parasites - Gil Wizen

The Plot Thickens: This caterpillar ain’t big enough for the two of us

Some of my favorite insects to find while out in the field are hawkmoth caterpillars, or hornworms (named after the characteristic “tail”). They are big, squishy sausages that often show off dazzling colors, sometimes with interesting anti-predator adaptations like eyespots and mimicry. All these characters make the hawkmoth caterpillar look like a toy just waiting for you to play with. The sad truth is that being big and flashy in the natural world often comes with a price. There is danger lurking in every corner. Despite the bright colors and adaptations, birds and lizards do not hesitate to snatch the caterpillars from branches, pathogens and spores of entomophagous fungi scattered everywhere increase the chance for passive infections, and parasitoids are always on the lookout for chunky hosts for their offspring. And the reality is that many of the caterpillars we get to encounter outdoors are already infected with something. I learned this the hard way: as a kid I used to rear a lot of butterflies and moths collected as caterpillars in the field, and many times I was devastated to witness my cute pets being reduced into a sticky mess while wiggly worm-like creatures emerge from their bodies. Sometimes I wonder how lepidopterans manage to keep their populations stable with so many enemies around.

On one of my visits to the beautiful town of Mindo Ecuador, I came across a young hornworm. Despite finding it at daytime, the caterpillar remained calm (many hornworms do their best to disappear from plain sight during the day) so I decided to photograph it.

A cute hawkmoth caterpillar. See that black spot on the leaf? It is important to our story.

After taking a few shots I noticed a black splotch in the photo that I didn’t like, so I decided to change the angle of view. Little did I know this was a wasp that just arrived at the leaf to check out the caterpillar. A few photos later its identity became clear: It was a species of Brachymeria, a tiny wasp that belongs to the large parasitoid family Chalcididae.

The hawkmoth caterpillar being visited by a parasitoid chalcidid wasp (Brachymeria sp.)

Chalcidid wasps can be easily recognized by their modified hindlegs that resemble mantids’ raptorial forelegs. The function of these structures is largely unclear. The adult wasps feed on nectar and other liquid foods, and do not use the legs for catching prey. There is a paper describing an interesting behavior in which the females use their legs in fighting over a host’s egg mass. Even more interesting are the last three paragraphs of the paper, with additional examples and hypotheses. It seems like there is no single function for these modified hindlegs and it really depends on the species and its biology. One example really stands out: “The female of Lasiochalcida igiliensis literally jumps into the jaws of antlions and holds the mandibles agape with her hind legs while ovipositing.”

Going back to our little Brachymeria and the hawkmoth caterpillar, at first the wasp just strolled peacefully on the leaf next to the caterpillar, but within a few minutes it hopped, quite literally, on the caterpillar and started walking on it, exploring its body surface while frantically moving its antennae.

The wasp jumped on the caterpillar’s proleg and started crawling on its body

In general, the caterpillar doesn’t enjoy this attention, and often swiftly moves its head backwards in an attempt to drive the parasitoid away. It usually does not work. Once a caterpillar has been spotted and marked by a parasitoid as a host, it will be attacked (here’s a fantastic video showing this behavior, notice that the fly sitting nearby is another parasitoid of hornworms – a tachinid fly!).

A closeup of the parasitoid chalcidid wasp (Brachymeria sp.) as it was walking on the hawkmoth caterpillar

As I was taking photos of the tiny wasp antennating the caterpillar, from the corner of my eye I noticed a bright yellow object flashing in. A second wasp, a golden Conura species, swooshed into the scene and started harassing the busy Brachymeria wasp.

While the Brachymeria was busy exploring the caterpillar, another wasp (Conura sp.) rushed in to fight for it

For a short while, the Conura striked from above repeatedly, yet the Brachymeria stood her ground. Eventually the Conura got fed up and attempted to grab onto the other wasp and pull her away from the host. After several tries she succeeded, and the two started swirling in the air, before the Brachymeria returned to her business on top of the caterpillar. The golden wasp did not give up and returned for a second attack and then a third.

The two chalcidid wasps (Brachymeria sp. and Conura sp.) fighting over the host. This was taken moments before the Conura grabbed the other wasp’s head and dislodged it from the caterpillar.

This was very exciting to watch, but to be honest I was waiting eagerly to see if the wasps would use their modified hindlegs during the fight. Unfortunately, I was not able to detect any special maneuvers that involved grabbing with those legs.

