Shedding Light on the Subject

The insect world is nature`s most astonishing phenomenon. Nothing is impossible to it; the most improbable things occur there.

~Rachel Carson

Last week we were looking for caterpillars for this past weekends’ BugFest event, and ended up making a couple of nocturnal excursions (it is often easier to see cryptic caterpillars at night by the light of a flashlight or UV flashlight). One location had a mix of meadows and forest along a gravel road. As I scanned the edge, a bright spot caught my eye.

Cloudles sulphur resting under a leaf after dark

Cloudless sulfur butterfly resting under a leaf after dark (click photos to enlarge)

It was a cloudless sulfur butterfly perched under a sweet gum leaf for the night. I don’t often get a chance to see roosting butterflies, so this was a treat. The flash didn’t seem to bother it, but it did illuminate something else just to the side of the sleeping sulfur.

Katydid molting ventral view

From this angle, it was hard to tell what it was (can you?)…

At first glance, all I could tell was that some insect was molting, but it was very odd-looking from the ventral side.

Katydid molting

Another view and it looked like some sort of katydid in the process of shedding

I moved to get a better view of the side of the insect and guessed it to be some sort of katydid caught in the act of shedding its exoskeleton. Arthropods must shed their hardened exterior “skin” in order to grow, a process we call molting, or ecdysis. The process is initiated by hormones and involves growing a new cuticle under the old one, then increasing the internal pressure, so that the outer skin splits. The katydid then pulls itself out head first, and hangs underneath until the new skin hardens. These insects undergo what is known as incomplete metamorphosis that progresses from egg to nymph to adult. The young stages resemble the adults, but usually have incomplete wings, and often disproportionate body parts relative to the final stage. Butterflies, in contrast, undergo complete metamorphosis with 4 stages – egg, larva, pupa, adult. Molting is both a necessary and a hazardous process – necessary in order to grow and mature; hazardous in that things can go wrong. Molting takes time, and the insect is very vulnerable during this process due to its inactivity and softened cuticle. This is why many insects tend to molt at night or early in the morning, when there is less chance of being seen by potential predators. I stumbled upon this one shedding at about 8:51 p.m. I took a couple of images and continued on our caterpillar quest. I returned via the same path and stopped to check on the katydids’ progress.

Katydid molting 1

It had pulled all the way out of the old skin by 9:32 p.m.

About 40 minutes had passed, and the katydid was all the way out of its old skin, but still had a ways to go to harden its new exoskeleton and change into its adult color. I did see that is is a female with a long sword-like egg-laying appendage (ovipositor) protruding out its back end. This looks like the final molt based on the ovipositor and the size of the new wings. By the looks of it, I am guessing this whole procedure may take a few hours before the katydid is ready to resume normal activities. I wished her well, and we headed back to the car, a few caterpillars in hand, and a memory of another astonishing phenomenon of the insect world.

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