When is a caterpillar not a caterpillar?

Recently, my Google-fu saved me from making the second-stupidest mistake a lepidopterologist can make (the stupidest, obviously, is confusing a butterfly and a moth). While looking for caterpillars of the cabbage white butterfly (for science), my labmates and I found these guys nomming what turns out to be a species of loosestrife:Superficially, it looks a bit like a cabbage white, but it has no business eating that plant! (Why’d you think they call them cabbage whites?!) But it’s actually not even close. It’s the larva of a relative of bees, wasps, and ants—a sawfly, probably Monostegia abdominalis, which specializes on loosestrife*. How can one tell the difference? Count the prolegs – the leg-like stubs behind the “real” legs, which are the first three pairs behind its head. If there are seven or more, it’s a sawfly; if there are five or fewer, it’s a caterpillar (usually). The beast in the picture has eight pairs if you count the anal prolegs, the pair on the last segment.

While their larvae look quite similar, sawflies and butterflies/moths grow up to be quite different. Sawflies burrow underground to pupate, and the pupae tend to look like weirdly frozen adults, while lepidopteran pupae look like blobs, sometimes wrapped in silk, and usually, but by no means exclusively, attached to a branch or other aboveground surface. Adult sawflies look quite wasplike, and they get their names from the females’ sawlike ovipositors, which are literally used to saw into plants so they can lay their eggs inside them.

I noticed many of the sawfly larvae curled up tightly on leaves or on the ground, as in the picture below. (It’s also done quite a number on that leaf! And when I checked back a week later, the patch of loosestrife was completely skeletonized.) They seemed to do this as a defensive posture, with one staying curled up for at least five minutes after I poked it. This behaviour apparently isn’t unique to M. abdominalis, as evidenced by this adorable picture.

*Unfortunately, they only seem to eat Lysimachia species, not the evil, despicable, nefarious purple loosestrife, which belongs to a different family.

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More Hawaiian caterpillars: fiendish fly-killing ambush predators

Hyposmocoma is not the only unusual group of moth caterpillars I failed to observe in Hawai`i. Oh no precious, they are not.

Everyone knows what an inchworm looks like. Inchworms are the caterpillars of a family of moths called, appropriately, geometer moths. They tend to be well-camouflaged, resembling twigs. They eat plants, like most caterpillars, and some are serious agricultural pests.

A handful of Hawaiian species of the genus Eupithecia decided to break with tradition and become carnivores. They take advantage of their camouflage to fool unsuspecting insects into stepping on them. Then they suddenly reach back, grab the interloper with their talon-shaped legs, and eat it.

What’s especially cool is that they are not visual hunters. One species, in fact, hunts in the dark. Instead, they respond to touch: sensitive hairs on their backs tell them when prey is within striking distance. An insect walking on the caterpillar’s head or the front two thirds of its body will be unharmed.

It has been suggested, but not tested, that carnivorous Eupithecia‘s prey capture technique evolved from the “strike response” seen in some herbivorous caterpillars. The behaviour is best studied in the tobacco hornworm (Manduca sexta), the larva of a large sphinx moth. When something brushes against it, it reaches back and sometimes rasps its mouthparts against its skin. This behaviour could serve to startle birds that attempt to eat a hornworm, or to remove parasitoid wasps that would lay their eggs on it (and whose larvae would then eat the caterpillar alive).

By this point you should be dying of curiosity. You want to see these caterpillars in action, don’t you? Well fortunately, the BBC has delivered this nightmarish footage. And io9’s got your animated gif needs covered. Wicked, eh?

I’m going to end this post on a somber note, though. Carnivory by Hawaiian Eupithecia was discovered in the 1970s. The discoverer, Steven Montgomery, described a later foray to the site where he first found a caterpillar chewing on a fly. His report struck a chord with me, calling to mind my own impressions of the Hawaiian rainforest—and this paper is from 1983.

I recently returned to the volcanic cone on the Big Island where I first learned that Hawaii’s caterpillars were insect killers. After 10 years, I was keen to see if the endangered lobelia-like plants still found sanctuary in the steep cinder cone, because a carelessly set fire had destroyed the only other clump of these stately wonders. As I climbed the steep slope, I was stung on the head by a yellowjacket, a recently arrived pest that apparently stole into the Islands with cargo from the mainland. Rounding the top, I searched in vain for the lobelias. With them, half of the native forest plants had disappeared, and signs of rooting by pigs were frequent. Suddenly, a large European boar charged from under the koa tree and fled. I found no caterpillars that day, and heard few native birds. For this place, a conservation opportunity has passed, but on behalf of other Hawaiian forests, it teaches us what is at stake.

