Of all the wonderful butterflies and moths that I have seen in my short (but somewhat eventful) life, the only other insect that can perhaps compare with these winged beauties in terms of sheer wonder and elaboration in evolutionary design, are perhaps their very own offspring: the caterpillars. Now it is quite understandable that most people would find this statement perplexing as it is true that the general rule is for caterpillars to remain as unnoticeable as possible! A caterpillar, generally speaking, is literally nothing more than a skin filled with hydro-static hemolymph and developing organs! Consequently, it is really quite fragile and vulnerable to attack! Staying hidden, or properly camouflaged with one's surroundings, is therefore a pretty necessary strategy that most caterpillars have to learn, or die trying! Some caterpillars, however, have absolutely no need to hide! And while a caterpillar is most certainly not the most aggressive of animals, many of them have developed chemicals means through which they may defend themselves from predators and they often do this in very fashionably beautiful and amusing ways!
The caterpillar of the puss moth (Cerura vinula) is a fairly unremarkable caterpillar for most of the time. That is, until you piss it off! It really is about as aggressive as a caterpillar can be. When threatened, the caterpillar will rear up on its hind legs to display a striking looking "face" that might startle predators into backing off. To enhance the illusion, the caterpillar also possesses a pair of tentacles or tendrils at the back of its body that it can wave about furiously and menacingly to ward off potential predators. If all else fails, though, the caterpillar will employ its final method of defense: a concentrated spray of formic acid to the face! Formic acid is a type of poison that is typically produced by ants, wasps, and bees, and the caterpillar of the puss moth is quite unique in its ability to do so.
Not all caterpillars have to be aggressive to ward off predators though, and in fact, aside from the larvae of the Puss moth, few actually are! Most caterpillars employ a more passive aggressive means of defense typically meaning they will remain passive even when a predator is being aggressive. But who needs to be aggressive really, when your entire body is covered in a cornucopia of envenomed spikes that will make even Lady Gaga turn green with envy! Slug moth caterpillars (Limacodidae) are perhaps one of the most interesting caterpillars in the lepidopteran world! The variation in coloring and form is only as diverse as the various means through which they defend themselves. Many though, are covered in some form of urticaria. This means that brushing against one of these caterpillars can be potentially discomforting or even painful! Caterpillars of the tussock moth also advertise themselves brazenly with tufts of fur and setea that look more at place in a Mardi Gras parade than on an insect. The caterpillar, however (surprisingly enough) is not poisonous per-say. Rather these setea break off very easily and may cause a rash if embedded in the mucousa membranes of animals. This sort of defense is believed to target the mouths and eyes of predators as the thickness of the fur, and the extreme ease through which they break off is often enough to protect the insect from the predator's initial strike.
As "prevention is always better than aggression" seems to be the prevailing policy when it concerns most insects, many of these caterpillars are also brightly colored so that they will not easily be missed such as the caterpillar of the lacewing butterflies (Cethosia sp.) While one might think that this would attract predators, the bright colourations are typical of aposematic warnings in the animal Kingdom. Basically they advertise: "Attack me, and you might just regret it!" Many animals learn to avoid caterpillars with such coloring and are therefore less likely to attack them even by accident as the bright colors force the predators to take special attention to their presence.
Because the methods of aposematic coloration are so good at warding off predators, this has led to the emergence of several "copy cats" in the animal kingdom. After all, why waste time and energy synthesizing poisons from the plants that you eat when you can just "look" poisonous and be done with it. The hickory horned devil (Citheronia regalis) is a perfect example of this. These caterpillars look extremely BADASS! In fact in terms of appearances, these caterpillars are like the siege tanks of the insect kingdom. The caterpillar is one of the largest in North America and can grow to over 5 inches in length and are crowned with brightly colored, cruel looking spines along their heads and down their backs. The caterpillars themselves, however, are quite harmless and it would seem that evolution is finally catching up to them! Despite their fearsome appearances, more and more of these caterpillars are consumed by birds every year and the numbers are increasing! In fact in some areas they have even been recorded to have become "local bird favorites". Better keep up with the evolution, guys!
However when all is said and done, perhaps the best defense IS still a best defense and why expend any energy at all synthesizing poisons, drawing attention to oneself, or pretending to be something one is not when one can simply just blend into one's surroundings? Some caterpillars, however, take "blending in" to new extremes. The caterpillars of the jewel moths (Acraga sp.) are named not for their adult form (which resemble furry dog-moth hybrids) but rather, their larval stages which literally resemble translucent/transparent mounds of gelatinous flesh! These caterpillars theoretically remain entirely invisible by refracting and reflecting the colors and lights from their surroundings making them, quite literally, mother nature's cloaking device! Perhaps the "prettiest" way of remaining unseen.