution in the Americas. I took a few decent shots. The beetle was trying to escape of course, so I reached out to grab it before it fell from the acrylic sheet. The moment I touched it something interesting happened. It crossed its legs and took a sitting position. I could not help it and I sneaked a loud laugh, because it looked like the beetle was in the middle of a yoga practice. It stayed in this comical position for a while, so I took some additional shots.

Longhorn beetle (Eburia pedestris) just sitting around

Longhorn beetle (Eburia pedestris) just sitting around

Another view of the strange pose taken by Eburia pedestris

Another view of the strange pose taken by Eburia pedestris

The strange position did not make a lot of sense to me, but I thought maybe it was a more elaborate way of playing dead, a common behavior in many beetle families (which will probably be featured more than once in this series). I finally decided not to wait for the cerambycid to “open up” so I grabbed it in my hand to put it back into the vial before releasing it outside. And then it hit me.

I mean, it literally hit me.
I felt my hand being pierced in several spots. Blood was dripping from my fingers.
You see, there is a reason why Eburia beetles take this unusual body posture. Look at the beetle’s leg joints and at the tips of the elytra. By taking a “sitting” pose, the beetle transforms into a prickly business, pointing sharp spikes in all directions, making it difficult for large predators like myself to handle the beetle. It will also not hesitate to use its other cold weapon: biting mandibles. Something I only noticed much later when I examined the photos – notice how the beetle contracts its abdomen, to make the elytral spines more prominent. Even with caution it was difficult not to get your skin punctured by the spines. They are as sharp as syringes. I would not want to imagine the experience for a mammal trying to eat this beetle. Ouch.

Longhorn beetle (Eburia pedestris) in defense posture. Grab it if you can.

Longhorn beetle (Eburia pedestris) in defense posture. Grab it if you can.

Some insects prove to us that avoiding predators is not all about hiding, mimicking other organisms, and advertising toxicity or potent venom. There are other, more creative ways to survive in the jungle out there. I will even take it a step further and say this Eburia beetle is comparable to the armadillo girdled lizard in its behavior. Nature is so awesome.

Little Transformers: Ceratocanthinae beetles

If you missed my subliminal message in the last two sentences of the previous post, I am not done yet with the Transformers. I was building up to this exact moment. You see, insecticons ARE everywhere. Maybe not in the same context as depicted on the TV series, but still there are creatures out there that are more than meets the eye. A substantial part of their existence relies on fooling predators into thinking they are something else: an inanimate object, another animal, or something completely different. I am happy to introduce “Little Transformers”, a new section on the blog, in which I will present interesting cases of insects in disguise.

We are launching this series with the beetle that started it all – the pill scarab (member of subfamily Ceratocanthinae). If you run an internet search with the words “transformer” and “insect”, there is a high chance that one of the results will be an image created by Kenji Nishida, showing a small beetle from Costa Rica transforming from a ball-mode to beetle-mode. The image has gone viral soon after being posted online, and now that Ceratocanthus beetle is fairly recognized by title as the beetle transformer. I have posted an image of a similar beetle before on this blog, a Ceratocanthus species I found in Belize. It was featured in an excellent phylogenetic paper about this subfamily by Alberto Ballerio and Vasily Grebennikov, and even made it to the journal’s cover. I recommend checking the paper out, even if you are not interested in these beetles, you can enjoy the beautiful images showing the impressive diversity of the group.

Pill scarab beetle (Ceratocanthus sp.) from Belize, showing the spherical alternative mode typical to members of Ceratocanthinae

Pill scarab beetle (Ceratocanthus sp.) from Belize, showing the spherical alternative mode typical to members of Ceratocanthinae

Ceratocanthinae are a subfamily of Hybosoridae within the Scarabaeoidea beetle group, containing over 360 described species, most of which are small in size (just a few millimeters in length). They have a wide distribution range mainly in tropical regions throughout the world, with only a few genera and species recorded close to temperate regions. Ceratocanthinae also occupy different types of habitats. The highest diversity seems to be in new world rainforests, but they also occur in temperate forests, subtropical forests, savannahs, and even in coastal deserts. Adult Ceratocanthinae are best known for their ability to conglobate: rolling into a nearly perfect ball. The elytra, pronotum, head, and all six tibiae interlock with each other by means of grooves and corresponding ridges, forming a tightly connected external surface. Many beetles take the form of a tight compact structure when threatened, however in Ceratocanthinae the tibiae of all six legs participate in forming the external hard surface of the sphere, unlike in other beetles.

