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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.

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.)

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

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

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

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.

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.

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 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

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

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!

 

Jumping spider mimicry in Brenthia moths

Many insects deploy mimicry to fool their predators into thinking they are highly defensive, venomous, or simply not to be messed with. A great fraction of mimicry cases involve adopting the appearance of ants, wasps, and spiders for these exact reasons. One of the most interesting cases, however, is predator mimicry: insects that take the appearance of their potential predators in order to expose them. I have already written about one such case in crambid moths, but in this post I want to present one of the classic examples for this mimicry in metalmark moths of the genus Brenthia.

At first glance, metalmark moths do not really resemble spiders. In my post about Petrophila moths I mentioned that observed spider mimicry might also be a case of pareidolia. In other words, we as humans seek familiar patterns surrounding us, so we recognize the image of a spider on the wings, but is it really mimicry? And indeed, after posting I was accused of having a strong imagination for thinking this is mimicry. There is a good point being made here – in the case of Petrophila there is a temporal barrier preventing the two from encountering each other under normal conditions. Petrophila moths are nocturnal while jumping spiders are diurnal. Nevertheless, the prevalence of such wing patterns in the insect world suggests that they have a role in the survival of those organisms.

Metalmark moth (Brenthia hexaselena) displaying its typical body posture, with wings raised like a peacock's tail.

Metalmark moth (Brenthia hexaselena) displaying its typical body posture, with wings raised like a peacock’s tail.

Brenthia moths are no different. It takes some imagination to strip them of their mothy characteristics to see the resemblance to jumping spiders. Members of family Choreutidae, the genus contains over 80 described species, all sharing the same appearance: a unique body posture, and wings patterns that are reminiscent of jumping spiders’ eyes. In fact their common name, metalmark moths, is due to the convincing “catchlight” area of the eyespots, often consisting of silvery scales. Brenthia species also move like jumping spiders, advancing by short bursts of movements while still retaining their wing display. Lastly, these moths are diurnal and can be seen active on top of leaves, just like salticid spiders. If you think it ends there for these moths in regards to anti-predator defenses, let me also add that their caterpillars deploy defense strategies as well. When alarmed, they launch themselves through holes chewed into the floor of their webbed feeding shelter, giving the term “teleporting through a wormhole” a new meaning.

Metalmark moth (Brenthia hexaselena) in frontal view, displaying wing patterns that resemble a jumping spider's face and legs.

Metalmark moth (Brenthia hexaselena) in frontal view, displaying wing patterns that resemble a jumping spider’s face and legs.

Brenthia moth (upper image) mimics jumping spiders (lower image) with wing markings, wing positioning, and posture. Figure from Rota and Wagner 2006 (drawing by Virginia Wagner).

Brenthia moth (upper image) mimics jumping spiders (lower image) with wing markings, wing positioning, and posture. Figure from Rota and Wagner 2006 (drawing by Virginia Wagner).

Portrait of a jumping spider (Phiale formosa). It is a little difficult to see the resemblance to the moth's wing patterns, but the important thing is that it works to the moth's benefit.

Portrait of a jumping spider (Phiale formosa). It is a little difficult to see the resemblance to the moth’s wing patterns, but the important thing is that it works to the moth’s benefit.

When discussing animals mimicking their predator, it is important to remember that we humans are not the target audience. This means that the imitator may not look too convincing in its mimicry to us, but still manages to trigger a desired response from said predator. However, when in doubt, the best way to know for sure is to put the suggested mimicry to the test through a series of experiments. Brenthia moths have become one of the best examples of spider-mimicking moths, thanks to rigorous testing. In their classic paper, Rota and Wagner placed the moths with their potential predators, jumping spiders of the species Phiale formosa, in arenas and recorded the outcome. They also used non-mimicking moths of the same size as control for the experiments. The results showed that the jumping spiders respond to Brenthia by displaying territorial behavior and waving their forelegs. In other words, upon noticing the Brenthia moths the spider predators immediately expose themselves. It comes as no surprise that Brenthia moths had a high survival rate in the experiments, as they could take off once the danger was revealed, avoiding predation. The control moths did not trigger a territorial response from the spiders and were preyed upon extensively.

