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:
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:
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.
Aggressive mimicry. There could be two forms of this:
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.
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Logunov, D. V. and S. M. Obenauer. 2019. A new species of Uroballus Simon, 1902 (Araneae: Salticidae) from Hong Kong, a jumping spider that appears to mimic lichen moth caterpillar. Israel Journal of Entomology 49:1-9.
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I wonder if comic book writers will pick up on this.
I have an outline for a children’s book, “Carley, the Caterpillar Jumping Spider”, tell me if you know an artist who wants to try to draw it 😀
The mimics really get me. Amazing.
I’m thinking distasteful models is the more likely explanation. I don’t think most potential prey would get the “bird’s eye view” in which the mimicry is most convincing.
Yes, I agree.
Very amazing, and a fine example of the twists and turns that evolution can do.
I love the name. I read the very hungry caterpillar to our kids enough times that I can still pretty much quote it.
Very interesting spider too!
Jumping spiders are cool already. When you add fuzzy caterpillar mimicry to a jumping spider, that’s just beyond cool.
Presumably there’s no requirement that the mimic cross paths with the model species, since the selection pressure is mediated by the predator’s visual system.
That makes me wonder whether a migratory predator could exert selection pressure on prey species at one end of its migration to resemble noxious species at the other end, in which case mimic and model wouldn’t need to be sympatric.
Well, yes, they can live in different places if the “detector species” moves between those different places. I believe there are some coral snake mimics in places where coral snakes don’t live, which have been explained by migratory birds that learn (or evolve) the mimicry in one place and use their behavior to select for patterns in a different place. But I can’t remember where I heard that.
Photos are not convincing evidence. Before deciding, I would like to see a video showing how spiders and caterpillars move around in their natural habitat. I would also like to know if the caterpillars are common, of the same size as the spiders, and birds and lizards avoid the caterpillars and prey on spiders. Birds quickly learn to spot prey by cuing in on distinctive behavior that gives them away. An alternative hypothesis is that the Uroballus at rest and in ambush mode reap the advantage of camouflage by looking like a nondescript wad of inedible plant fluff.
I’m surprised so much new stuff continues to come out of China.
I do think that papers should include videos where applicable. This medium seems underused. Perhaps it’s just that people are used to reading physical copies.
-Ryan
There are many fields where having video rather than images would help but be hence impossible in the usual journal format.
Even something like algorithms can profit sometimes from showing how it works over time.
Nothing to see here, folks, it is the same object in all photos :-).
TEN comments on a science post? Maybe i should have written about the Royal Baby. . .
There’s really not much to say. It’s definitely an interesting species, but I doubt many of us are in a position to find it, since it’s so small.
-Ryan
We definitely appreciate your science posts though. It’s one of my favorite parts of the site.
-Ryan
If you write about an over privileged baby, that is a post I will skip. I skipped every article about it recently at every venue that tried to push those articles.
I like the science posts, but rarely comment on them. I learn, but do not know sufficient biology to relate some additional fact or opinion about e.g. mimicry.
Pretty much all I learned about mimicry has been from your books and website. Well, biology classes taught me there was such a thing but little else. That was not a major topic of my collegiate biology classes (two, I think).
I do enjoy science videos ever since Wild Kingdom. That was Mutual of Omaha, I believe.
You know, you can just tell me the articles you like and not which ones you skip (note the dismissive tone with which you describe these). It’s not helpful to me to hear what people don’t care to read, as I write about what I want. But thanks for your approbation of the science posts.
That is quite amazing. This makes my little exciting spider almost boring https://noelliesplace.com/2019/05/10/regal-jumping-spider/