As the days are getting cooler here in Northwest Arkansas, birds are beginning to migrate from their regular summer haunts to the consistent warmth of the tropics, squirrels are poised and ready to start stashing the season's mast, some of the leaves are starting to blush, and butterflies and moths are giving it one last go at mating and laying eggs. Many species are already done for the year, but many others are flying fresh to get a final round of caterpillars raised. These caterpillars are the only hope for a species' survival through a cold winter. They are the last frontier. This last crop will spend the winter buried in the leaf litter on the forest floor as pupae and sometimes as adults. Occasionally, a butterfly can be seen on a warm day in the dead of winter. One of the notorious species for jumping the gun is this Question Mark. I've seen these in just about every frigid month you could name.
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| Question Mark (Polygonia interrogationis) |
These and their brethren found during the first few days of spring will either be crisp or tattered. The crisp individuals are most likely those that overwintered as a pupa, while those that are tattered probably overwintered as adults.
As I've mentioned before, I really enjoy butterflies (and the more conspicuous moths), but enjoying their caterpillars is another level deeper; a level which I'm, of course, guilty of crossing into. The connectedness of it all is amazing, which I will get into more later. First, let's enjoy some caterpillars. A personal favorite is this Spicebush Swallowtail caterpillar. Not uncommon, but definitely unusual.
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| Spicebush Swallowtail. This is the last stage before pupation. The younger caterpillars look like bird poop. |
This species, like most others, have specific "host plants" that they are adapted to eat. In the case of the Spicebush, it is either spicebush or sassafras. I've seen them most often on sassafras where they fold a leaf in half and use it as a shelter. As you can probably imagine, any bird poking around on this tree would get quite a scare when it peeked inside and saw this snake mimic. It's amazing that not only has each species adapted to their own set of food plants (there is some overlap), but also adapted for protection since caterpillars are such tasty treats for a variety of wildlife. Here you have your typical camouflage, but incredible none-the-less!
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| Clover Looper Moth Caterpillar (Caenurgina crassiuscula) |
The looper moth family (Geometridae), of which the caterpillar above is a member, has really mastered camouflage. The Camouflaged Looper
(Synchlora aerata) takes things a step further by attaching plant parts to itself from whatever it is feeding on; usually these are colorful flower petal pieces. The loopers also encompass what many would call "inchworms", though this Clover Looper was more like a 3" worm...
As with the Spicebush Swallowtail caterpillar, many young butterfly larval stages are bird poop mimics, but the Viceroy caterpillar is really good at it all the way through its later stages.
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| Viceroy Caterpillar (Limenitis archippus) |
Of course, it doesn't fool us when viewed at such close range. While the larvae get by as feces, the adult is a Monarch mimic, threatening birds with the bad taste of milkweed which is one of Mother Nature's great lies since the Viceroy caterpillar uses willow as its host plant.
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| Pandorus Sphinx (Eumorpha pandorus) |
While the inconspicuous stick to camouflage, some of the braver species go with gaudy. Take this Pandorus Sphinx for example. This was a species I had always wanted to see. My wish came true recently! Most adult butterflies are equally as interesting as the caterpillars, unfortunately the same cannot be said for moths. The caterpillars are usually far more interesting than the adults; the sphinx moth (or hawk moth) family is an exception though. The adults are more like hummingbirds than anything and can often be found nectaring on flowers at night.
And, if you're going to go gaudy, why not make it yet another species that mimics a Monarch in some way. In doing so, you are protected since nobody wants to eat something that feeds on nasty-tasting milkweed. This is the case of the Clouded Crimson Moth caterpillar below, a species that lives in an open, prairie environment where Monarch cats could also be found.
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| Clouded Crimson Moth Caterpillar (Schinia gaurae) |
Sometimes methods used to skirt around gaudy aren't enough for a caterpillar. Many species, namely dagger moths and tussock moths have developed spines and hairs, some of which can sting and others that are just plain annoying. Not even a bird wants to eat a hairy caterpillar, though some species get around that by whacking a cat on a branch to knock off spines and hair before eating it! Some of these can pack a nasty sting even to humans. This Smeared Dagger Moth caterpillar (Smartweed Caterpillar) is a prime example; fancy yet dangerous.
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| Smeared Dagger Moth Cat (Acronicta oblinita) |
Birds are not the only predators for caterpillars, but maybe the most obvious. Caterpillars are highly parasitized by certain wasps and flies. Both of which will lay their eggs on a caterpillar. The larvae will grow up and feed on the caterpillar, eventually killing it. There you have it, yet another protective step taken by adding an armor of spines and hairs. The White-marked Tussock Moth caterpillar even goes so far as to have tufts of hair that make it look like it's already been parasitized! Being one who is definitely tuned into nature, I can't help but wonder why the so called "Seven Wonders of the World" are all man-made.
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| White-marked Tussock Moth Caterpillar (Orgyia leucostigma). Amazed yet? There's more! |
It's not always about protection from predators, though. Amazingly, some species of caterpillars have formed mutualistic relationships with other insects. Namely the Lycaenids (hairstreaks, coppers, and blues). Remember? My favorite family. According to David Wagner's
Caterpillars of Eastern North America, over half of the 5,500 known species in the family are tended by ants as caterpillars. "Tended by ants" can mean a variety of different things. In many of the cases, the caterpillar secretes a sugary liquid that the ants love. In providing for them, the ants offer up undying protection. Some species will eat the ant larvae, but are kept around as a food source for the ants during hard times. According to Eastwood & King (1998), in the case of a hairstreak butterfly in Australia
(Arhopala wildei), it feeds on a species of tree tended by some very aggressive ants
(Oecophylla smaragdina) who like the sweet sap it produces. The ants viciously protect the tree, yet somehow the caterpillars survive. How does this work? Well, there's another species of ant
(Polyrhachis queenslandica) living on the same tree that shuts itself away in protected shelters during the day to keep from getting killed by the vicious species. The caterpillars live in these "compounds" with the ants and are carried...yes, carried...out to feed at night when the aggressive species is not active. The benefit provided to the ants is, again, a sugary secretion
. On the other side of this story, in the same tree, the aggressive Oecophylla ant has its own Lycaenid caterpillar that it tends. This species, (Liphrya brassolis) feeds on the ants, while the ants gain nothing due to the caterpillars' extremely thick skin. This is a pretty deep, extreme example, but absolutely amazing! In some cases, the caterpillars have adapted a sort of language (vibrations) that can call on their ant buddies when in need. Here's one of our simpler North American examples. An ant tending a Gray Hairstreak caterpillar, waiting for that sweet secretion.
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| Gray Hairstreak Caterpillar (Strymon melinus) |
Gray Hairstreaks are fairly general as food preferences go. This individual was on yellow ironweed
(Verbesina alternifolia). None of our butterflies in the family Lycaenidae are very big, but most are fairly conspicuous. Their young, however, are small and inconspicuous; almost slug-like. This one blended in very well and it probably would've slipped under my radar had it not been for the ant.
I bet you didn't think CATERPILLARS could be so interesting, so I hope I've managed to blow your mind. They're not always easy to find, but once in the right mindset they seem to pop out everywhere. Almost any plant you can think of will be on the list of some species of butterfly/moth as its food plant...that makes things pretty easy.
In every walk with nature one receives more than he seeks.--John Muir
I must say, Muir was right. I always receive more than I seek in the outdoors. And now you, dear reader, have received a heck of a lot more than you sought by simply reading this post.
Enjoy!
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