Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
Tony Eales from Brisbane sent us some lovely photos of arthopods, including some great examples of mimicry and camouflage (“crypsis”). Tony’s captions are indented.
Some mimicry and a few other random arthropods.
Three shots of a wraparound spider, Dolophones sp. These are small, only about 8mm across and fairly common, but rarely seen for obvious reasons. I find them mostly in the late afternoon as they start to build their web for the night. When building the web they just look like any other small orb-weaving spider, but when they see you approaching they scurry up a silk-line to the nearest twig and virtually disappear. As you can see in the third picture, when not all folded up in camouflage pose they display quite a bit of colour.
The ones I normally see have flattened dome-shaped abdomen but I knew there were ones out there with these weird turrets on their backs and had been wanting to photograph one for ages. Evolution is weird.
Next is a Hangingfly Harpobittacus sp. Hangingflies are in a separate order of insects Mercoptera along with Scorpionflies. We don’t have a lot of species diversity in this family in Australia but do have a lot of diversity at higher levels, with two families being endemic. Hangingflies are famous for their elaborate mating rituals in which the male captures prey to present to the females. I hope to observe this one day.
This female Clear-wing Persimmon Borer moth (Ichneumenoptera chrysophanes) is so far the find of the season for me. I have never seen such a striking wasp-mimicking moth.
The model is probably something like this Ichneumenon wasp Xanthopimpla sp.
And lastly just a little cutie. A very tiny Sandalodes sp. jumping spider with a tiny katydid nymph as prey. [JAC: Doesn’t it look excited?}
Here are two lovely photos of a mimic taken by photographer/biologist/naturalist Piotr Naskrecki in Gorongosa Park in Mozambique. These appeared on his Facebook page, and I asked for permission to reproduce them. I give his captions below. I’ve also turned this into a “spot the. . .” quiz for those who want a not-too-hard puzzle. The reveal is below the fold.
Piotr’s captions are indented.
Every now and then somebody posts a similar photo so, now is my turn. It is not a difficult one and you will get an extra point for naming the family of the subject. I ran across it today on the Cheringoma Plateau in Gorongosa.
Today’s photos, including a plant and many arthropods, come from regular contributor Tony Eales, who lives in Queensland. His notes are indented:
I’m sending a grab bag of some interesting things I’ve photographed lately.
When I was in Western Australia recently I found this beautiful sundew known as the Red-ink Sundew, Drosera erythrorhiza. I’m a big fan of carnivorous plants and this was a real beauty.
Another personal favourite is the spiders in the genus Arkys. I hope one day to photograph all of the known Australian species in this genus (around 18 in all) and back in March I got my sixth species, Arkys furcatus.
Another personal goal is to photograph at least one member of each insect order. This weekend I upped my count by two with a member of the Webspinner order Embioptera and a member of the Jumping Bristletail order Archaeognatha. [JAC: first and second photographs, respectively.]
On the weekend I also photographed my first Australian Funnel Web, a juvenile Hadronyche sp. While not the famous and deadly Sydney Funnel-web, I still wouldn’t want to be bitten: there’s very little info on the toxicity of other Funnelwebs and I don’t want to be the guinea pig.
Speaking of deadly arthropods I finally got a picture of Australia’s killer ant species, the infamous Jack Jumper Ant, Myrmecia pilosula. This is a large ant species (although they are middling for Myrmecia) at around 13mm for most workers. They are ferocious defenders of their nests with a very painful wasp-like sting and the ability to jump several inches. Before modern therapies, deaths from these ants occurred roughly once every four years, all due to anaphylactic shock.
I also recently found a member of the smallest species of Myrmecia in Australia, M. urens, a dainty little ant only about 8mm long.
Finally a weird case of mimicry. This is a Derbid planthopper in the genus Rhotana, known for having an image of a jumping spider on their wings.
Tony Eales, who provided this morning’s mushroom photos, called my attention to this paper in the Israel Journal of Entomology, describing a remarkable case of mimicry seen in a newly described species of salticid (jumping spider). Click on the screenshot below to see the paper, or you can download the pdf here. It’s remarkable because, at least as far as I know, it’s the first known case of a spider mimicking a caterpillar—and the mimicry seems quite good. There are cases of caterpillars apparently mimicking spiders, like the monkey slug caterpillar, but this is the reverse situation.
The authors, one of whom (Logunov) is at the Manchester Museum at the University of Manchester and the other a citizen scientist in Hong Kong who may have spotted the beast and recognized it as new, describe a jumping spider found in, of all places, Hong Kong. It was first spotted on a metal railing in Shek O Country Park (see photo 9 below showing it it on the railing), with the single known male kept alive for a few days for observation before being preserved and sent to Manchester. They speculate that another specimen in a different museum might be an immature female spider of the species, but don’t know for sure. The authors believe, though, that other individuals of the species might occur in tree canopies, as do other species in the genus Uroballus.
