Leading a Double Life on the Edge

There is more both of beauty and of raison d’etre in the works of nature- than in those of art.

~Aristotle (384 BC-322 BC)

The adaptations of insects in our yard are both beautiful and incredible. Here is a little more on some leaf edge caterpillars discovered the past few days…

Double-toothed prominent

Double-toothed prominent on elm leaf (click photos to enlarge)

One of the most exciting finds was a group of double-toothed prominent caterpillars (Nerice bidentata) on an elm sapling. These guys are amazing in that they have noticeable fleshy “teeth” on their dorsum that mimic the double serrated leaf edge of elm leaves, their host plant.

Double-toothed prominent early instar 1

Early instar of double-toothed prominent larva

Several of them molted over the past few days and I noticed what seems like a slight change in behavior between the different sizes. The smaller larvae are somewhat darker in color and seem to feed along the leaf edges in a more exposed position.

Double-toothed prominent on small leaf

Their color and pattern aids in the deception

The brown tips of the prolegs match brown spots along the mid-vein of the leaf.

Double-toothed prominent close up

Later instar

Larger larvae appear lighter in color, and seem to feed at an angle that puts them slightly under the leaf. The leaf underside is lighter in color than the top, so maybe this is why. The larvae also have angled stripes along their sides which mimic the venation of the leaves, adding to their effective disguise.

Double-lined prominent

Double-lined prominent on elm leaf

While looking at other elm saplings, I came across another species that seems to mimic both the leaf edge and the twigs of its host plant. When viewing the dorsal surface of a double-lined prominent (Lochmaeus bileneata), the reddish-brown color resembles an elm twig.

Double-lined prominent 1

The light stripes may mimic the leaf petiole

When viewed from the side, the white and yellow stripes along the cater[pillar’s body look like the mid-vein of a leaf, and the brown resembles dying leaf tissue.

Double-lined prominent 2

Even the head stripe helps in the disguise

The feeding position (head towards the tip of the leaf, body along the mid-vein) reinforces the effectiveness of the cryptic pattern and colors, with even the stripes on the head capsule resembling part of the angled leaf venation. I suppose it should come as no surprise that I can spend hours wandering around the yard, amazed by the small wonders all around me. I hope you all can spend some time outside this holiday weekend and discover wonders of your own.

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.

Blending In

When we see leaf-eating insects green, and bark-feeders mottled grey, the alpine ptarmigan white in winter, the red-grouse the colour of heather, and the black-grouse that of peaty earth, we must believe that these tints are of service to these birds and insects in preserving them from danger.

~Charles Darwin

Yesterday, while working in the yard, I stumbled across an unusual caterpillar just beneath the surface of my mulch pile. Two things about it jumped out at me – first, it was pretty large compared to most caterpillars so early in the year, and second, its colors were so striking. And then, to add another, when I picked it up, it jumped and thrashed from side to side.

Ilia Underwing larva on twig

Ilia Underwing larva (click photos to enlarge)

I remember seeing a picture of this species in my caterpillar bible (Caterpillars of Eastern North America, by David L. Wagner) but this was the first one I have encountered. After identifying it as an Ilia Underwing, Catocala ilia, I discovered it is actually one of the most common of the underwing moth species in the East. How have I missed seeing one all these years? Then I read that there is only one generation per year and mature caterpillars are most often seen in early spring. To be honest, over the years I admit to doing more of my caterpillar searches later in the season, when some of our more showy species reach their full size. Look what I have been missing! Sources say that the eggs are laid in the fall and hatch in early spring. The larvae feed primarily on oak leaves. Perhaps my find was burying down into the mulch getting ready to pupate.

Ilia Underwing larva showing rosy underside

Ilia Underwing larva showing a glimpse of the rosy underside

The dorsal surface can be gray or brown, or, as in this case, a mottled color that is a great mimic of a lichen-covered twig. One thing they have in common is a noticeable rosy color to their ventral surface (this guy did not like to be handled so here is just a glimpse of its rosy underside).

Ilia Underwing larva on lichen 2

Ilia Underwing larva blending with a lichen-covered branch

I brought the larva inside with a couple oi twigs I found laying nearby and photographed it. When I nudged it onto a twig, it would thrash, and then crawl a short distance and assume the position. When on a bare twig, it clings tightly but is visible (perhaps the gray or brownish larva blend in better on bare twigs). But when it crawled onto the lichen-covered branch, I could see how this caterpillar can literally disappear before your eyes (or perhaps those of a hungry bird).

Ilia Underwing larva on lichen close up

The color patterns and textures of this larva are a great lichen mimic

It is always a treat to discover something new and learn how it lives its life just outside my window…all I need to do is get outside and look to once again be in awe.