These species are not listed as endangered, but their habitat is dwindling; like many endemic Hawaiian species, their days may be numbered.

References
Montgomery, Steven L. (1983). Carnivorous caterpillars: the behavior, biogeography and conservation of Eupithecia (Lepidoptera: Geometridae) in the Hawaiian Islands GeoJournal, 7 (6), 549-556 DOI: 10.1007/BF00218529
van Griethuijsen LI, Banks KM, & Trimmer BA (2013). Spatial accuracy of a rapid defense behavior in caterpillars. Journal of Experimental Biology, 216 (Pt 3), 379-387 PMID: 23325858

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Case-spinning, aquatic, snail-eating caterpillars

Let me begin by admitting that when I worked in Hawai`i, I didn’t pay much attention to the tiny moths that I sometimes scared out of the moss. So this is a post about what I missed.

Hawai`i, being remote and geologically active, is famous for its endemic, explosive evolutionary radiations: a single founding population, finding itself far from both its natural food sources and its natural predators, diversifies into a flock of functionally diverse new species in a relatively short time. The honeycreepers, descended from a finchlike bird, are well-known for this; the Hawaiian picture-wing Drosophila flies are another oft-cited example.

There may be more species in the endemic Hawaiian moth genus Hyposmocoma than in the Hawaiian section of Drosophila, and I personally think these moths are way cooler. Consider the many decidedly non-mothlike things these guys do:

• The caterpillars make cases for themselves out of silk and bits of vegetation, pebbles, and other detritus. Silk-spinning is not unusual for a moth (viz. silkworms), but it’s usually reserved for building a coccoon to protect a pupa. Hyposmocoma caterpillars carry their silk homes on their backs much like a caddisfly larva. This fascinates me because caddisflies are the sister group to butterflies and moths. Is Hyposmocoma case-making an example of reversion to an ancestral state?
• The cases come in a wide variety of shapes—researchers studying them classify them into such categories as purse-, bugle-, cone-, and burrito-shaped. (Some of them look like oyster shells to me.) You can see some examples of these cases and of the adult moths here. Both moths and cases are quite pretty, but I expect they would be highly cryptic in their natural habitats.
• Four known species in the genus eat snails; they are the only lepidopterans to do so. I’ll let the researchers who discovered this behaviour describe it:

When [the caterpillars] encounter a resting snail of the native genus Tornatellides, they immediately begin to spin silk webbing attaching the snail shell to the leaf on which it rests, apparently to prevent the snail from sealing itself against the leaf or dropping to the ground once the larva attacks the soft tissue of the living snail. The larva then wedges its case next to or inside the snail shell and stretches much of its body out of its silk case, pursuing the retreating snail to the end of the shell from which there is no escape.

• Several species have amphibious caterpillars—that is, they can develop successfully either completely submerged in water or on dry land. While many insects, including caddisflies, dragonflies, and stoneflies, have aquatic young that become terrestrial adults, their young are obligately aquatic—they can’t develop out of water. The amphibious Hyposmocoma species are thus unique among insects. This ability has evolved several times independently within the genus. When underwater, the larvae can anchor themselves to the substrate with silk, preventing them from being swept away by strong currents. Scientists suggest that this amphibious lifestyle may be an adaptation to frequent floods in the rainforests in which these species live. Additionally, the limited diversity of insects with aquatic young in Hawai`i compared to such habitats on the mainland may have opened up a niche for these moths to occupy.

So let this be a lesson to me and to all of us who are focused on charismatic macrofauna that we should pay attention to invertebrates once in a while. You never know what they’re up to.

References

 
Rubinoff D, & Haines WP (2005). Web-spinning caterpillar stalks snails. Science (New York, N.Y.), 309 (5734) PMID: 16040699

Rubinoff D, & Schmitz P (2010). Multiple aquatic invasions by an endemic, terrestrial Hawaiian moth radiation. Proceedings of the National Academy of Sciences of the United States of America, 107 (13), 5903-6 PMID: 20308549

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Unusual heirlooms

My grandfather was a family doctor, and back in the day, it was totally cool for pharmaceutical companies to adverties their products willy-nilly. Perhaps the most interesting promotional material he received were these ads for the diet pill Lidepran (levophacetoperane) sent out in 1964. Each advertisement featured a pressed butterfly—the wings were real, with a cardboard cutout for the body—on a coloured background card. I presume the butterfly was meant to convey lightness/thinness and hence weight loss.

