Archive for the ‘Biology’ Category

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:sawfly larvaSuperficially, 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.sawfly larva 2

*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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Since it’s going to be a cold day tomorrow, and since I’m already feeling a little nostalgic for Hawai`i, I dug through my pictures to find these images of moths! I have no idea what kind they are. They could be invasives for all I know. Aren’t they pretty though?

I wish I knew how to identify moths.

I wish I knew how to identify moths.

I could totally see this being a Hyposmocoma, but who knows?

I could totally see this being a Hyposmocoma, but who knows?


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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.

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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On overcast nights in Chicago, the sky is orange with light pollution. A few nights ago, the snow-covered roof of the gym was as orange as the clouds above it, but for the dozens of crows huddled in rows formed by the roof tiles, like sheet music lain on its side at the end of rehearsal.

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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.


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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Friday morning, before the weather warmed up and the rain started, there was fog in the air and a foot of snow on the ground. On the lakefront, you could turn your back on the freeway and see only the ice-covered beach to one side, dark bare branches to the other, and, just barely, the silhouette of a jetty across the frozen bay. The nearer shore, built up with limestone blocks, was encased in eerie bluegrey icicles like a row of ghostly fangs. These dripped onto jagged, jumbled slabs of ice that bordered a dark and uninviting ring of slushy water—inhospitable except for the sewage pipe outlet, where a couple of mallards huddled.

The lake beyond this was a flat expanse of white all the way to the distant point where the ice blurred into the fog. But right in front of me, right in the middle of the little bay, was a black spot on the ice. A falcon—was it a falcon, or a hawk? Does it matter?—was tearing at a carcass, alone on the frozen lake. The gulls flying above seemed to give it a wide berth. A swath of feathers, and maybe blood too, but all colour had drained from this winter landscape, dusted the ice in an arc around the solitary bird; a few of them began to dance away from shore on the wind. The falcon, unruffled, focused on its prey.

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Let me warn you, readers, that the following is a rant brought on by a meeting with my advisor, and that I’m well aware that I’m probably repeating what other scientists have been saying for years. Still, let me say it.

The scramble for limited resources (both funding and places in prestigious journals, not to mention tenure-track jobs), while encouraging innovation, also discourages thorough comparative studies, cataloguing of natural history, and replication.

In Heliconius butterflies, for example, there’s a glut of work on finding the genes involved in speciation, especially those that control wing colour pattern and mating preferences for said patterns. It’s increasingly hard (according to my advisor) to convince reviewers—whether for grants or for publications—that simply looking at the same genes in yet another Heliconius species is novel enough to warrant money/a place in a prestigious journal.

And yet, these studies are exactly what we need. It would be fantastic to have a suite of speciation genes identified in every Heliconius species; the comparisons we could make would be useful and perhaps more generalizable than just a handful of studies on a small fraction of the genus’ members. Think of how we could test hypotheses about speciation with such a dataset! We could look for a snowball effect with a sample size of more than three! We could figure out how often the same genes are involved in different speciation events, and how often hybridization promotes or prevents speciation! Yet amassing that much data would take up several PhDs’ worth of effort, and once a minimum threshold of species is reached, the research program ceases to be novel, and therefore becomes non-competitive. It’s also work that requires too much effort for a side project (assuming you ever want to graduate) or to hand off to an undergraduate minion. So it doesn’t get done.

Oh, and if you want to try replicating some else’s study, the way the scientific method allegedly works? Definitely not novel. This is also a problem. (Seriously, read this paper if you have access to it. Every scientist should read it.) Or if you want to pursue as a side project some outstanding question on your study organism’s behaviour in the wild? That’s extremely labour-intensive, and not likely to get you a “good” publication. But these sorts of studies can lead to important innovations.* Not always, maybe not even often, but eventually.

If I had my way, I’d try churning out as many of these uninteresting/redundant studies as possible. I don’t particularly want to be a brilliant scientist, just a competent though mediocre** one. But given the current PhD to academic job opening ratio, mediocrity doesn’t cut it.

*In fact, we argue in a similar vein when governments try to divert resources from basic research to applied (I’m looking at you, Harper Government): we can’t predict what basic research program will eventually lead to important innovations.

**Sometimes this word does not have a negative connotation!

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