Why did this happen? There are several possible explanations. The simplest one is that there is a shortage of caterpillar hosts and the two wasps are competing for the same source of food for their larvae. However, an alternative explanation suggests that the caterpillar has already been infected with a parasitoid before the first wasp found it. Many chalcidid wasps are hyperparasitoids – they do not feed on the big hosts (the caterpillar) directly, but instead attack larvae of other parasitoids already feeding inside the host. In other words they are parasitoids of parasitoids.
Parasitoidception.
Watch this excellent video explaining the complex relationship between several wasp species living on a tobacco hornworm:

This can explain the intense antennation performed by the Brachymeria wasp on the caterpillar for a long period of time. Maybe the wasp was trying to determine if there are parasitoid larvae already present in there. One of the most common sights when it comes to infected hawkmoths is a caterpillar with a cluster of white silk cocoons dangling from its body. Those cocoons belong to braconid wasps, and there is a good chance that the Bracymeria wasp was after their larvae, as some species of in the genus are parasitoids of Braconidae. The golden Conura wasp could then compete for access to those parasitoid larvae or even go after the Brachymeria larvae. It can get pretty complicated with chalcidid wasps.

Hawkmoth caterpillar with cocoons of a braconid parasitoid wasp. The caterpillar is still alive, and can move its head to deter predators like ants and other parasitoids from approaching the developing wasps.

So who won in the end? The wasp that was more persistent. At the end of the fight the black Brachymeria wasp was nowhere to be seen, and the golden Conura wasp took over the caterpillar and started antennating it.

The winning chalcidid wasp (Conura sp.) with its hawkmoth caterpillar prize

The interesting thing here is that members of genus Conura are usually associated with butterfly and moth’s pupae, yet the wasp here decided to chase off a competitor and take over a caterpillar.

Chalcidid wasp (Conura sp.) on a swallowtail butterfly pupa

Chalcidid wasp (Conura sp.) on a swallowtail butterfly pupa. This innocent face hides a dark secret.

Unfortunately, I had to leave the scene to catch a bus so I could not continue following this interaction. Without further observations, it is difficult to say with certainty what exactly was going on between the two wasps and the hawkmoth caterpillar. Parasitoids are so diverse, and many species have such complex biology. Even though several chalcidid wasp species are being studied closely as potential biological control agents, there are far more species out there about which we simply don’t know enough!

The Plot Thickens: Staring into the eyes of a dying Cephalotes

If you are an entomologist or an insect enthusiast, it is highly probable that you like ants. It is hard not to be impressed with their diversity, abundance, complex social structure and behaviors, as well as their interactions with other organisms. Ants are everywhere and do almost anything you can think of. To most people however, ants could not be any less exciting. They are often seen as a generic insect, with a relatively uniform appearance. They always show up when unwanted, find their way into our homes, take refuge in dark and hard to reach corners, and steal our food.
I like ants. I think they are fascinating creatures. But every now and then I find myself talking people into looking beyond “that boring-looking ant”, to try and catch a glimpse of their busy life. It is not always easy to communicate ants to the public (which is why I praise myrmecologists – people who study ants for a living), however I find that it is quite easy in the case of one ant genus in particular: Cephalotes.

Turtle ant (Cephalotes atratus) from the Ecuadorian Amazon

Cephalotes is a large genus of arboreal ants found in the neotropics. There are over 130 species, all inhabit tree hollows or utilize cavities in other plant tissues. Looking like they were designed by someone with overflowing imagination, they easily come off as cute. Their flattened head and armored body, often decorated with long sharp spines for protection, their thick legs and perfectly round abdomen, along with their matte color finish, give them the appearance of a plastic toy. In addition, Cephalotes ants move relatively slowly and cannot bite or sting, making them user-friendly. Can you ask for a more perfect ant?

The queen turtle ant (Cephalotes atratus) is bigger and bulkier than her workers. She also lacks the defensive spines.

Turtle ant worker (Cephalotes atratus) foraging on a mossy tree trunk

They are commonly known as turtle ants, but also got the name gliding ants, thanks to their incredible ability to parachute from high in the canopy and land back on the trunk of their home tree. Their unique body structure and flattened legs allow them to slow down and change their course while falling (some spiders can do the same, by the way). In some species the soldier cast evolved a large head to function as a living door, plugging the entrance to the nest.

Turtle ant soldier (Cephalotes sp.) from Colombia, showing a heavily armored body and a massive head

The same turtle ant soldier (Cephalotes sp.) from the previous photo. These ants are built like tanks.