The species was named Uroballus carlei, and the story of its name is cute:
Etymology: The species is dedicated to Eric Carle (b. 1929), the American illustrator and author of more than 70 books for children and adults. His most renowned books include ‘The Very Hungry Caterpillar’, which chronicles the growth and metamorphosis of a caterpillar, and ‘The Very Busy Spider’. Indeed, these and other books by Eric Carle provide the first conscious contact of young readers with the natural world, being innovative tools for early-age environmental and biodiversity education.
It’s a fuzzy spider with a thin abdomen and covered with hairs: here are dorsal, ventral, and lateral views from the paper:
(from the paper): Figs 1–7: Somatic characters and copulatory organs of Uroballus carlei sp. n. (holotype ♂): (1) body, dorsal view; (2) ditto, lateral view; (3) ditto, ventral view. Scale bars for Figs 1–3 = 1 mm
The one putative conspecific female in a museum differs by having a “wide brown serrate longitudinal stripe on the dorsum” and shorter spinnerets, so the species is not markedly sexually dimorphic.
The nice part is that the authors noted “a striking resemblance of live specimens of U. carlei to a small-sized hairy caterpillar (below). This similarity was noted in 2016 in this species by another researcher, who didn’t name the spider as a new species but put it in the genus Uroballus. (One other putative caterpillar mimic seems to be the salticid U. koponeni from Malaysia, but pictures aren’t given.)
The notion that U. carlei is indeed a caterpillar mimic comes from three considerations. First, it looks like a moth caterpillar (Brunia antica; shown in photos 16 and 17 below) that is found in Southeast Asia, along with similar-looking “lichen moth caterpillars”, which eat lichens and are found in Hong Kong. In particular, the skinny appearance of the spider and its dense and protruding hairs making it look caterpillar-like (the hairs in the caterpillars are “urticating” or irritating to predators).
So the possible sympatry of the model (caterpillar) and mimic (spider) is point number two. For this kind of mimicry to take place (see below), both spider and caterpillar have to live in the same place—at least during the evolution of mimicry. Finally, observations of the spider kept alive in the lab showed that “the male moved rather slowly and often stopped”, erecting its anal tubercle while moving. This is not how most salticids move (they are quick and jerky), but it seems to resemble caterpillar movement.
Here is the putative model, U. carlei (8-15), and a member of the group of lichen moth caterpillars that it’s supposed to resemble (photos 16 and 17). It does look distinctly un-spider like, and, especially in photos 9, 12, and 13, caterpillar-like:
(from paper): Figs 8–17: General appearance of live male of Uroballus carlei n. sp. (holotype ♂; 8–15) and the caterpillars of Brunia antica (Walker, 1854) (16, 17). Scale bars = 1 mm.
So what kind of mimicry is this? It could involve three forms, all of which could have evolved roughly simultaneously.
Batesian mimicry. Because the model caterpillars sequester lichen toxins in their body and are supposed to be distasteful, and also have irritating hairs, the spider could have evolved a resemblance to a caterpillar that is already avoided by predators who have learned that it’s toxic and distasteful.
a.) In the first, the spider would, by resembling a caterpillar, get close to prey who haven’t evolved an evolutionary fear of these caterpillars. (After all, the caterpillars eat lichens, not insects.) Salticids, though, are carnivores, and could jump on unwitting insects like flies and beetles who approach them thinking they’re just caterpillars.
b.) The authors observe that caterpillars are “prone to attack by specialized parasitoids” who lay their eggs in the caterpillars and then the hatched parasitoids, like tiny wasps, can eat the caterpillar from the inside. It’s possible that these salticids could also attract these parasitoids because the spiders resemble caterpillars, and then, when the parasitoids come to lay eggs on them, the spiders grab them and eat them.
As the authors note, the mimicry hypothesis requires a lot more work—both in the field and the lab. Do predators who learn to avoid the caterpillars also avoid the salticids? Do parasitoids attack the salticids in the lab and then get eaten? And do insects that have experience with caterpillars, and learn not to fear them, then approach the spiders and get eaten? All this, of course, depends on finding more of these spiders, as well as some of the caterpillars they’re supposed to resemble.
Here’s a weird case of mimicry—or potential mimicry—involving an onycophoran and a caterpillar in Ecuador. It’s in American Entomologist, and is free (click on screenshot below, or see the pdf here).