Chrysalis Camouflage

Cloudless Sulphur chrysalis

Cloudless Sulphur chrysalis shortly after caterpillar’s last molt (click photos to enlarge)

I blogged last week about the Cloudless Sulphur butterflies I have been seeing down east and in my Piedmont garden lately. I included the photo above of a fresh chrysalis. I have only seen one other chrysalis of this species and it was much more colorful, but the field guides said their color can be quite variable so I didn’t give it much thought. The caterpillar had been placed in a mesh cage just before pupating as it had stopped feeding and was crawling off the cut plant I had brought it in on, sure signs that it was getting ready to transform. And, as they often do, the caterpillar had again crawled off the plant material I had provided in the cage and pupated under the edge of the lid of the container, making for a less than ideal photo backdrop, and requiring me to pin some black felt behind it for the photographs.

Cloudless Sulphur chrysalis after it dries

Cloudless Sulphur chrysalis a few days later

I checked on it again a couple of days later and was amazed at the color change, much more like the one I had found a few years ago in a patch of host plants down east. The colors are beautiful – a faint pink, tinged with yellow highlights, and the whole thing being a odd obliquely stretched form suspended by a silken girdle. The color change should not have surprised me as I have seen several species which undergo a shape and color change in the chrysalis within a short time after they form. There is usually some adaptive advantage for even unusual forms and colors in nature but I was initially at a loss as to how this odd combination might serve the pupa.

Partridge Pea flower after blooming 1

Partridge Pea flower after blooming

So, I went back out to the power line this morning and looked at the plants. The explanation may lie in the fading blossoms. As the bright yellow flowers fade, they droop, and when viewed from the side have a shape similar to the chrysalis.

Partridge Pea flower as it fades

Partridge Pea flower as it fades

They also start changing color to an orange-yellow, and then, gradually, to a somewhat pinkish-yellow hue. The lines on the chrysalis may mimic the sepals and folds in the fading flower petals as well. I also noticed a few pinkish leaves of other nearby plants as they begin to turn color for the onset of autumn. Online, I found images of a chrysalis from this species that was light green and the lines resembled the veins of a leaf. Perhaps this species can have a chrysalis that is variable depending on the surrounding plants. Whatever the case, it is certainly one of the more unusual and beautiful chrysalises I have found.

Dressed for Success

And what’s a butterfly? At best, He’s but a caterpillar, drest.      John Grey

And there is one species of caterpillar that dresses better than any other – the Camouflaged Looper, Synchlora aerata. This is the unusual larva of the Wavy-lined Emerald Moth (okay, the quote isn’t quite right in this case…).

Camouflage Looper

Can you see the caterpillar?

Every time I am out in the garden I always take a few moments to just look around for interesting critters. As I watched a few pollinators on the Blazing Star (Liatris sp.) yesterday, I noticed something move. But there was nothing there…then it moved again, and I knew what it was – a Camouflaged Looper. This caterpillar has the unusual habit of disguising itself by cutting plant parts from the flowers on which it is feeding and sticking them onto its dorsal surface. The larvae feed on a wide variety of plants although I have most often found them on Blazing Star, Black-eyed Susan, and a few other yellow composite flowers.

Camouflage Looper 3

Camouflage Looper and its “costume”

In a 1979 article in The Journal of the Lepidopterists’ Society, Dr. Miklos Treiber, of the University of North Carolina, wrote about the camouflage abilities of these inchworms. The larvae cut off flower parts, seeds, and even entire flowers, and attach them to needle-like projections on their upper body surface. In a series of experiments he removed their floral covering and they immediately  began to replace the camouflage.

Camouflage Looper on yellow flower 1

Camouflaged Looper on yellow composite

Furthermore, when moved from one flower type to another (purple to yellow in his case) the larvae began to replace their old camouflage with flower fragments from the new plant.

Camouflage Looper 4

Camouflaged Looper on Blazing Star

He also noted that the fragments are passed through the mouth of the larva before being attached and that a mucilaginous substance (aka “caterpillar spit”) was secreted by the larva onto the fragments. He speculated that this substance seems to play a role in maintaining the freshness in these fragments. The caterpillars also maintain the effectiveness of the covering by replacing withered floral parts with fresh ones.

Camouflage Looper 5

Camouflaged Looper looks like plant debris when not on matching flower

Dr. Treibe hypothesized that this looper’s ability to change disguises allows it to have a much more varied diet than some other caterpillars because it isn’t restricted to eating only those flowers or plant parts that it resembles in appearance. And I noticed that even when it is moving between flowers and is on a stem, leaf or other background, the caterpillar simply looks like some plant debris rather than a potentially tasty meal for any passing bird.