…comes the newest in reality based, sustainable living instructional programming: Corruption Construction!
In a previous post I wrote a bit about the Warty Leaf Beetle (Neochlamisus gibbosus), a member of the Cryptocephalinae subfamily. Fascinating due to the fact that the adult form seems to be a perfect mimic of caterpillar frass, this species is much more interesting than I had imagined.
This species is highly, if not solely, associated with blackberry as a host plant. While watching these guys and looking for other insects on these plants I kept noticing gall-like structures, usually on the undersides of the leaves.
Paying closer attention, I noticed that these structures were not galls, nor were they attached directly to the plant tissue – they moved. On closer inspection, I could sometimes see the legs of the creature that resided within the house.
I had to crack one open to see if I could get an idea of what sort of organism built and resided within. As you can see in the photograph below, the animal appeared to be a beetle larvae.
It took me a while to put it together, but eventually I confirmed that the larvae belonged to the same species as the adult beetles that I observed all over the blackberries. My next question was, on what materials did the larvae use to build its shelter? Usually, an insect will use detritus or perhaps fresh plant tissue that it processes to make a protective enclosure like this. These guys do it a bit differently.
It starts with mom. As she oviposits, she encases each egg with a layer of her own feces and some rectal secretions. As the larvae hatches and grows, it continues to expand its home by building with its own feces to accommodate its increasing bulk. Here is a photo of an adult and larvae close together.
The mimicry that insects exhibit can be astounding. Walking around Shaw Nature Reserve this summer, I noticed quite a fresh and disgusting looking bird dropping on a small bush near the trail. Something made me take a closer glance and I discovered it wasn’t a poop at all, but a caterpillar. The caterpillar was an early instar of the Giant Swallowtail Butterfly (Family Papilionidae). These caterpillars feed on member of the citrus family, the Rutacea, and this individual was found on a small hop bush. Youngsters like this one will most often be found directly on the surface of a leaf (as poops are most likely to be found), while older stages are likely to be found on leaf petioles or slender branches. In citrus production areas of the south, these guys have the nickname “Orange Dogs” due to their dietary needs. They can be considered a pest in such situations. Unfortunately, I forgot that, if harassed these guys will evert a pair of bright red structures called osmeterium. The function of these organs appears to be defensive in multiple ways. Often brightly colored, they can look quite like the forked tongue of a snake, and go along with other morphological adaptations in some members of the swallowtails in making them appear like a snake. In addition, numerous chemical compounds can be released with the osmeterium that have been shown to repel ants and other potential insect predators.
Moving from bird droppings to the droppings of a caterpillar we come to this fascinating creature that is most often found on raspberry bushes. A member of the diverse family of beetles – the Chrysomelidae, this Warty Leaf Beetle (Pacybrachis nigricornis), will tuck in its appendages and drop, looking exactly like a caterpillar’s droppings, or “frass” (anyone remember the action figures from the 80s, the Rock Lords?).
Marshall, S.A. 2006. Insects Their Natural History and Diversity. Firefly Books Ltd.
Evans, A.V. 2014. Beetles of Eastern North America. Princetone University Press.
Damman, H. 1986. The osmeterial glands of the swallowtail butterfly Eurytides Marcellus as a defense against natural enemies. Ecol.Entomol. 11: 261-265.