Jumping spider (Phiale formosa) displaying territorial behavior in response to its own image. This is when the moth knows it is in danger.

Jumping spider (Phiale formosa) displaying territorial behavior in response to its own image. This is when the moth knows it is in danger.

One thing to keep in mind though is that this mimicry works well only because salticids are special among spiders. They do not make a web to capture prey, but instead rely on their excellent vision to detect prey. They are active predators, and therefore display a wide array of behaviors to communicate with other salticids. Jumping spiders will avoid other jumping spiders due to the risk of cannibalism. Brenthia moths take advantage of this behavior to get the higher ground by delaying the spider’s attack in order to escape. This makes them one of nature’s greatest con artists, but when survival is on the line, anything is kosher.

Papers mentioned in this post:

  • Rota, J, Wagner DL (2008) Wormholes, sensory nets and hypertrophied tactile setae: the extraordinary defence strategies of Brenthia caterpillars. Animal Behaviour 76(5): 1709-1713
  • Rota J, Wagner DL (2006) Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators. PLoS ONE 1(1): e45. https://doi.org/10.1371/journal.pone.0000045

Diaethria – a festive caterpillar with antlers!

In my last trip to the Amazon basin of Ecuador I had the fortune of meeting Paul Bertner, an acclaimed photographer and adventurer. I have been following his image posts and trip reports since I cannot remember when (and you should too!), and was excited to spend some time in the field with him, in hopes of learning some new tricks. It was great fun to discover hidden gems in the rainforest together, while discussing arthropod biology, conservation and photography.

During one of our night hikes we came across a tiny green caterpillar that was resting on a silky retreat on top of a leaf. At first glance it did not look very special, but then I noticed that its head featured two enormous antler-like horns. The horns were almost half the caterpillar’s body length! They were not simple straight horns, but rather complex structures that included many branches and hairs. I recognized the caterpillar as a member of tribe Biblidinae in the butterfly family Nymphalidae, but only later learned that it belongs to genus Diaethria.

Eighty-eight caterpillar (Diaethria sp.) with complex antler-like horns. Amazon Basin, Ecuador

Eighty-eight caterpillar (Diaethria sp.) with complex antler-like horns. Amazon Basin, Ecuador

Despite their small size, Diaethria butterflies are quite well-known thanks to the characteristic pattern on the underside of their hindwings. Circular bands in black and white surrounding black dots, giving the impression of the letters BB, Bd or the the numbers 88, 89, 69 etc’. The common names “88 butterfly” and “89 butterfly” are typically used for species in this genus. They are often seen puddling – an interesting behavior in which butterflies take up minerals from mud, sweat and feces.

Eighty-eight caterpillar (Diaethria sp.) is sometimes seen waving its horns while walking.

Eighty-eight caterpillar (Diaethria sp.) is sometimes seen waving its horns while walking.

Upon seeing the caterpillar I knew exactly how I want to photograph it. I wanted a frontal, head-on photo of the caterpillar’s head with the antlers stretched up in their full glory. What photo is more suitable for the holiday season than a festive caterpillar? Unfortunately, I did not have my high magnification MP-E lens with me (as mentioned, the caterpillar was tiny), so I gently collected it to photograph later. Let me tell you, photographing it was not an easy task. It seems that the caterpillar’s default behavior is to rest face down on the leaf, preventing any view of its antlers other than a dorsal one. It literally took hours to get it to change position, and I had to come up with a creative solution to get something remotely similar to the photo I had in mind.

This deer-mimicking caterpillar wishes you happy holidays and a happy new year!

This deer-mimicking caterpillar wishes you happy holidays and a happy new year!