Oddly, although all the envelopes—there are 12 of them, each with a different butterfly and background—are stamped with “Lidepran”, about half of the cards actually advertise another drug, Largactil (chlorpromazine). Largactil is an antipsychotic made by the same company as Lidepran.

I’ve been able to find very little about this advertising campaign online. The only other source I’ve seen is this, which shows the envelope and inside of one of the cards (which I haven’t bothered to scan), and doesn’t indicate that any of them actually advertised Lidepran.

Interestingly, the scientific name of each butterfly was on each card, and they appear to be correctly identified at least to genus. They’re also from outside of North America. I wonder how they sourced these specimens, and whose idea the whole campaign was.

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Autumn colours III

Last week, before the edge of Hurricane Sandy abruptly made the weather miserable, there were a few warm, sunny days—a last chance to enjoy fall as the end of summer rather than the onset of winter. The trees were looking much less leafy; only the green understory and a few bright yellow mulberries still had foliage at all. But as the trees are stripped bare, you start to see things you missed before. Like bird nests, which now stand out starkly without leaves to hide them. This one, just barely low enough for me to take a picture of it, incorporates some bits of garbage into its woven rim.

Another sign of hidden life clings to a plant’s stem among the tall grasses at the edge of the forest. It’s a praying mantis egg case, which will hatch, if all goes well, next spring.

And finally, on a still-blooming aster, a spectacular yellow-green beetle. At first I thought it must be a yellow variant of the common spotted ladybug, Coleomegilla maculata, but a closer look at the pictures showed that the pattern of spots is different and that this beetle has long antennae, which ladybugs don’t. So I turned to my entomologist friends on Facebook, who came through with Diabrotica undecimpunctata, the spotted cucumber beetle. See how those top petals look like they’ve been gnawed down? The beetle probably did that. (‘Undecimpunctata’ means ‘eleven-spotted’, and if you zoom in you can indeed count eleven spots.)

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Today in unusual fossils…

Gratuitous extant collembolan picture.

Fossilized amber famously can preserve insects trapped in it. Sometimes we’re lucky enough to get a glimpse of a bug’s life from these specimens. One such fossil, found in a mine in the Dominican Republic, preserves a tiny springtail piggybacking on a larger fishfly (or mayfly, if you like). Springtails (subclass Collembola – close relatives of insects and teddy bears*) are wingless, but so small that they can easily disperse by hitching a ride on a larger insect. This individual was caught in the act, and in fact represents the first known case of such hitchiking (the technical term is phoresy) on a fishfly (order Ephemeroptera). Here’s part of the figure from the paper that described this fossil, showing the miniscule springtail clinging to the fishfly’s back. There’s also a video in the supplemental section of the paper showing a 3D reconstruction of the bugs.

Figure 1B from Penney et al. 2012: thorax of a fishfly with springtail on the upper edge, just left of where the wing attaches.

 

The second unusual fossil o’the day is one that it never occurred to me could be fossilized: a bird’s nest. And not just any bird’s nest: an ancient flamingo’s! The 18-million-year-old nest consists of leafy twigs and contains five eggs. It is thought that it was abandoned and sank to the bottom of the saline lake in which it was built before becoming fossilized. This sort of habitat is much like the ones flamingos inhabit today. The authors examined the eggshells microscopically to identify them as flamingo eggs, but, interestingly, the nest characteristics and egg number and size resemble those of grebes, the flamingo order’s closest living relatives.

So, two strange fossils that shed a bit of light on prehistoric animals’ behaviour. This is the sort of thing that makes me say “Yay science!”

 

Gratuitous flamingo picture. There are two species here – can you ID them?

*Not intended to be a factual statement.

References

Gerald Grellet-Tinner, Xabier Murelaga, Juan C. Larrasoaña, Luis F. Silveira, Maitane Olivares, Luis A. Ortega, Patrick W. Trimby, Ana Pascual (2012). The First Occurrence in the Fossil Record of an Aquatic Avian Twig-Nest with Phoenicopteriformes Eggs: Evolutionary Implications PLoS ONE, 7 (10) : 10.1371/journal.pone.0046972

David Penney, Andrew McNeil, David I. Green, Robert S. Bradley, James E. Jepson, Philip J. Withers, Richard F. Preziosi (2012). Ancient Ephemeroptera–Collembola Symbiosis Fossilized in Amber Predicts Contemporary Phoretic Associations PLoS ONE, 7 (10) : 10.1371/journal.pone.0047651

