Life on the Edge

In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment.

~Charles Darwin

Unicorn caterpillar wide view

Unicorn caterpillar positioning itself in a portion of the leaf it has eaten (click photos to enlarge)

I shared some images last week of one of my favorite moth larvae, the unicorn caterpillar. Their shape, coloration, and behavior allow them to blend in remarkably well with their environment. Turns out, they are not alone in their ability to hide in plain sight along the edges of leaves. It is a common strategy of many caterpillars, and I was delighted to find a few other species of leaf edge mimics in the yard over the past few days.

Wavy-lined heterocampa wide view

Wavy-lined heterocampa on hophornbeam leaf

One of the more remarkable leaf edge look-alikes is the wavy-lined heterocampa, Heterocampa biundata. It is variable in color, but frequently has brick red and white splotches along its sides that resemble necrotic leaf tissue. I assume this is a particularly effective camouflage for species that live during late summer and early autumn when many leaves are pock-marked by such splotches.

Wavy-lined heterocampa

Blending in to a hickory leaflet

This species is a generalist feeder on a variety of woody plants (I found them on two species of trees here in the yard). In addition to the leaf splotch patterns on their sides, they tend to align themselves along leaf edges in the areas of leaf they have devoured. The slight bump along their dorsal surface outline helps with this camouflage by making them look more like a leaf edge contour.

Chestnut Schizura on Viburnum nudum side view 1

It requires a careful look to pick these leaf edge mimics out of the background of green

Another excellent leaf mimic is the chestnut schizura, Schizura badia. I found a few feeding on the leaves of a possumhaw, Viburnum nudum. They tend to place themselves inside the outline of portions of a leaf they have consumed, once again making for a well-camouflaged caterpillar.

Chestnut Schizura on Viburnum nudum side view

A closer look

They also have brownish splotches that mimic dying leaf tissue.

Chestnut Schizura on Viburnum nudum

Dorsal view

This species is characterized by a diffuse yellow saddle over the dorsum of the abdomen and a large, irregular-shaped, brown patch on the sides.

Chestnut Schizura on viburnum leaf

A close relative of the unicorn caterpillar

It is a close relative of the unicorn caterpillar and also has the ability to shoot a blend of acids at would-be predators. The defensive spray comes from a thoracic neck gland and can be shot a distance of up to several inches.

Small-eyed sphinx caterpillar on cherry wide view

Small-eyed sphinx larva

Although not a leaf edge mimic per se, the other species I found yesterday does a good job of looking like a common leaf pattern on its host, wild cherry. I am pretty sure this is the first of its kind I have found in my years of caterpillar hunting. It is a small-eyed sphinx, Paonias myops.

Small-eyed sphinx caterpillar on cherry

The red splotches mimic leaf spots on wild cherry

The red splotches certainly are excellent mimics of the pattern on the underside of many wild cherry leaves this time of year. The behavior of this species helps with this deception  as it tends to stay underneath leaves (where the leaf splotches are most noticeable) during the day and then comes out to feed mostly at night. Wagner, in his excellent reference, Caterpillars of Eastern North America, wonders if the spots are more apt to occur on individuals feeding in the autumn, when cherry leaves tend to have more splotches. I continue to be amazed at the intricacies of nature found just outside our door. More on some other leaf edge larvae in my next post.

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