In regards to interspecific interactions, Cephalotes ants are often seen tending sap-sucking hemipterans such as membracids and small fulgorids to gain access to sugary secretions from those insects. They also act as the model in a mimicry complex, where crab spiders masquerade as the ants in order to sneak up and prey on them.

Cute Cephalotes workers visiting a camouflaged fulgorid planthopper nymph

Portrait of a turtle ant (Cephalotes atratus). How can you not fall in love with them?

Did I mention they are cute? I have written before that you should never become too attached to insects you encounter in the field. And as much as I love the adorable Cephalotes ants, it is important to remember that there are many dangers lurking for them in the forest. During my recent trip in Colombia, I stumbled upon a Cephalotes nest in a tree outside my room. The ants were very active and did not present good photographic opportunities.

Turtle ant (Cephalotes sp.) from Colombia. How adorable!

One of them however, stood out among the rest. There was something different about its behavior. This worker moved franticly in what appeared to be an aimless run. It did not follow the other workers, and seemed more interested in reaching a higher spot on the tree. I collected the ant for a closer look, and once I inspected her carefully I believe I found the culprit for her unusual behavior. This ant had a reddish abdomen, as opposed to the black abdomen of her sisters. The red color, coupled with erratic behavior suggests this worker has been infected with a parasite, a nematode worm.

Turtle ant (Cephalotes sp.) infected with a parasitic nematode worm, showing a swollen red abdomen. Compare to the healthy worker in the previous photo.

The parasitic worm lives and breeds inside the body of birds, which spread the worm’s eggs in their droppings. The ants collect nutrients from the bird droppings (along with the eggs) and feed them to their larvae, where the worm matures. In order to complete its life cycle the parasite needs to return into a bird’s body, so it changes the host ant’s appearance to look like a ripe red fruit, and causes it to climb higher on the tree to become more accessible to hungry birds. As much unique character this worker ant might have had, the sad truth is that it was destined to die prematurely. And there was nothing I could do about it. There is a great lesson here – sometimes, the raw essence of nature is difficult to take in. We would like to see it as a peaceful place where all the animals and plants live together in harmony. But the reality is that nature is harsh. It is full of conflict, violence, disease, and death. And we must accept it as an integral part of the world we live in.

Cephalotes ants offer a great opportunity to peek into the life of a small insect and learn about its survival (as well as failure) in various habitats. Before I end this post, there is one thing I would like clarified – going back to their name, why did Cephalotes get the name turtle ant, whereas some leaf beetles were named tortoise beetles? Is there any justification for the turtle designation when it comes to the ants? After all, both insects are terrestrial. If there is an etymologist in the audience, maybe you can help the entomologist?

Little Transformers: Forcipomyia, the midge that turns into a balloon

It is time to introduce another Little Transformer! I know what you are thinking. Am I ever going to run out material for these blog posts? Maybe. Probably not. As long as there are arthropods around, their life history and morphological diversity guarantees that I will always find examples for interesting deceptions and transformations. Up until now I mostly focused on animals that can change form quickly, assuming the appearance of something else as a defense response against predators and to avoid detection. The case presented in this post is a little different because it does not follow a quick change of form, but rather a slow one, over the course of a life stage. I should be cautious here, because under this definition every insect that goes through complete metamorphosis from larva to adult can be considered a Little Transformer (butterflies, beetles etc’). Even amphibians fall under this loose definition. And to some extent they ARE transformers, because the changes they go through during development are extreme. But this is not the topic for this series of posts. When I talk about a big change happening within a life stage, I mean that the animal starts as one thing, and by the end of the stage its appearance and function has changed into something else completely. And no example is better to show this than the parasitic midges of the genus Forcipomyia.

Biting midge (Forcipomyia sp.) feeding on the hemolymph of a moth caterpillar. Photographed in Belize

Here is the Forcipomyia midge with the whole caterpillar to give a better sense of scale

Forcipomyia is a large genus in the midge family Ceratopogonidae, with a worldwide distribution and diverse habitat preferences. There are now over 1,000 described species of Forcipomyia. The adults of some species are known as important pollinators of cacao and other plants of economic importance in tropical and subtropical areas. However, many species in the genus are blood-feeders, somewhat characteristic to ceratopogonids as the common name to the family suggests (biting midges). These parasites have interesting relationships with different insect hosts, and they can be found feeding on the hemolymph (insect blood) of grasshoppers, katydids, stick insects, butterflies, true bugs, and even skittish dragonflies. In fact, these interactions are so fascinating and overlooked, that only after spending some time in the field one can notice the midges have a preference for certain host species to feed from.