One question that comes to mind is how do these caterpillars molt with such long head protrusions? Do the horns come out already stretched from the old head capsule or are they compressed as horn “buds” that inflate later? And what are those horns good for? They are most likely an adaptation against predators, but it is hard to say exactly how they are used. They can be used as defense to push away ants from attacking the caterpillar, or maybe the caterpillar drives away parasitoid wasps by waving the antlers from side to side. Hopefully someone will be able to document their function in the future and shed light on these remarkable structures.

 

This leaf got me thinking

I sometimes like to drift away in my thoughts and reflect on my days before becoming a biologist. It is amazing to realize how much I have learned over the years. This is something I think many people take for granted nowadays. We are flooded with easily accessible information on a daily basis. Try to think how many new things you learned just in the last month.
A little over a decade ago, I embarked on my first big overseas trip. Back then I knew close to nothing about Latin America. I had one goal in mind: to see poison dart frogs in the wild. Not too long into the trip I already felt victorious, after spotting some of these frogs in Bolivia and Ecuador. My quest took me to Costa Rica, where I found more of these stunning hopping jewels. Although I was mainly interested in amphibians, I was overwhelmed by the richness and diversity of arthropods. And more interestingly, despite my knowledge and exposure to various insect species, I realized how much I do not know and need to learn.

One such moment occurred when I visited the pastoral town of Monteverde, more specifically the butterfly gardens there. The guided tour I took passed near a moth wall, which was basically a white painted wall with a powerful light source pointing at it during nighttime. This was the first time I have ever seen a light trap. It was packed with hundreds of moth species. I was fascinated. The other visitors – not so much. They were pressing me to leave these “boring brown bugs” so we can head over to the butterflies area. “Just a second” I replied, “there is one moth I have to photograph”.

Leaf-mimicking moth, Monteverde, Costa Rica

Leaf-mimicking moth, from Monteverde, Costa Rica. Amazing camouflage, down to the level of leaf (=wing) damage and asymmetry. Image scanned from an old film slide.

“That’s not a moth” argued one of the visitors, “it’s just a fallen leaf that was blown onto the screen door”.
The local tour guide smiled but kept his silence.
“Well, if it is just a leaf…” I said and stood up, “…why don’t you touch it then?”
Upon being touched, the “leaf” immediately came into life and took off in a slow flight, disappearing into the foliage.

Many insects try to look like leaves. It is one of the most common types of crypsis. Only some of these insects, however, take it to the next level, mimicking not only the shape and color of leaves, but also their texture, tissue damage and even asymmetry. This moth had all of these. For years I have been waiting for an opportunity to photograph such a moth again, and finally, last year, I stumbled upon a similarly impressive species in the Amazon basin of Ecuador.

Leaf-mimicking saturniid moth (Homoeopteryx sumacensis), Amazon Basin, Ecuador

Leaf-mimicking saturniid moth (Homoeopteryx sumacensis) from the Amazon Basin, Ecuador. It was resting on the bathroom floor – I do not think I would be able to see it if it was resting among fallen leaves.

This species does look (and behave) very much like a leaf. Instead of laying flat like most moths, it holds its wings up in a way that creates a three-dimensional appearance. The forewing tips and margins are delicate; they are usually the first part to suffer tears and damage, contributing to the asymmetrical look of the false leaf. I knew immediately that I want to keep this photo for something special, and I decided to share it on the last day of National Moth Week. After posting it, the internet went wild. The photo was shared hundreds of times on social media, sparking discussions about evolution and moth diversity. It encouraged people to post their own photos of cryptic moths; others messaged me that the photo helped them to see the beauty and uniqueness of moths. I could not be happier.

Leaf-mimicking saturniid moth (Homoeopteryx sumacensis), Amazon Basin, Ecuador

From this angle it is easier to see that it is a moth. Leaf-mimicking saturniid moth (Homoeopteryx sumacensis)

It is important to remember though, that this moth is just one small example from a vast world of moths. There are over 150,000 species of moths worldwide, many undescribed, and many more waiting to be discovered. Moths are everywhere. There is more to them than meets the eye. They take many forms, and can sometimes make you doubt yourself. Until that moment in Costa Rica I was not aware these leaf moths existed, and even today I am not certain of their exact species ID*. Even nowadays within the highway of free information, I still have a lot to learn.