First, in case you don’t know what an onycophoran is, it’s a group of 177 known species that occupy a single phylum, the Onycophora, which means “claw bearer.” Also called “velvet worms,” they are weird-looking, like worms with claw-bearing legs on a segmented body, big antennae and small eyes. They look like this:
And they have a bizarre behavior, described in the paper like this:
Although closely related to the arthropods, onychophorans are so unusual in their form, differing significantly from all other extant animals, that the taxon has been ranked at the level of phylum (Nielsen 2012, Grimaldi and Engel 2005). The Onychophora is unique due to the possession, by all species, of an elastohydrodynamic squirt-system in the mouth region. Remarkable structures, including glands that open on oral papillae, constitute a mechanism that enables onychophorans to squirt oscillating jets of proteinaceous liquid “slime” using slow muscular contraction (Concha et al. 2015). The slime rapidly fires from each papilla on either side of the mouth, intersects, and forms a disordered net (Morera-Brenes and Monge-Nájera 2010, Concha et al. 2015). The slime solidifies on contact with air and entangles small invertebrate animals; prey items or potential predators are quickly immobilized. Onychophorans then use their large-toothed, sclerotized jaws (Mayer et al. 2015a) to penetrate the victim, introduce saliva containing digestive enzymes, and partially digest the soft tissue prior to ingestion by sucking. Prey tissue may also be sliced up by the jaws and then swallowed (Lawrence 1953, Newlands and Ruhberg 1979, Hamer et al. 1997).
Here’s a National Geographic video showing an onycophoran sliming and then nomming a beetle:
Their appearance once made people think that onycophorans were a “missing link” (or rather something close to the common ancestor) between arthropods and annelids (segmented worms), and they were described as “living fossils”. But now they’re thought to be a sister group to arthropods + tardigrades, and not that closely related to annelids. Here’s their current phylogenetic position.
The new paper describes what may be a case of Batesian mimicy between a caterpillar and an onycophoran. The hypothesis is that a caterpillar which is tasty and preyed upon (birds, small mammals, reptiles, etc.) has evolved by natural selection to physically resemble an onycophoran, which is presumably avoided by predators because it has that nasty slime as well as teeth. If the predator has learned (or evolved) to avoid eating onycophorans, it may also avoid eating caterpillars who resemble them, thus giving a selective advantage to any caterpillar that closely resembles an onycophoran and thus can fool predators.
The authors found both onycophorans and caterpillars that resemble them in a collection of vegetation from trees in Ecuador (onycophorans are susceptible to desiccation and thus live in humid places in the tropics and wet subtropics). Here’s one of the tree-dwelling onycophorans and the presumably mimetic caterpillar. The paper’s caption is below, and be sure to watch the video at the link (I think they got “a” and “b” reversed in the figure caption, so I switched them).
Posterior view of the head of the caterpillar (B) found together with an onychophoran (A) in a sample of arboreal bryosphere. Note that the surface texture of the tubercles on the head of the caterpillar resembles the surface papillae of the onychophoran (see supplemental video 2 showing the entire caterpillar and onychophoran moving about in a lab set-up inside the field station).
A.
B.
That seems to be a pretty close resemblance, as the caterpillar has that pair of protruding bits that look like onycophoran antennae, as well as the body papillae that look like those on onycophorans. The caterpillars have no obvious defense that the authors could detect, and so they could be edible but avoided Batesian mimics of the onycophorans.
Now this is only a possible case of Batesian mimicry, though it looks suggestive to me. What we’d need to know to reach stronger conclusions is this information:
a. The caterpillar and onycophoran are attacked by a common species of predator (or more than one species of predator).
b. The predator has learned to avoid killing the onycophoran when it gets close to it, since the beast is nasty.
c. The predator will eat the caterpillar if it is “naive”, that is, if it hasn’t encountered an onycophoran and so hasn’t learned to avoid them. (This wouldn’t work if the aversion to onycophorans is evolved rather than learned.)
This could easily be tested in the lab (well maybe not that easily!). Just give a naive, hand-reared predator an onycophoran. See if it tries to kill it but then is repulsed and avoids them afterwards. At the same time, give other naive predators the caterpillars. They should be nommed readily. Then give a predator who has learned to avoid an onycophoran a “mimetic” caterpillar. If this is a case of mimicry based on predator learning, the predator should now avoid the caterpillar.
As it is, this is a suggestive but not well-documented case of mimicry, but it could be strengthened with some lab work.
Reader Mark Sturtevant has returned with a series of insect pictures that he sent on March 28. His notes are indented, and be sure to note the instances of mimicry and the weird mantidfly in the last two photos.
Here are some insect photos for WEIT. The first picture is a nice wood nymph butterfly (Cercyonis pegala). Various species are common in the local woods, but they are usually hard to approach. However, on this day it was overcast and somewhat chilly after a heavy rain, so this one was content to let me come in for pictures.
Next is a large mayfly that I had found on my car, so I transferred it to a nearby tree for pictures. It is one of the burrowing mayflies (Hexagenia), and is probably the most common species, H. limbata. As aquatic larvae, burrowing mayflies will get down out of sight into the silt and mud.