Sometimes the biting midges sneak into the photo without me noticing. I photographed these mating grasshoppers (Cloephoracris festae), but they have an accompanying Forcipomyia. Can you spot it?

But let’s go back to the transformation they go through, because in one group of species, subgenus Microhelea, it is truly remarkable. The female Forcipomyia midge begins her adult stage with an active lifestyle. She flies about in the forest, feeding on nectar from small flowers. As days go by, she starts craving for blood and search for insects to bite. When she locates her preferred host, using her serrated mouthparts she proceeds to bite it in an area that has soft tissue: antennae, legs joints, wing veins, or between body segments. Once she found the right spot that will fulfill her dietary needs, the female midge attaches to it firmly, and… doesn’t let go, thanks to specialized claws on her feet. She sucks and gulps the insect’s blood, filtering the nutrients and secreting the excess fluids as clear droplets.

Tick fly (Forcipomyia sp.) feeding on the hemolymph of a walking stick

The midge stays attached like this for quite a while, and soon this sessile lifestyle starts taking its toll on the small parasite. She starts to put on weight. Then, she usually loses her wings – she will not need them anymore because the added mass from the developing eggs prevents her from taking off.

Female Forcipomyia swelling while feeding. She lost her wings but can still use her legs to hold firmly onto the host

Forcipomyia getting fatter… but not quite there yet

As she continues to swell like a grapefruit, the Forcipomyia midge also losses the ability to use her legs. She does not need to leave anyway, but she is so bloated that she cannot even hold onto the body of the host, and the only thing keeping the two connected are the midge’s mouthparts.

Female tick fly (Forcipomyia sp.) at the final stage of feeding. Her legs released their grip on the host and at this point the midge has fully transformed into a passive parasite that looks like a balloon.

Stick insect (Pseudophasma bispinosum) carrying tick flies (Forcipomyia sp.) at different stages of feeding. Photographed in Ecuador

At this point, the engorged biting midge is no different than a tick, and indeed many refer to these parasitic Forcipomyia as tick-flies. Sometimes I like to imagine these fat dipterans disconnecting from their host and floating upwards like a balloon filled with helium, reaching above the forest canopy and flying into space. In reality, the exact opposite happens. The Forcipomyia female eventually leaves the host and drops to the ground, where she lays her eggs and finishes her role. And the male Forcipomyia? They are mostly unknown. Because males are never found feeding on insect hosts, it is safe to assume that they do not feed on blood, and prefer to keep a vegan diet of sweet nectar.

An engorged female tick fly (Forcipomyia sp.) after dropping from its host

Tick fly (Forcipomyia sp.) engorged with hemolymph viewed from above

What about the larvae, are they parasites too? The majority of the research on biting midges has focused on the adults, due to their economic and medical significance, as well as their important role in aquatic ecosystems. Larvae of most ceratopogonids are unknown because finding them in their natural habitats can be challenging. They usually inhabit aquatic and semiaquatic habitats, but in the case of Forcipomyia the larvae are terrestrial and prefer to feed on moist detritus and organic matter under bark or in moss. In some species they feed on algae.

This stick insect is staring at me with tired eyes. I wonder if it is aware of the two hitchhikers it is carrying?

With so many aspects of their life history still unknown, and especially due to their ecological and economical importance, you would expect to see more active research on Forcipomyia. The bad news is that there is not enough research going on. A few years ago, I approached Dr. Stephen Marshall, a dipterologist from University of Guelph, and suggested doing a PhD study about Forcipomyia’s biology, phylogenetics, and their relationships with their hosts. I was politely refused, unfortunately. I still believe there is potential for a cool project involving Forcipomyia, maybe someone will pursue it in the future.

A Moment of Creativity: Unwanted Neighbours

It has been a while since I started photographing for Meet Your Neighbours global biodiversity photography project, and throughout the years I have assembled a collection of some fantastic beasts (along with the information where to find them). But early on I had the idea of creating another collection of photos, a spinoff to the original MYN concept, bringing together neighbours that we often do not want to meet, or the way I refer to them: Unwanted Neighbours.