The positive feedback this photo received, as well as my orchid bees photo, made me realize also how much I am grateful for all the people who find my content interesting or inspiring. I never mention this, but it gives me a lot of energy. When things get rough, I remind myself that there is at least someone out there who thinks what I do is cool. I want to take this opportunity to thank all my followers, commenters and visitors. I got to know some fascinating people since I started posting. Thank you, everyone.

*UPDATE: This moth has been identified by Vazrick Nazari from the Canadian National Collections as Homoeopteryx sumacensis, a saturniid moth.

(Inter-)National Moth Week

When all that people talk about right now is going outdoors with their smartphones and tablets to play the current-trendy Pokémon Go, an augmented reality game of hunting fictional creatures, it seems appropriate to remind everyone that a similar “game” was already in existence centuries ago and still goes on today. It is called being a naturalist, and the rules are pretty simple – you just go out to search for, observe, and document everything that nature has to offer. I guess making people spend more time outside is a good thing nowadays, I just wish they were looking more around them instead of having their faces glued to mobile screens. Nevertheless, many players reported that while playing the game they stumbled upon “real life Pokémon”, in other words wild animals such as snakes, birds and even mammals. Several biologists on twitter decided to take a nice turn on this game and came up with the hashtags #PokeBlitz and #PokemonIRL, tagging and spreading facts about various wild animals, plants and fungi. It is a cool initiative that I hope will spread like fire, but in any case I wanted to use this opportunity to mention another similar event happening this month – National Moth Week.

Geometer moth (Rhodochlora brunneipalpis), Limón Province, Costa Rica

Green geometer moth (Rhodochlora brunneipalpis) from Limón Province, Costa Rica

National Moth Week is a citizen science project that sets out to increase public awareness and appreciation of moth biodiversity. It has been running continuously for 5 years, with the main event taking place on the full last week of July. During this week, moth enthusiasts set up light traps to attract moths and record the species found in their area. They are often joined by professional lepidopterists (scientists studying this insect order), who offer assistance in identifying moth species and wait for cool and unexpected discoveries. With the current accumulating evidence of dwindling insect populations, especially those of pollinators like Lepidoptera and Hymenoptera, this activity has huge importance. National Moth Week has become a global joint effort to record moth species, yet the project’s title remains “national” to emphasize the outreach activity on the local scale. Anyone can join and attract moths in the comfort of their own home, but many groups hold moth-watching events at public locations, attracting a large crowd of enthusiasts and curious people (you can attend an event close to you by searching in the event map).

Crambid moth (Desmia bajulalis), Mindo, Ecuador

Many Crambid moth species, like this Desmia bajulalis from Ecuador, have iridescent scales on their wings.

Setting up a light trap for moth watching is super easy. All you really need is a light source, and turning on the porch lights is probably the simplest way to attract moths. If you want to invest a little more, you can get a light bulb with some output in the UV range, as many moth species are attracted to this type of light. Many entomologists and insect enthusiasts use high-output mercury vapor bulbs because their spectral range seems to be more attractive for insects compared to other bulbs. Personally, I do not like these bulbs; they are very fragile, become extremely hot during operation and quite finicky to set up in remote locations. I use a compact version of a bulb that has a similar spectral distribution and get good results. My setup is built to be portable, so I now take my light trap almost anywhere I travel.

White witch moth (Thysania agrippina). Amazon Basin, Ecuador

Sometimes a light trap is not even needed for attracting moths. This gigantic white witch moth (Thysania agrippina) came to our bathroom lights in the Amazon rainforest, Ecuador.

light-trap

The light trap I used at Caves Branch, Belize, attracted a nice variety of interesting moths, including members of genus Petrophila (mentioned previously on this blog).