Ceratocanthus sp. transformation sequence from ball-mode to beetle-mode

Ceratocanthus sp. transformation sequence from ball-mode to beetle-mode

It is fascinating to observe these beetles transform to and from their alternative mode. Nancy Miorelli, an entomologist and science communicator living in the Maquipucuna reserve in Ecuador, recently recorded a video showing the beetle opening up (by the way, Nancy also creates beautiful jewelry from insect wings and Tagua nut with the proceedings supporting rainforest conservation and the local community. You can check out her shop here).

Why do they do this? The ability to roll into a tight compact structure probably has anti-predatory and physiological advantages, such as moisture retention or thermoregulation. It seems that the primary use is as a form of crypsis, to avoid detection by nearby predators, however after following several beetles in the wild I noticed that they stay transformed into the ball-mode even when they are not active; perhaps it is a way for them to rest too.

Pill scarab beetle (Ceratocanthus sp.) from southern Belize. Full beetle-mode!

Pill scarab beetle (Ceratocanthus sp.) from southern Belize. Full beetle-mode!

Unfortunately, very little is known about the biology of Ceratocanthinae. They are sometimes found under bark, in tree holes, and in decomposing wood. Several records report adults and larvae that have been found in termite nests. However, It is unclear whether Ceratocanthinae are termitophilous and have a relationship with the termite hosts. The ability to roll into a ball can serve as a defense and might be an adaptation for living in the hostile environment of a termite nest. Another suggestion defines the beetles as termitariophilous, in other words attracted to the properties of the termite nest itself as opposed to its inhabitants. While the feeding habits of Ceratocanthinae are mostly unknown, a handful of observations report adults feeding on various fungi. It is therefore possible that Ceratocanthinae are attracted to some of the fungi growing on the surface of termite nests. This can explain the presence of the beetles in the nests, but unfortunately without additional data about the beetles’ life history it would be difficult to validate this connection.

So the next time you are out in the field and you stumble upon a tiny sphere in a peculiar place, take a closer look. If it looks like a beetle mummy, then bingo! You have a Little Transformer. Now all you need to do is wait for it to open up… Patience. Lots of patience.

From a blattodean to Nilio beetles

This is the story about how a small blattodean taught me something I did not know about beetles.

While photographing frogs in the Ecuadorian Amazon this past October, I noticed a tiny insect running across the surface of a fallen leaf resting on the forest floor. It had bright colors and looked interesting, so I collected it in hopes to photograph it later. When I finally got to do it, I was struck by its deception. You see, when I initially spotted it I thought it was a beetle. The dome-shaped body and the bright coloration resembled those of some leaf beetle species (family Chrysomelidae), and this insect even moved and walked like a beetle. Nevertheless, a close inspection revealed that its whole body was segmented. This was no beetle. It was a blattodean nymph.

Beetle-mimicking cockroach nymph

Beetle-mimicking cockroach nymph

Beetle-mimicking cockroach nymph. What could be the model species?

Beetle-mimicking cockroach nymph. What could be the model species?

Beetle-mimicking cockroach nymph

Beetle-mimicking cockroach nymph

Blattodeans exhibit some beautiful examples for mimicry, with some species resembling poisonous fireflies and venomous assassin bugs. It should come as no surprise that a blattodean might benefit from looking like a leaf beetle. While many leaf beetles are harmless, some species harbor chemical compounds that make them poisonous or distasteful to predators. Unfortunately, identifying a blattodean from its larval stage is very tricky and close to impossible. I was not able to locate anything that looked like the adult stage of this species. However, when I examined this cute blattodean I remembered that I have seen this color scheme on a leaf beetle before, and after digging in my old photo archive I was able to find the record.

Leaf beetle. Or is it?

Leaf beetle. Or is it?

I took this photo on one of my first visits to Ecuador, over a decade ago. I did not plan to do anything with the photo, but I thought it was a nice-looking leaf beetle and so I snapped a quick photo for my own records. Only I was completely off. This is not a leaf beetle.

Unlike most of its family members that are elongated and dull-colored, Nilio is a genus of darkling beetles (family Tenebrionidae) that bear a striking resemblance to leaf beetles and ladybugs. This resemblance can fool even experienced entomologists. Darkling beetles are well-known for their chemical defense, secreting odorous chemicals that will deter even the most enthusiastic field entomologist. This can explain the blattodean mimicry shown above.