Human flea (pulex irritans). Central Coastal Plain, Israel

Unwanted Neighbours include household pests, biting and blood-sucking arthropods, disease vectors, venomous animals, parasites, and the like. Most of the photos can be found in my original MYN gallery, and it is only natural that this new collection will be smaller in size. Nevertheless it can be used as a reference for animals with any negative significance to humans, whether it is medical or economical. For example, brown recluse spiders are known for their potency, but are often misidentified. There are very helpful initiatives out there to help and fight the misinformation, like Recluse or Not. I decided that detailed high-quality photos of the spiders can help clarify doubts about their physical appearance.

Brown recluse spider (Loxosceles sp.), dorsal view

Black widow spiders also suffer the same public treatment as brown recluses, for no good reason. Sure, they are venomous, but they do not tend to bite unless they have to, even if you poke them.

Mediterranean black widow spider (Latrodectus tredecimguttatus) from Israel. Widow spiders are shy and usually keep to themselves.

Western black widow spider (Latrodectus hesperus)

This is not a gallery of “bad” animals. Despite their bad reputation, it is important to mention that there is no such thing as “bad” in nature. Many of these species are not even out to get us (excluding blood-feeders and parasites). Every creature has its rightful place on this planet. I was carful not to include just about any species that possesses venom, or incidental biters. Many times a bad interaction with an animal is our own fault. I am trying to avoid pointing fingers and propagating hatred towards nature, because in most cases these animals are doing exactly what they are supposed to, and we are just in their way. For this reason the representation of household pests, like ants, termites, wasps, and cockroaches will be kept to the minimum.

Everyone’s favorite nightmare parasite – the human botfly (Dermatobia hominis). Although unpleasant, in reality they are not so bad.

Telson and stinger of black fat–tailed scorpion (Androctonus bicolor). Scorpions will always try to avoid an encounter with a human.

At this point in time the Unwanted Neighbours page is still being constructed, but I expect it to stay relatively small in size. This is because most critters out there are harmless to us, and even those that have the potential to harm us, usually don’t. It is all about impact significance.

The Plot Thickens: One unlucky earwig

(or why you should not get attached to whatever you encounter in the wild)

Isn’t being outdoors the greatest thing in the world? Surrounded by the soothing beauty of nature, while observing species living together in harmony? It is easy to lose sense of reality sometimes. But things are not always what they seem, and this serenity is often deceiving. We do not like to think about it, but nature is a harsh environment. There is a constant struggle for survival, many animal and plant species compete with each other over resources and breeding space. In fact, many of the animals we humans encounter in the wild are already on their way out of the game, either due to senescence, diseases, pathogens or parasites. I always try to remind myself that if I stumble upon an elusive animal active beyond its normal activity time, and it is not startled by my presence, then something fishy is going on here.

That being said, I admit that many times my sound judgment is clouded by the sheer excitement of finding something I have never seen before. Case in point: During one of my visits to Mindo cloud forest in Ecuador, I came across a beautiful specimen of earwig.

Giant earwig (Allostethus sp.). Mindo, Ecuador

In general, earwigs suffer from a bad reputation, or lack thereof. While many people simply ignore them because they do not find them interesting, others find them terrifying due to their menacing-looking pincers. Nevertheless, these animals are both fascinating and harmless. First, they have interesting behaviors. Pairs often construct a breeding chamber together, and females display maternal care, tending the eggs and baby earwigs until they can fend for themselves.

Giant earwig (Allostethus sp.) guarding the entrance to its burrow. Breeding pairs of earwigs construct such chambers, where the female later cares for the brood. Amazon Basin, Ecuador

Second, earwigs cannot cause any injury to us. They cannot bite, and they possess no stinger or venom. Some species have an unpleasant odor, but you should not go sniffing animals that sport a pair of pincers anyway… Earwigs are omnivorous, and although they mainly feed on plant matter, they often use their modified cerci (the pincers) to manipulate soft prey such as moths and insect larvae. Earwigs are usually seen crawling on the ground or on plants, clumsily dragging their elongated body. However, they are also good fliers – underneath those square leathery forewings are neatly folded flight wings. During flight they spread like a delicate fan.

Detail of earwig wing. Ontario, Canada

The earwig I found in Mindo belonged to the genus Allostethus (family Labiduridae). It is a beautiful animal, with a length of up to 35mm, a shiny black body and orange legs, and each of its forewings is decorated with a bright orange patch. I found it active on a mossy tree trunk in broad daylight, something I should have regarded to as suspicious, as earwigs are nocturnal insects. In any case, I did not give it much thought and collected the specimen, hoping I could later get some behavioral shots of it preying.