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Citizen science, both high- and low-tech

Two news stories that have warmed my heart in the past couple of weeks both involve non-scientists making important scientific discoveries. If you follow any biology blogs, you’ve probably heard about the new species of lacewing that was discovered on Flickr (here’s the paper describing it). Semachrysa jade was photographed by Gueg Hock Ping in Malaysia, and when entomologist Shaun Winterton saw the photo on Flickr, realized it was an undescribed species. Guek captured a specimen—necessary to confirm that the species was new—the following year. Along with Steve Brooks, another entomologist, they published the description in the open-access journal Zookeys. Interestingly, they found a second specimen of S. jade, already in a museum collection—one of perhaps millions of specimens that no one has yet realized represent new taxa.

The second story is a bit more old fashioned but exciting for a Mary Anning fan like me. The Keating family, while walking their dog, stumbled across a spectacular fossil on a rocky Nova Scotia beach. The beast is a juvenile sail-backed mammal-like reptile (maybe something like Dimetrodon) from the Carboniferous period (i.e. pre-dinosaurs). While this discovery is more low-tech than the lacewing from Flickr, what they both have in common is (1) someone with a keen eye getting out in nature and (2) the layperson connecting with scientists who can properly identify and document their find. In one case, a scientist reached out to the photographer, while in the other the family sought out experts when they found the fossil. Anyone could make the next cool biology headline.

So, in the words of Ms. Frizzle, get out there and explore!

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Look at this eldritch horror

She’s a stonefly (order Plecoptera), who came in to hang out on a loaf of bread one night at a friend’s house in the country. Note the bundle of eggs at the tip of her abdomen, which she’ll eventually deposit in water. The young are aquatic.

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dorky links feat. dinosaurs

Have I accumulated enough taxonomy-related links for another roundup? Am I too exhausted/lazy from field work to do any proper blogging? Yes and yes.

First, and most importantly, the NCSU Insect Museum has announced the winners of its awesome annual Hexapod Haiku contest. My favourite among the runners-up:

all the insects
I’ve killed–waiting
in the other world

The new species in this instalment are a UV-reflecting scorpion, a monstrous fossil that may or may not be called Godzillus, and a shockingly purple crab.

A short collection of goofy scientific names. I don’t understand why so few people want to do taxonomy. Think of the power you’d have, naming tiny primitive insects after Tolkien characters!

Random, related thought: describing a new species is like developing a DnD character. Except that you’ve lost your set of dice and your Player’s Handbook. (Actually, I think someone’s already indirectly made this parallel, viz. the Phylo, formerly Phylomon, card game.)

I’ve saved the best for last. This list of dinosaurs that “aren’t what they were” is frakking great. When I was just starting to be obsessed with dinosaurs, the idea that they were warm-blooded and related to birds was just becoming widely accepted. My childhood collection of dinosaur books was thus a mixture of those with illustrations of plodding stupid heavy-tailed brutes and those with lean and nimble, even graceful, beasts. But by the time I was in high school, things had changed even more: people had found fossil feathers. A lot of them. Now virtually every theropod (the predatory dinosaurs from which birds evolved), and even many non-theropods, is illustrated with at least a proto-feathery covering. The quill-like things on Psittacosaurus and Triceratops are pretty wicked. (A funny thing to note is that the Jurassic Park movies have always tended to be ahead of the mainstream idea of dinosaurs, first with the warm-bloodedness, then with the feathers and badass Spinosaurus.)

Okay, one more link, because the last one reminded me of it: T. rex trying, my favourite thing on the internet these days.

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First new species of 2012

(or at least the first to make headlines; I don’t actually pay that close attention)

The world’s smallest frogs—in fact, the world’s smallest vertebrates—are two newly described species from New Guinea, Paedophryne amauensis and P. swiftorum. What makes them particularly cool is that they are terrestrial, while the previous holders of the smallest vertebrate title were fish. It was thought that aquatic vertebrates could reach smaller size extremes because of buoyancy-related release from constraints. Apparently this is not so. Here’s the original article describing these two species and one of many media accounts.

Not a new species, but a new discovery about a known species: a Brazilian plant called Philcoxia minensis turns out to be carnivorous. It is unique in that it has underground leaves in addition to its normal leaves that capture and digest small nematode worms.

In cutesy scientific name news, just in time for the arrival of a certain baby of famous parents, entomologists named a species of horsefly Scaptia beyonceae, because its shiny golden abdomen is, as we like to say in the technical literature, “bootylicious”.

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