Everyone here should be fond of mimicry. One of my personal goals has been to find nymphs of a broad-headed bug since the nymphs are excellent ant mimics. Each species has a strong resemblance to a particular species of large ant, right down to very small details. So I was very happy to one day come across one such insect in a community garden, as shown in the next picture. This species looks to be in the genus Alydus, and I suspect it is mimicking the Eastern black carpenter ant—by far the most common large ant around here [Michigan]. Mimicking an ant is presumably done to avoid predation since ants taste very bad and not many things will eat them. Broad headed bugs are seed feeders, and they especially like to feed on seeds of legumes. So if I could find the preferred host of these critters I should be able to find more! This one was running fast through a strawberry patch (a feature of ant mimics is that they behave like ants), and so this heavily cropped picture is the only decent one that I have. The nymphs are good mimics, but the adults are rather ordinary looking as shown in this picture at another site.
A local nature center that strongly caters to school field trips recently built a native butterfly house, and I definitely wanted to visit that! The next two pictures shows one of the residents, which is the American lady butterfly (Vanessa virginiensis). This species is often mistaken for the more common painted lady (I had made that mistake as well!) So here is a handy key to tell the difference.
What do you suppose is the weird insect shown in the next picture? It took me a moment to figure out the order, and later on the family. This is a kind of wasp-mimicking longhorn beetle with very short front wings. The species is probably Necydalis mellita. I could only take two pictures before this nervous and alert insect took off.
I have a friend and colleague (we teach in the same department) who also very much enjoys doing insect macrophotography, and we often go out together to local parks. One thing that happens is that we compete a bit over who has the best ‘find’ for the day. My friend (Gary) wins this competition more often than not, but one day I saw a strange V-shaped thing sitting on a leaf. Could it be? Yes, it was a mantidfly!!! This one was a female, and we soon figured that there was little chance she would fly off since she was quite heavy with eggs. Mantidflies and praying mantises clearly show convergent evolution, but they are from completely different insect orders. Mantidflies are members of the order Neuroptera, and their familiar relatives include lacewings and antlions. The front limbs are usually held in the odd position seen here, cocked back farther than would be seen in a mantis, and they are not used for walking since they lack foot pads. This species (Climaciella brunnea) uses bright warning colors and a wasp-like shape to mimic a paper wasp. But the mimicry is a complete ruse since this predatory insect of course does not sting. We both agreed that this was “it” this time — the best find of the day.
Reader/biologist Jacques Hausser from Switzerland sends us another batch of lovely orthopterans (see here and here for parts I and II). Jacques’s notes are indented:
The third group of Orthopterans, the grasshoppers sensu stricto (suborder Caelifera) can be easily told apart from the Ensifera (bushcrickets/katydids and crickets) by their rather short and sturdy antennae and by the lack of a long ovipositor, replaced by four short chisels or burins allowing the female to bore a hole in the substrate to lay her eggs (Caelifera means “chisel bearer”). Their stridulatory and auditory equipment is also different: they stridulate by rubbing their hind legs against the elytrae, and their ears are located in the first abdominal segment. Grasshoppers are morphologically very homogenous (with exceptions!), and the coloration of most species is highly variable. The biblical locusts belong to this group.
Stenobothrus lineatus, the stripe-winged grasshopper, female. One can discern the dark eardrum just under the wing, to the right of the last green plate.
Mecostethus parapleurus, the leek grasshopper, male. This species likes reeds and other tall grasses in marshes and wet meadows. I don’t know what kind of relationship it has with leeks…
Chorthippus brunneus female, the common field grasshopper. It’s not obvious from this picture, but, like other mostly brown species, it prefers dry meadows with sparse vegetation.
Sphingonotus caerulans, the slender blue-winged grasshopper, and a well camouflaged one. The rear wings, hidden at rest, are pale blue (other related species have red hindwings), which makes it very visible in flight – but it instantly disappears when landing, fooling a would-be predator. Each time it moults, this spendid species can adapt its color to the environment – but it cannot change it between moults. It belongs to the subfamily of Locustinae together with the famous migratory locust.
Gomphocerippus rufus male, the rufous grasshopper, is easily recognizable by its black and white spatulate antennae. I call it the grasshoppers’ Pluto.
Same species, pairing. In grasshoppers the female is usually larger than the male.
Chrysochraon dispar, the large gold grasshopper. Like this one, females of several species are almost wingless, but the males keep fully developped wings, even if they are too short to fly—they need them to sing!
Another solution: they give up stridulating. Here is Miramella alpina, the green mountain grasshopper, a mountain species that replaces stridulation with grinding of the mandibles.
Acrida ungarica, the cone-headed grasshopper, a Mediterranean and East-European species. This is what happens to your head when the natural selection has decided that you should look like a bunch of twigs.