Giant earwig (Allostethus sp.), what a magnificent beast!

However, I waited too long. In the evening the animal stopped moving and appeared dead. I was devastated. It still looked healthy, no signs of injury, starvation, or poisoning. I decided to keep it in the vial and moved on to other work. The next morning I had my first evidence of the culprit – the earwig started to grow some whitish “fur”.

Giant earwig (Allostethus sp.) covered with entomophagic fungus. What a magnificent beast?

This was not, of course, fur per se, but small filaments indicating an infection by a parasitic fungus specifically feeding on insects. Parasitic entomophagic fungi (such as Cordyceps and Ophiocordyceps) are extremely common in the tropics. Moreover, they are so diverse that many of their species are host-specific. In other words, a certain fungus species attacks only arthropods from a specific order or family. Typically, the growing fungus inside the still-living arthropod alters its normal behavior, causing it to roam in unusual locations, and often outside of its normal range of activity hours. In many cases the infected animal climbs on nearby tree trunks, branches, or positions itself on the underside of a leaf. This is done to allow better spread of spores from the fungus fruit bodies.

Detail of the fungus feeding on the earwig

Seeing that stunning earwig giving in and dying was heartbreaking, but it is important to remember it happens every day in nature. When walking in a tropical forest, there are signs of death by entomophagic fungi all over the place. It is hard to avoid corpses of ants, grasshoppers, moths, and beetles, all with bright fungal horns and tubers sticking out of their bodies. However, it is extremely hard to predict if a living arthropod is already infected with the fungus or not. Many times I have seen insects that behaved like “zombies”, only to later find out that they were harboring a parasitoid wasp or a parasitic worm. Looking for early signs of a fungus infection is trickier, but at least now I am a little bit wiser. I will know what to do the next time I see an earwig climbing up a tree at daytime.

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.

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 (Bufotes 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.

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 (Bufotes 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

Epomis dejeani guarding a recently captured European green toad (Bufotes 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.

Nailing that Megarhyssa shot – it’s all about flexibility

It is intriguing that I do not post much about North American insects. In fact, ever since I moved to Canada I became more and more obsessed with animals found in my home country (Israel). Some might say this is a common case of “you don’t know what you’ve got till it’s gone”, but this does not mean that North American insects are not exciting or interesting. On the contrary, there are many insect species I hope to see in person. One of these insects rewarded us with its presence during a day trip to Hilton Falls Conservation Area in Ontario. I thought I should write about it and share a little bit of the process of photographing it.

Giant ichneumon wasps (genus Megarhyssa) are some of the biggest North American wasps thanks to the females’ long (10cm) ovipositor, which is longer than the wasp’s own body. These wasps might look fierce but they are actually shy and harmless insects. They are parasitoids: their larvae develop as parasites living inside the body of other insects. The female’s ovipositor is therefore not a stinger, but an organ used to inject eggs into the larva’s host.

During our trip we came across an egg-laying female of Megarhyssa macrurus. I only had a couple of small lenses with me and no dedicated macro equipment, but still, I did not want to miss an opportunity to photograph a Megarhyssa during oviposition. I tried to go for a simple wide-angle macro style first:

Wide-angle photo of a female giant ichneumon wasp (Megarhyssa macrurus) during oviposition.

Very quickly I ran across one of the problems I mentioned in this post. The wasp is so thin and delicate and easily gets “lost” in the background, even when it is slightly out-of-focus. To get a better result, I started to cut broad leaves and placed them like tiles in the background. This photo was taken with the same, non-macro lens as above. Surprising result!

Female giant ichneumon wasp (Megarhyssa macrurus) drilling in wood to lay eggs

Megarhyssa wasps attack the larvae of another wasp, Pigeon horntail (Tremex columba), which bore into dead wood. The female can detect tiny vibrations coming from inside the wood by the feeding horntail larvae. She then proceeds to egg-laying: she bends her abdomen, exposing her ovipositor from its flexible sheath, and starts drilling. When she reaches a horntail larva, she sends an egg all the way down the ovipositor and injects it to the host. The parasitoid wasp larva feeds on the host and kills it, and then pupates inside the wood. The new generation of Megarhyssa wasps will emerge as adults in the following summer.

Back to the process of photographing – The next thing I wanted was to test the flexibility of the lens (I always recommend doing this), so I took a few more “creative” shots at different angles. What I like about this photo is that you can also see some of the previous holes this female drilled using her ovipositor.