This is not a leaf beetle but a darkling beetle (Nilio sp.)

This is not a leaf beetle but a darkling beetle (Nilio sp.)

After I realized these photos show a species of Nilio, I checked the rest of my photos from the very same trip, and started finding more photos of Nilio species.

Darkling beetle larvae (Nilio sp.) feeding on lichens

Darkling beetle larvae (Nilio sp.) feeding on lichens

Here is a group of larvae on a branch. Nilio larvae are gregarious (live in groups) and feed on epiphytic lichens. If you have ever seen the typical wire-worm larvae of darkling beetles you will understand why I labeled this photo as “chrysomelid larvae” in my archive.

Darkling beetles (Nilio sp.) aggregating next to pupation site

Darkling beetles (Nilio sp.) aggregating next to pupation site

In some species, not only the larvae, but also the adults, are gregarious. Here is a group of adults I found on a tree trunk close to their pupation spot. Like the larvae, these adults were feeding on lichens as well.

A closer look at the Nilio beetles aggregation

A closer look at the Nilio beetles aggregation

As you can see, not all Nilio species have bright coloration as the species shown above. However, even when they are closer to their “darkling roots” they still look more like to members of Chrysomelidae than Tenebrionidae. This all goes to show that even when you are confident about your knowledge of insect taxonomy or biodiversity, nature can still surprise you. I embrace these moments when I am caught unprepared; nothing like learning something new!

Two horned darkling beetle – Neomida bicornis

Last week I met with Catherine Scott and Sean McCann, two talented naturalists and spider-enthusiasts (Catherine studies the mating behavior of black widows, and if you haven’t already, I recommend following her live tweets from experiments). It was great to go hiking together in the snow-covered woods, looking for arthropods hidden inside fallen logs. Before we went on the hike, they brought me a few entomological presents, one of them were lovely beetles that they found during a trip a week earlier.

A pair of two-horned darkling beetles (Neomida bicornis). Ontario, Canada

A pair of two-horned darkling beetles (Neomida bicornis). Ontario, Canada

These magnificent beetles are Neomida bicornis, a species of fungus-feeding darkling beetles (family Tenebrionidae). They are tiny, measuring only a couple of millimeters in length. To the untrained eye they do not even look like darkling beetles, these beetles are like jewels! Their body is very shiny, metallic green in color. The elytra have a bluish tint. Populations of Neomida bicornis in southern North America have an orange pronotum (a true feast of colors, for a darkling beetle at least). The males are characterized by four horns, two of which prominent between the eyes, and two smaller ones on the clypeus (=lip area) above the mouth. The females have no horns. I admit, I have a soft spot for horned insects. What a fabulous gift, thanks again you guys!

These beetle are tiny! That’s the tip of a regular ruler with a millimeters scale.

The female two-horned darkling beetle (Neomida bicornis) is hornless

The female two-horned darkling beetle (Neomida bicornis) is hornless

This species is not rare, but its way of life makes it hard to find: the adults and larvae feed on bracket fungi (polypores) and burrow into this tough substrate, creating inner galleries. According to Sean, these beetles were active inside the mushroom despite the somewhat low ambient temperatures. From what I learned about eastern North American fungus-feeding tenebrionids, they have overlapping generations. In other words, both adult beetles and their larvae can overwinter inside the mushrooms. I will probably try to confirm this at some point but first I need to find out how the larvae look like. They are not the only arthropods taking advantage of a polypore-type shelter from the cold weather.

Male two-horned darkling beetle (Neomida bicornis) inside a polypore mushroom

Male two-horned darkling beetle (Neomida bicornis) inside a polypore mushroom

You cannot afford to buy this image

Several articles about Epomis that have been published over the last few months triggered an increase in public interest and the beetles’ popularity, followed by an avalanche of requests for image use from magazines and news agencies. I should be happy about this, if not for the small fact that most of these requests are for free or discounted images. I avoid mentioning anything about pricing for my photos here on the website. It is not that they are not for sale, on the contrary. My pricing is pretty standard for a wildlife photographer these days, and I even dare say it is competitive compared to stock agencies and other photographers’ rates. At this moment, I prefer to handle licensing requests on a case-to-case basis. I know that at some point, maybe when more people show interest, I will set up an e-commerce website offering prints.

