Caterpillars, Part II

Okay, back to our regularly scheduled programming - caterpillars! To see the explanation for all of this caterpillar imagery, SEE THIS POST. I plan on posting one more series of cool cats later.

A Drab Prominent (Misogada unicolor) on the underside of a sycamore leaf (Platanus occidentalis). It is an extreme specialist, eating only the foliage of this tree. The caterpillar is also a midrib mimic, with its white dorsal stripe similar to the midrib of the underside of a sycamore leaf. When not feeding, the caterpillar typically rests with its body aligned exactly with the midrib, as this one is doing.

A Hickory Tussock (Lophocampa caryae) under attack from a nymph soldier bug. The predatory insect will jab the caterpillar with its elongated proboscis and essentially suck the life from it. Predation rates in most caterpillar species are extreme, approaching 99% in some cases. This is why female moths often lay hundreds of eggs. It is necessary in order to get some of offspring through the predatorial gauntlet and to the reproductive stage. But this is also why caterpillars are such a major underpinning of food webs. I did not intervene in this case.

One of the more bizarre North American caterpillars, the Monkey Slug (Phobetron pithecium). It is said to mimic the look of a shed tarantula skin. Why would an insect mimic that, when tarantulas do not occur in its range? But the genus Phobetron is largely tropical and occurs where tarantulas are commonplace. And many of the migratory songbirds that might eat a Monkey Slug winter in such tropical regions. This theory also presumes that shed tarantula skins are not tasty and avoided by birds. Which they probably are.

Slug caterpillars sort of ooze along the foliage, courtesy of their sucker-like feet. Here's a Monkey Slug feeding/enveloping a leaf edge, as seen from below.

I've said this before (and probably will again) but most caterpillars are specialists, eating only a small suite of plants with which they have successfully coevolved. This one, the Moonseed Moth (Plusiodonta compressipalpis - now that's a multisyllabic mouthful!), is a hyper-specialist. It only eats the foliage of the moonseed vine (Menispermum canadense). The caterpillar is a wonderful bird dropping mimic, not an uncommon ploy in the caterpillar world. Apparently, nothing likes to eat bird droppings. If you believe in reincarnation, come back as a bird dropping if you don't want to be eaten.

This is an Ochre Dagger (Acronicta morula), a real gem of a larva. It is an elm specialist and the botanically savvy might note that this specimen is on a black walnut. That's because we, as I recall, found this one on the ground. No one could remember its host plant, and I wanted a shot of it on a plant, the walnut was handy, and Voila! Yet another inaccuracy on the interwebs. But we're here to admire the Ochre Dagger's good looks anyway, not floriferous backdrops.

The caterpillar of the Pawpaw Sphinx moth (Dolba hyloeus) is larval art. The caterpillar far outshines the large sphinx moth that it becomes (if all goes well). Another extreme specialist that only eats its namesake plant, Asimina triloba (Pawpaw).

A Red-washed Prominent caterpillar (Oedemasia semirufescens) noshes on a fairly fresh oak leaf. This species is a master of vegetative camouflage and a consummate leaf-edge mimic. When ensconced on autumnal foliage dappled with brown, necrotic patches, it can be nearly impossible to see, even though it is a sizable caterpillar. A great spot by the incredibly sharp-eyed and knowledgeable Norah Tempus.

A Sigmoid Prominent (Clostera albosigma) snacks on bigtooth aspen (Populus grandidentatus). It is a specialist on plants on the Salicaceae family, and mostly aspens and cottonwoods, although it is said to eat willow (also in this family). This was another great spot by Norah Tempus, on about the only aspen to be found where we were. It was a new caterpillar for me, and probably everyone else who was with us.

The utterly bizarre slug caterpillar of the Skiff Moth (Prolimacodes badia). It looks like a gall on a leaf. John Howard and I have often speculated that the small white dot on the lateral ridge not far up from the tail (the rear of the caterpillar is at the right) may mimic the egg case of a tachinid fly. Perhaps a female tachinid on the hunt would see such a mark on a potential victim and decide it already had been parasitized. Tachinid flies are parasitoids that lay eggs on caterpillar hosts (and many other insects). The larva soon hatches and bores into the caterpillar and commences to eat it alive from within. By the time the larva is ready to emerge, it can fill nearly the entire body cavity of the host. Needless to say, the caterpillar does not survive such an attack.

However, taking the wind out of that theoretical egg mimicry sail is the fact that a real tachinid fly egg case is right next to the "mimic" mark (just below and left). The fake egg case clearly did not deter this fly. The air exchange hole created by the fly grub within is just left of the apex of the center of the Skiff cat's body.

A truly amazing slug caterpillar (it's hard to avoid all of the superlatives when describing caterpillars) is this, the Spiny Oak Slug (Euclea delphinii). This is one of the less colorful forms. Some of them are clad in bright pigments of yellow, lime, red and orange.

The epithet of the scientific name, delphinii, bears mention as it is almost certainly a misnomer. I'm assuming delphinii is a reference to Delphinium, the genus of larkspurs. I'm about sure this caterpillar does not nor would eat larkspurs - Spiny Oak Slugs eat various woody plants, trees, primarily. Delphinium stems from Delphinus, Greek for dolphin. But I cannot see how anyone would be reminded of a dolphin when looking at this caterpillar.