Moths attracted to light trap, Mindo, Ecuador

Moths (and other insects) gathering around a light trap in Ecuador

Moth feeding on top of another moth's wing, Mindo, Ecuador

When it gets crowded at the trap interesting behaviors can be observed, like this small moth feeding on a bigger moth’s hemolymph.

Finally, if you want to be able to record the species coming to your trap, you will need a surface for them to rest on. The simplest way to do this is by stretching a white sheet behind the light source. The flying moths will come to the trap, bump into the sheet and cling onto it, allowing close observation and photography. Not only moths, but also other arthropods can end up coming to the light trap as well. And, if you are lucky, even amphibians and reptiles can show up to take advantage of the abundant food.
The best thing about setting up light trap is that you never know what will show up. It is not uncommon to encounter a species that you do not know, or even better, find something that is very rare.

Geometer moth (Eutomopepla rogenhoferi), Mindo, Ecuador

Geometer moth (Eutomopepla rogenhoferi) from Mindo, Ecuador

Giant silk moth (Rhescyntis hippodamia). Amazon Basin, Ecuador

Giant silk moth (Rhescyntis hippodamia), one of the heaviest and largest moth species found in the Amazon Basin of Ecuador.

Geometer moth (Opisthoxia uncinata), Limón Province, Costa Rica

Geometer moth (Opisthoxia uncinata), from Limón Province, Costa Rica. This is probably one of the most common species in Latin America, it showed up in every light trap I have set up so far.

Wasp-mimicking moth (Gymnelia sp.), Mindo, Ecuador

Do not forget to check the surroundings of the light trap for even more species! This wasp-mimicking moth (<Gymnelia sp.) from Ecuador was found resting on the wall a few meters from the trap.

White geometer moth, Limón Province, Costa Rica

Some moths remind me of common butterflies. For example, this moth from Costa Rica somewhat looks like Small White (Pieris rapae)…

Giant silk moth (Titaea tamerlan). Amazon Basin, Ecuador

Giant silk moth (Titaea tamerlan) from the Amazon rainforest of Ecuador

Green moth (Epidelia sp.), Caves Branch, Cayo District, Belize

Green moth (Epidelia sp.) from Belize

Crambid moth silhouette, Mindo, Ecuador

Even a silhouette can be interesting! Crambid moth from Mindo, Ecuador.

Owlet moth (Sosxestra grata). Caves Branch, Cayo District, Belize

Sosxestra grata has become one of the most iconic Latin American owlet moth species, thanks to an excellent photograph taken by Thomas Shahan in BugShot Belize.

Crambid moth, Mindo, Ecuador

Some of the nicest wing patterns are found on the smallest species, like this delicate Crambid moth from Mindo, Ecuador.

So go out, and enjoy this fun activity. Moth-watching is the new birding. In fact, it might even be better than birding. It requires much less effort and preparations. In addition, the diversity of moth species found in a limited area can be astounding compared to that of birds. There is so much out there to discover, you really just have to look.

Petrophila: Salticid-mimic moths

A few months ago, I returned to Belize to conduct a small arachnid survey. While I was there, I took part in designing insect light traps for Caves Branch Jungle Lodge. The concept of a light trap is simple – flying nocturnal insects use the moonlight to navigate at night, and when there is a brighter light source present (like a light bulb) they are attracted to it. We wanted to have a few traps set up before the beginning of BugShot, and we ran a few trials in several locations using different lighting settings to see what works best and which insects show up at the traps. Very soon we realized that the traps attracted an impressive diversity of insects, but also their predators – spiders, frogs and bats quickly learned the locations of the traps and came regularly to feed. In several occasions fire ants showed up to raid the unsuspecting insects.