That being said, I take the aspect of rarity into account when calculating my pricing. If my photograph shows a rare event, an unusual phenomenon or something other photographers are less likely to capture, I charge a higher rate. I admit that as of now I only have a handful of such photos, and as you might expect, some photos of Epomis beetles fall under this category. Case in point:

European green toad (Pseudepidalea viridis) being lured to hunt and getting attacked by a larva of Epomis dejeani. Several news agencies, while completely ignoring my pricing, requested to license this photo for what I can only call - pennies.

European green toad (Pseudepidalea viridis) being lured to hunt and getting attacked by a larva of Epomis dejeani. Several news agencies, while completely ignoring my pricing, requested to license this photo for what I can only call – pennies.

Why do I rate these photos differently from the rest of my portfolio? Wouldn’t it be wiser to charge the same rate for each image? Pricing photographs is a bit of a controversial topic. While I will not go into pricing standards, many pro photographers agree that there is nothing more insulting than receiving requests from commercial entities for free images. Some of us already have our photos spreading through the internet after being stolen (Click here for an example. Unfortunately for me I was too late to stop this one from spreading). On the other end of the spectrum there are photographers who are happy to give photos away for a simple credit mention. I try not to judge, but I honestly cannot understand this approach. There is a lot involved financially when one decides to pursue professional photography. I love this analysis by John Mueller:

“It cost me $6,612 to take this photo.
$12 in gas to go from work to this spot and then home. The camera I took this with cost $2500. The lens was another $1600. The Singh Ray Reverse Neutral Density filter was $210. The Lee Wide-Angle Adapter and Foundation kit was another $200. The Slik Tripod was another $130. The shutter-release was another $60. When I got home, I uploaded it to a computer that cost me $1200, and then I used Lightroom 3 which I got for $200. I then exported it and tinkered with it in Photoshop which costs about $500.”

OK, maybe this is a little too extreme. If I took this approach to calculate the rate for my Epomis photo, including gear and traveling costs (this photo was taken in Israel after my relocation to Canada, so there was quite a bit of traveling involved) it would easily reach over $10K. Instead, let’s keep it simple, and I will include just one aspect that is frequently missed when reviewing photographs – time.

To most people, a photo is merely a click of a button. A perfect moment captured in time. However, I hold a slightly different opinion, which I expressed briefly in this post. You see, it took me two years to take the above photo. And I am saying this while omitting the +5 years I have been studying Epomis beetles, which gave me excellent insights on where and when to find them in the field. Knowing your subject is the key to getting good shots in the wildlife photography genre, yet it still took me another two years to get the shot. Why? This is where photographic technique comes into play. I planned this shot in my mind way before I traveled back to Israel to search for my subjects. I had to know exactly where to position and how to diffuse my lights, which moment to press the shutter, and for months I perfected my technique so that when I get to that decisive moment, in which I have only a split second to record the predation interaction, it would go as smooth as possible. And you know what? Even after all this planning it still took a few attempts to get the sequence the way I wanted it.

To summarize this rant, my hard-earned knowledge and level of expertise are not up for grabs. Definitely not at a discounted rate. Oh yes, this particular photo also consists of four different exposures. Maybe I should have mentioned this as well.


UPDATE (11 Mar, 2016): In the last 24 hours this post received a lot of attention, sparking an interesting discussion on FaceBook. After reading some of the comments, I want to clarify a few things:

* The pricing calculation that appears in quotes is NOT my pricing. I only brought it as an example to show the level of financial investment for the professional photographer. If you read on, you learn that I am more realistic and do not price my photos this way.

* I know I made it sound like I never allow to use my photos free of charge but I assure you this is not the case. For most personal use, in-class educational use and scientific presentations I do not charge a fee. Other non-profit use is evaluated on a case-to-case basis, but I am very flexible in my terms. If I supply high quality photos I expect to receive something equal in return, it does not have to be currency; in the past I received books, gift cards, bits of gear, accommodation and even research support in exchange for my photos.

* Also, it is OK if you do not agree with my opinion. If you want to give your photos away for free, go ahead. I do not like it because it causes depreciation of other photographers’ work, but I cannot stop you. However, if one day you choose to start viewing your creations as valuable and decide to charge a fee for their use, making that transition from charging nothing will be hard for you, take it from someone who has been in that stage.