Giant ichneumon wasp (Megarhyssa macrurus) injecting eggs into horntail wasp larvae found inside dead wood

The last goal was to get a dreamy background, showing some of the light entering through the canopy. This was a bit tricky, because the wasp was facing down towards the ground. Since I do not have special equipment (such as an angle-viewfinder or a tilt-screen), I had to be creative and improvise. Unknowingly, I had my photo taken while trying to compose the shot. I was completely unaware of my pose because I was too focused on photographing, and I guess some of the poses I tried might have been embarrassing for my trip partners… To tell the truth, I had no idea my body was even capable of getting into these positions. If you look closely, you can even see the wasp in this photo, it is very big!

Flexibility is important while photographing insects! Photo by Mio Konfedrat.

After much bending and neck-twisting I managed to get the shot that I wanted:

Female giant ichneumon wasp (Megarhyssa macrurus) in egg-laying

Nice to cross this incredible species off my “wanted” list.

Giving birth to a botfly

Sitting at my dentist chair for 40 minutes and suffering through the shrill sound of the ultrasonic cleaner, I suddenly started to feel contractions from my chest. Oh, no. Not now. Is it really happening? If it happens now this will be a visit I will never forget. Am I getting into labor?

2014 hit me hard in the face with all its goodies, that it was difficult for me to pinpoint the best moments. I still have one more story to share before I bid farewell and move on. For me, 2014 ended with a blast.

The story actually begins in fall 2013. Shortly after returning from BugShot Belize, I noticed that three mosquito bites on my chest were not going away. They became red, started to feel even itchier, and occasionally there was a slight pinprick sensation. I immediately suspected they harbored botfly larvae, and indeed confirmed this after a couple of days when the sensation became more intense.

Hypoderma bovis is a species of botfly that attacks cattle. The resemblance to a bumblebee is not incidental. Upper Galilee, Israel.

Botflies belong to the family Oestridae, whose larvae develop in the body of mammals as endoparasites. They are mostly known as pests of cattle, but also of rodents and other small mammals. At least one species, Dermatobia hominis, attacks primates and, as I learned the hard way, humans. And it does this in the most incredible way: the female botfly waits in ambush for a female mosquito to pass by, and when the blood-sucking insect shows up, a chase ensues between the two. The botfly grabs the mosquito in mid-air and takes her captive to the ground level, where she proceeds to do something unique to Dermatobia botflies – she starts to lay eggs under the abdomen of the now-immobilized mosquito. When she is done, she releases the mosquito from her grasp. Now the botfly has a carrier, a vessel to transport the eggs to a suitable host, preferably a mammal. Once the female mosquito locates a bloodmeal and lands in order to bite, the mammal’s body heat triggers the botfly eggs to hatch, and tiny larvae drop to the mammal’s skin. They quickly start to burrow into the skin, head in first. Some take advantage of existing pores, such as hair folicules or even the mosquito bite itself. The small larvae have several rings of curved hooks pointing backwards; these hooks assist in anchoring the larva inside the host’s tissue and prevent removal. After fully embedded into the mammal’s flesh, the larva (which is a foreign object) excites the body’s immune system, and feeds on the inflammation response and white blood cells that arrive to the area. Its only connection to the outer world is through the entrance hole, now called punctum, from which it extends its spiracles for breathing air.

This beautiful mosquito (Psorophora sp.) is known to be one of the vectors for D. hominis eggs. Photographed in Belize, in the same location where I got my botfly larvae.

When I first learned about Dermatobia hominis in Intro to Entomology course back in 2004, I could not help but wonder how it feels to have an insect living inside one’s body; whether it is painful; and does it show on the outside? Little did I know that I would become a host for the same species 10 years after. Well, it was painful indeed. Sharp, ticking pains that came and went in cycles. I immediately sought medical advice and came across a medical paper describing a method for removing botfly larvae using a suction pump. Fortunately for me, the leading author of the paper was a bus drive away. There was much excitement at the Tropical Diseases Clinic, when several doctors and medical students gathered to see my botflies. We removed three tiny larvae, and I was released home. Then, in the evening of the same day, I felt that sharp pain again from all three locations. Over the next days, the pain became worse, think of chest-stabbing, or corkscrewing in pulses with heated iron and you get the idea. There were larvae still in there. And it seemed they were growing faster because there was no competitor in there with them (the larvae we already removed). To make a long story short, I managed to remove one of these larvae (on Halloween Eve nonetheless!), accidentally killed another at the clinic (only to be removed later by me), and failed to remove the third one. It continued to remind me of its existence with pseudo heart attacks several times every night until it finally died and the punctum sealed over it.