Petrophila sp. in typical resting posture, partially exposing the hindwings

Petrophila sp. in typical resting posture, partially exposing the hindwings

 

One of the insects that we saw in great numbers every night was a small, plain-looking moth from the family Crambidae. I would probably not pay attention to it if it were not for four black dots arranged in a row on the margin of each of its hindwings. Many moths rest with their hindwings concealed by the forewings, however these moths, belonging to genus Petrophila, had a unique body posture at rest, exposing only the dotted part of their hindwings. This pattern looked very familiar to me, but I could not pinpoint from where exactly. Then a few nights later one of these moths decided to rest pointing sideways with its head rather than upwards like most moths. And it finally hit me: this moth has an image of a jumping spider on its wings looking straight at you. The mimicry is so convincing that the moth wings even have hair-like scales where supposedly the spider’s head is.

Side view of Petrophila sp.

Side view of Petrophila sp.

 

I should be careful here. Pareidolia is a known phenomenon in which one searches for known patterns just about anywhere. It is what makes people see the face of Jesus Christ on a burnt piece of toast, it is what makes you see a face on a rocky terrain on Mars, and it what makes you see a number when looking at the wings of Diaethria species.
What I mean to say is that the color pattern on the wings of Petrophila species reminds me of a salticid spider, and perhaps it works the same for other animals as well. There is also a behavioral display that makes the mimicry even more deceiving: the moth moves its wings to mimic the movements of a jumping spider. In search for a second opinion, I turned to someone who breathes and sleeps jumping spiders. Thomas Shahan, who fortunately was around for BugShot, confirmed my suspicion and even came up with an ID for a possible model spider: a female Thiodina sp. And so we went on to find a jumping spider that looked like the one shown on the moths’ wings. In any case, to my untrained eyes it seems that this pattern is common in several moth genera, and in other insects as well. Some will debate whether this apparent image actually evolved to depict what we want it to be, but I can only imagine the reaction of a jumping spider to this image and behavior by the moth. Jumping spiders are known to have good vision; a jumping spider will stall to examine an opponent to avoid conflict. This may give the moth a few seconds to escape. A good analysis of similar mimicry in other species is discussed here.

A different species of Petrophila, recorded from the same light trap. This one is smaller and seems to have a slightly different spider image.

A different species of Petrophila, recorded from the same light trap. This one is smaller and seems to have a slightly different spider image.

 

The same Petrophila species as above, here with a possible salticid model - female Thiodina sp. from the same location in Belize. What I find amazing is that the wings even show some of the iridescence seen in the spider's eyes.

The same Petrophila species as above, here with a possible salticid model – female Thiodina sp. from the same location in Belize. What I find amazing is that the wings even show some of the iridescence seen in the spider’s eyes.

 

Petrophila moths are unique among Lepidoptera for having aquatic caterpillars. They occupy running freshwater habitats, rivers and streams, where they feed on algae by scraping the surface of submerged rocks and stones. The genus has a wide distribution across the Americas and many species occur in temperate zones in addition to tropical regions.

You know the moths are successful in their mimicry when you find others deploying the same strategy: Nectopsyche is a genus of caddisflies (order Trichoptera) that shows a similar pattern – moth-like adults have four tiny black spots arranged in a row at the margin of their forewings, along with pale stripes.

You know the moths are successful in their mimicry when you find others deploying the same strategy: Nectopsyche is a genus of caddisflies (order Trichoptera) that shows a similar pattern – moth-like adults have four tiny black spots arranged in a row at the margin of their forewings, along with pale stripes.

 

Not only moths, but also many other insects orders were represented in our trap catch. I hope that Caves Branch continues to make good use of these sturdy light traps to record the insects surrounding the lodge. There is great potential for scientific work to be done here.

Light trap in Caves Branch, Belize

Light trap in Caves Branch, Belize

 

Why sometimes it is important to remember small details from your childhood

One of the things I intend to write about every once in a while is the use of insects in art or popular culture. I am still not sure if these will be independent posts or inserts within other posts. I thought I would start by talking about keeping insects as pets or insects drawn in Japanese manga and anime, but this week while walking atop one of the hills at Otago Peninsula, New Zealand, I was inspired to write about something more personal.