Bombardier beetles – explosions of smoke in your face

I was very positively surprised by the response to my previous blogpost about Epomis. In fact, it now seems that this post is the most popular one on the blog, even more than the ones about the botfly and my NZ accident. How do I top it? Only time will tell. In the meantime, I wanted to mention some of the other ground beetles (family Carabidae) that share the habitat with Epomis. You see, when you start flipping stones and pieces of wood scattered around rain-pools you encounter many carabids. But one group really stands out in appearance, and, as much as it is hard to believe, in sound: the bombardier beetles.

Bombadier Beetle (Brachinus crepitans), one of the cutest species of ground beetles. Golan Heights, Israel

Bombadier Beetle (Brachinus crepitans), one of the cutest species of ground beetles. Golan Heights, Israel

An aggregation of several beetle species found under a rock. Bombardier beetles (Brachinus alexandri) can be seen on the right. Also appearing in this photo: Chlaenius aeneocephalus (Carabidae, metallic colors), and Cossyphus rugulosus (Tenebrionidae) - beautiful beetles camouflaged as seeds! Central Coastal Plain, Israel

An aggregation of several beetle species found under a rock. Bombardier beetles (Brachinus alexandri) can be seen on the right. Also appearing in this photo: Chlaenius aeneocephalus (Carabidae, metallic colors), and Cossyphus rugulosus (Tenebrionidae) – beautiful beetles camouflaged as seeds! Central Coastal Plain, Israel

Bombardier beetles is a large group comprised of several Carabidae tribes. Here I refer mainly to species of the genus Brachinus. These are small to medium sized beetles, usually with striking aposematic coloration: the body and limbs are bright orange, while the elytra (wing covers) are usually dark green or brown, sometimes with a metallic sheen. These colors serve as a reminder for potential enemies that these beetles can deploy a powerful weapon: an explosion of hot chemicals, which can be aimed at almost any direction.

Two common species of bombardier beetles from Israel: left - Brachinus alexandri; right - Brachinus berytensis

Two common species of bombardier beetles from Israel: left – Brachinus alexandri; right – Brachinus berytensis

Much has been written about the mechanics and evolution of the beetles’ chemical defense. In short, when provoked the beetle releases two chemicals, hydroquinone and hydrogen peroxide, into a chamber in its abdomen. This mixture, when comes in contact with a catalyst, turns highly combustible due to the oxidation of hydroquinone and the breakdown of hydrogen peroxide to oxygen and water. The chemical reaction starts inside the chamber with temperatures reaching 100°C, and the high-pressure buildup causes the explosion. Then all the beetle has to do is to aim its “nozzle” and fire! The result is a smoke cloud of chemicals at extremely high temperatures. It can momentarily paralyze or even kill arthropod enemies, such as ants and spiders. To us humans (=entomologists who collect the beetles with bare hands) the damage it causes is not so severe, usually nothing but a small stain of burnt tissue, but the effect is coupled with a startling popping sound, and that might be enough for the beetle to escape from a large predator. This complex defense mechanism was used by creationists as an example for intelligent design in debates against evolution. However, it can be easily demonstrated that by gradually increasing the concentration of hydrogen peroxide this defense could evolve in incremental steps without risking the beetles’ existence. If you are still confused, I highly recommend watching Richard Dawkins explaining it here.

Damage to skin caused by bombardier beetle (Brachinus berytensis) chemical defense

Damage to skin caused by bombardier beetle’s (Brachinus berytensis) chemical defense. Not much.

I feel that I must stop here for a brief public service announcement: There are several videos showing the beetle’s defense (you can google them), almost all of them depict the beetle being held in place with either glue or a pair of tweezers. I would like to argue that unless this is being done for research purposes, these actions border on animal cruelty. Sure, it is strange to hear such a statement coming from someone who fed live amphibians to beetles. Still, I want to stress that in the case of the bombardier beetles this is highly unnecessary. The beetles will still put up the same “show” if poked or gently lifted, without causing them much stress and damage, as can be seen from this short video I took almost a decade ago (I mean it, this is a really old video, so please do not judge the quality):

The species shown in the video is Brachinus bayardi, one of the largest species found in Israel:

Bombardier beetle (Brachinus bayardi), Central Coastal Plain, Israel. These beetles are strictly nocturnal, and can be found running on muddy banks of rain-pools in search of prey.

Bombardier beetle (Brachinus bayardi), Central Coastal Plain, Israel. These beetles are strictly nocturnal, and can be found running on muddy banks of rain-pools in search of prey.

