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.

KatyDid, But Wishes She Hadn’t

It provides strength to the armor plate of the beetle, keenness to the lancet of the mosquito, endurance to the rasping fiddle and bow of the cricket and the katydid.

~Edwin Way Teale, on the properties of chitin

Late summer and early fall are a time of abundance of many types of invertebrates in our woods. Many are reaching their maximum size and activity levels in preparation for however they spend the winter (most as eggs or pupae).

Katydid

A species of katydid out in the yard (click photos to enlarge)

Last week, I noticed a particularly large katydid on a shrub in the front yard. The songs of katydids reverberate through the treetops here most of the summer, but the onset of cooler weather has quieted them somewhat. They make their sounds by stridulation – rubbing one body part against another. In the case of katydids, they rub the base of the front edge of one forewing against a bumpy ridge at the base of the opposite wing.

eardrum katydid

Eardrum on front leg of katydid

Other katydids hear these sounds by means of oval-shaped tympana, or eardrums, located on each front leg.

Katydid from above

Katydid from above

There are several species of katydids in our area and I have not yet learned how to accurately identify most. I think this one may be one of the Angle-wing species, perhaps the Greater Angle-wing Katydid, Microcentrum rhombifolium, but I can’t swear by it. Looking from above, I can see why this group might be called Angle-wings.

Katydid wing

Katydid wings are great leaf mimics

And it is the wings that draw your attention to these beautiful insects once you are lucky enough to find them. The wings help make these katydids excellent leaf mimics, which comes in handy when you spend most of your time feeding on tree leaves.

Katydid wing close up

Detail of katydid wing showing venation

The closer you look, the more amazing the detail becomes. While looking for caterpillars this time of year, I have been surprised on many occasions to suddenly come face to face with a pair of katydid eyes staring back at me when I grab a tree branch. This disguise can be quite effective, an important trait when you represent a large tasty meal to many other forest-dwellers from birds to mice to predatory insects and spiders. But, blending in isn’t always effective, especially when you take flight, or simply fall from your feeding perch.

Spider woth katydid 1

Katydid caught in spider web outside my window

This is especially true around houses, where katydids are often attracted to lights at night. And, unfortunately for them and many other night-flying species (and the unwary person exiting a doorway), a variety of spiders also seem to like the windows and doors of woodland houses as sites for their large sticky webs. One night last week, a large katydid was entangled in the web of an orb weaver spider just outside the kitchen door. Too bad for her that KatyDid what she did in this case.