This was quite the experience, and we even published a report of the case in a medical paper. Originally, I wanted to keep one of these larvae until completion of its development. As an Entomologist, I was eager to see the adult fly, let alone this might be the only chance I could give something in return after collecting and killing many insects for my scientific work. However, I was not lucky, and I started to accept the possibility that I will not get another botfly larva, surely not in such a convenient location again. And so, a year later I returned to Belize, not even considering the option that it might happen again. Remembering the lancinating pain that I experienced, I tried to be careful and well-protected from mosquitoes this time. So you can imagine my surprise after I returned home, when I found a new botfly larva in my chest, almost in the same location as last year!

At first I repeated the “routine” of visiting the Tropical Diseases Clinic, but the larva was still too small to be removed. Then I decided to leave the area as is and give the larva the space it needs. I was amazed to find out this larva was not even slightly painful. The feeling was completely different, I could easily feel it moving, but there was no discomfort about it. This is it. I am keeping it.
Maybe I should pause here and say that a botfly is probably the “friendliest” parasite one can wish for. It does not transmit any diseases, does not cause any significant damage to the body, does not leave any scars, keeps its area clean from infections by antibiotic secretions and most importantly – unlike other parasites, once it finishes doing its thing, it leaves on its own!

Portrait of human botfly (<em>Dermatobia hominis</em>) larva. The resemblance to a walrus is incidental.

Portrait of human botfly (Dermatobia hominis) larva. The resemblance to a walrus is incidental.

For more than two months I nurtured the larva, patiently observing while it was growing inside me. Photographing it was not easy, and essentially could only be done facing a mirror, but I learned the trick and eventually got used to operating the gear backwards. It allowed me to take this photo of the larva’s spiracles as it is breathing from the punctum (this might be graphic to some people, so you can view it here). But like I said my real goal was to see the adult fly, and I was restless in the final two weeks of the larval development in fear that I will miss the event. The botfly larva does not pupate inside the host. It first has to leave its host’s body, drops off to the ground and then quickly looks for a suitable place for pupation. In the end, the contractions I felt at the dentist were a false alarm, and I could not feel anything when the larva emerged eventually.

Human botfly (Dermatobia hominis) larva after emergence from its host, searching for a place to pupate.

Incubating the puparium has to be the hardest part in keeping a human botfly. In a fascinating paper from 1930, Lawrence H. Dunn describes how he deliberately allowed two botfly larvae enter his arm to document their development. Only later he found out that prior to his actions he was already infected with four additional larvae (on his other arm and leg). The paper is not an easy read, as it spans through the various sensations and types of pain the author experienced during this period. Eventually he had all his six larvae emerging as late third-instars, pupating and turning into adult flies. Unfortunately, this last part of the paper is poorly written and lack details. How moist was the pupation substrate and what was its composition? Did the larvae burrow or stayed on its surface? How long after emergence the adult flies started activity? And were there any losses during the pupation period? That last question is extremely important because I have heard of many failures in keeping Dermatobia hominis for the purpose of getting adults, and they mainly happened during the pupal stage. This is why I was so thrilled to find the adult fly one afternoon waiting in the container. What a great ending to 2014. And what a magnificent fly it is! Glowing red eyes, a pointy head with a bright silvery “face”, and the most dazzling blue abdomen, striking with metallic gloss. For me, this was literally the miracle of birth. No matter how I look at it, this fly is my own flesh and blood.

Human botfly (Dermatobia hominis) adult, fresh after emergence from its puparium (left)

Larva and adult of the human botfly (Dermatobia hominis). Hard to believe this is the same animal.

Totally worth it.

In this day and age, even a fly can take a selfie.

Was it worth it? Absolutely.

Piotr Naskrecki had his own personal experience bringing (two!) botflies to adulthood. You can read his blog post here. And do not miss the postscript!

UPDATE (12 Jan, 2015): Piotr has just posted a video about his botfly. Please go to his blog and watch it. I cannot recommend it enough; this is most likely the only filmed documentation that follows the botfly throughout its development to adulthood in a human host:
http://thesmallermajority.com/2015/01/12/dermatobia-redux/
Thank you everyone for the positive response to this story!

Entomologist and Photographer

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