While the chemical defense of the bombardier beetle alone is interesting enough, there is another aspect in their life history that is fascinating. In most species, the adult bombardier beetles are predators of small, soft-bodied invertebrates, but as larvae they feed solely on pupae of other beetles found in the same humid habitat, usually diving beetles (family Dytiscidae) and water scavenger beetles (family Hydrophilidae). This makes them parasitoid insects – their larvae are completely dependent on another insect for completion of their development, usually with fatal consequences to the host. While most parasitoid insects are wasps and flies, in beetles this way of life is relatively uncommon, with only a handful of beetle families exhibiting a parasitoid life history. Despite searching for years, I have yet to find larvae of bombardier beetles, and my attempts to obtain larvae from captive adults has failed so far. I hope this will change one day.

Epomis beetles – insect response to amphibian tyranny

You can say that I am a little obsessed with Epomis beetles. Can you blame me? They are fascinating creatures. It suddenly dawned on me that since the launch of this blog I have not written a single word about the beetles. Unfortunately, there is a lot of misinformation and inaccuracies on the internet, and even in reputable magazines and books featuring Epomis.

It is one of the weirdest animal stories, one in which a small and seemingly harmless animal prevails against a much bigger animal. A unique case of predator-prey role reversal, where the would-be predator becomes the prey. Amphibians, such as frogs, typically prey on insects including ground beetles and their larvae. Among these beetles, one genus managed to stand out and deliver a proper counterattack to its predators. The Epomis larva has impressive double-hooked mandibles that look like they came right out of a horror movie. It waves them around along with its antennae until the movement attracts a hungry amphibian, which approaches quickly and tries to eat the larva. In a surprising turn of events, the larva is able to dodge the predator’s attack only to leap on the unsuspecting amphibian and sink its jaws into its flesh. It then continues to feed on the amphibian, sucking its body fluids like a leech at the initial stage, and eventually consuming it completely. Sounds like science fiction, I know. But it is real. Furthermore, these larvae feed exclusively on amphibians, and refuse to eat anything else. They are dependent on amphibian prey for completion of their development. This makes the predator-prey role reversal an obligatory one, which is very rare in the natural world.

First instar larva of Epomis circumscriptus showing its double-hooked mandibles.

First instar larva of Epomis circumscriptus showing its double-hooked mandibles.

I first learned about Epomis beetles in 2005, when I was working in the Natural History Collections at Tel Aviv University in Israel. They ended up being a great topic for my M.Sc thesis research, and I continue to study them to this day. The genus contains about 30 species distributed in the old world, with the African continent as the center of diversity. They inhabit the banks of rain-pools and temporary ponds, and synchronize their breeding season with amphibians’ metamorphosis into the terrestrial stage. Most of what we know about Epomis comes from studying three species only (in other words, there is more unknown than known). When the main paper from my thesis was published in late 2011, it became an instant hit in the media (see below). However, one main point of criticism was that the supplementary videos showed the interactions between Epomis and amphibians in a lab setting, which might have triggered an unnatural behavior from both. This is a valid point. We needed a controlled environment to test and prove beyond disbelief several hypotheses regarding the feeding habits of Epomis. Nevertheless, I spent the following years going back and recording the same interactions in the field.

Here is a larva of Epomis circumscriptus displaying luring behavior while waiting for a passing amphibian:

And this is the outcome of the above scenario:

 

To better understand what is happening during this swift encounter, here is a break down of this interaction to several simple steps. As you can tell by the above video, this sequence takes only a split second in real-time:

From enticement to desperation: European green toad (Pseudepidalea viridis) being lured to hunt and getting attacked by a larva of Epomis dejeani. View large!

From enticement to desperation: European green toad (Pseudepidalea viridis) being lured to hunt and getting attacked by a larva of Epomis dejeani. View large!

The larvae are terribly good at this. Even if they are caught by the amphibian’s tongue, they are still able to quickly use their mandibles to grab the amphibian from the inside, whether it is the throat or stomach, and start feeding.

Hard to believe, but this toad is being eaten.

Hard to believe, but this toad is being eaten.

Sometimes the amphibian accidentally steps on the Epomis larva. In this case, the larva will attach to the leg. First instar larva of Epomis dejeani feeding on a Lemon-yellow tree frog (Hyla savignyi).