When I was 10, I used to collect stamps. This hobby was largely encouraged by my grandfather, who was a serious stamp collector. I remember how just by looking in his albums at stamps from all over the world I sometimes imagined myself drifting away to a far away places. I could stare at them forever, and I also enjoyed the smell of old paper. Despite my grandfather attempts to infect me with his obsession, collecting any stamp from just about anywhere in the world was not very interesting for me. I decided to collect stamps of animals and plants only, but my favorite ones were insect-themed stamps, and I had many of them.
Among the first stamps I got were two that I found especially peculiar. They depicted butterflies and came from New Zealand. I remember them very well – they were probably very common because I had dozens of them. But the reason I was intrigued by them is because something about the butterflies looked a bit off. I knew that one of them looked like Vanessa atalanta in a way (I was able to read English at the time, but I did not know what a red admiral is), the wing pattern seemed wrong though, especially for the hind wings. And the art looked, well, a bit like cubism.

NZbutterflystamps

This week, over 20 years later, I got my answer.
While I was starting to make my way down hill, I caught a glimpse of some bright red color from a nearby gorse bush. I went closer, and the butterfly took off. Still, it did look like a red admiral during flight, and knowing the territorial nature of this species, I decided to wait. And lo and behold, a few seconds later the butterfly returned to the exact same spot, only this time it landed on a rock.

Vanessa gonerilla, New Zealand red admiral

Vanessa gonerilla, New Zealand red admiral

Vanessa atalanta, red admiral (photographed in Canada)

Vanessa atalanta, red admiral (photographed in Canada)

Now I could take a good look at it. Yes, definitely the same butterfly from the stamp, and the wing pattern fits perfectly. New Zealand red admiral, Vanessa gonerilla. Obviously this is a different species from V. atalanta that occurs in Europe and North America, but the similarity between the two species is striking, both in upper and lower sides of the wings.

Vanessa gonerilla, New Zealand red admiral

Vanessa gonerilla, New Zealand red admiral

Vanessa atalanta, red admiral (photographed in Israel)

Vanessa atalanta, red admiral (photographed in Israel)

While the upper side has the same type of contrasty combination of aposematic coloration – black, white and red (probably to deter predators), the lower side is an explosion of colors (especially in V. gonerilla), and is used mainly for camouflage.

Vanessa gonerilla, detail of lower side

Vanessa gonerilla, detail of lower side. Click for full size.

The red admirals belong to the butterfly family Nymphalidae, and it is a good opportunity to mention that members of this family look like they have four legs only (instead of six legs like all other insects. See photos above). But a close inspection reveals that the adult butterflies do have six legs. The forelegs are shortened and hairy, and held close to the body. They are used for cleaning the butterfly’s antennae from pollen and sometimes even for tasting nectar.

Portrait of Vanessa gonerilla, showing the specialized forelegs for cleaning antennae

Portrait of Vanessa gonerilla, showing the specialized forelegs for cleaning antennae. They also have hairy eyes, how cute!

By the way, similarly to the European and North American red admiral, the caterpillars of the New Zealand red admiral feed on nettle. The endemic nettle, Urtica ferox, also known as ongaonga, is a large stiff bush (can reach a few meters in height), covered with large stinging spines that remind me of the NYC skyline. I hear these plants are something you want to avoid at all cost, and they sound as bad as the nasty Urtica pilulifera I know from Israel. There was even one case of death caused by this plant (a similar event is reported here).

Urtica ferox (ongaonga). Insert: I see a row of Chrysler Buildings, I don't know about you.

Urtica ferox (ongaonga). Insert: I see a row of Chrysler Buildings, I don’t know about you.

By the way, I also got to see the tussock butterfly depicted in the second stamp during my first visit to Otago Peninsula a month ago. They were very abundant, flying slowly between the grasses. Unfortunately, by the time I arrived to the site the second time, they were all gone. It was nice to revive a piece of my childhood while visiting a foreign country many years later. Sometimes you have to go halfway around the world to come full circle.