Sometimes the amphibian accidentally steps on the Epomis larva. In this case, the larva will attach to the leg. First instar larva of Epomis dejeani feeding on a Lemon-yellow tree frog (Hyla savignyi).

While the larvae are specialized amphibian ambushers, the adult Epomis beetles are somewhat more generalist predators. They prey on other arthropods and will sometimes go for the occasional earthworm. But these feeding habits only last until they stumble upon an amphibian again. Then, a hidden memory back from the days they spent as larvae kicks in, and they set out to relive their glory days as amphibian slashers.

Epomis dejeani attacking a European green toad (Pseudepidalea viridis) while holding firmly to avoid falling off. Compare to the photo of the larva attached to the leg above.

Epomis dejeani attacking a European green toad (Pseudepidalea viridis) while holding firmly to avoid falling off. Compare to the photo of the larva attached to the leg above.

In a blink of an eye, the beetle sneaks up on the amphibian and pounces on it, holding firmly to avoid falling off. It then moves to the back, and like scissors uses its mandibles to make a horizontal incision, which disables the hind legs and ultimately prevents the amphibian from escaping. As if this was not gory enough, both adult beetles and larvae are particularly fond of eating the amphibian’s eyes. It is like a sick twist of revenge for the insects: after millions of years of suffering under the constant threat of predation by amphibians, they are able to fight back. Not only they hunt their potential predators and slowly eat them alive, but they also cripple them and peck their eyes out right from the start.

Remains of a partially eaten amphibian in the vicinity of temporary ponds are usually a good sign for adult Epomis activity in the area. Central Coastal Plain, Israel

Remains of a partially eaten amphibian in the vicinity of temporary ponds are usually a good sign for adult Epomis activity in the area. Central Coastal Plain, Israel

Epomis dejeani guarding a recently captured European green toad (Pseudepidalea viridis). The beetles can get very territorial over prey items.

Epomis dejeani guarding a recently captured European green toad (Pseudepidalea viridis). The beetles can get very territorial over prey items.

How did this phenomenon evolve? To be honest, we do not know exactly. But it is possible that somewhere in the evolutionary past, Epomis beetles used counterattack behavior, instead of escaping, as a defense against amphibians. Such behavior could have later evolved into exploiting amphibians as a source of food. The amphibians probably could have not evolved to recognize and avoid this behavior because the majority of insect prey they encounter poses no threat to them, as opposed to the relatively uncommon Epomis beetles. Another interesting point, is that both adults and larvae of Epomis lack any venom, yet the amphibian is quickly subdued and stops resisting after being caught, even while it is slowly being devoured alive.

One common reaction that I get in response to this study is that it was “cruel”, involving poor helpless amphibians that were sacrificed in the name of science. Some people even go further to suggest that I am a sadistic scientist somehow enjoying this. It could not be farther from the truth: This is a natural phenomenon and Epomis beetles must kill and consume amphibians in order to exist. Nature is cruel. We tend to think of amphibians as cute and helpless animals, but from the insects’ perspective they are actually cold-blooded killers (pun intended), gulping every small creature in their path. Moreover, the reality of this study is even harsher: the amphibians would have still died even without me using them as food for Epomis, because the puddles they were found in as tadpoles were quickly drying out. As for myself, I cannot begin to describe the emotional stress I suffered during this research, just so I could bring Epomis’ fascinating biology to the spotlight. I love amphibians, and it was disheartening for me to watch them die so many times. Throughout the study I kept telling myself: “I am going to hell for this, no doubt about it”.

In the past few years I have been following the response to the story of Epomis beetles. More sightings of the beetles are being reported from around the world. There are some excellent blog posts (1,2,3,4, and do not miss Bogleech!), news reports (1,2,3,4,5), videos and TV segments, radio interviews and podcasts, and even Wikipedia pages. Epomis has found its way into artwork. There is a metal band named after the beetles. It is very possible that this is the discovery I will go down in history for, and that is fine by me. Hollywood, I am waiting by the phone for your call. To end this post on a positive note, here is a fitting limerick that I love, written by the talented Celia Warren:

Of the genus Epomis, folk say,
Their larvae at first seem like prey,
But they’ll bite a frog’s throat,
Leave it paralyzed, note!
Then they’ll eat it without more delay.


UPDATE (8 Feb, 2018): I decided to add a gallery page dedicated to Epomis beetles. You can find it here.