Day 1: The wasp larvae (right) emerge from the moth caterpillar (left).
Over the next two days, they first faded to a dull yellow...
Day 2: The wasp larvae begin to pupate.
...and then shriveled and blackened.
Day 3: The wasp larvae have become pupae.
However, the wasps were not sickening and dying -- they were progressing normally through their development from larvae to pupae. Meanwhile, the moth caterpillar that stood by, apparently healthy except for its inertia, had its own development frozen. To be continued...
This Halloween, instead of featuring a seasonable insect or spider, I will share a spooky story of a "possessed" caterpillar.
Parasitoids may be among the smaller enemies that a caterpillar has, but they are also among the most insidious. When a female parasitoid (generally a small wasp or fly) finds a suitable caterpillar, it lays its eggs on or even inside the caterpillar. The parasitoid larvae then emerge from the eggs and proceed to feed on the caterpillar. What becomes of the caterpillar once the parasitoid invasion is complete? It may be mummified, vanish from inside a fuzzy shroud, or perhaps more strangely -- be left apparently unharmed.
A copper underwing (Amphipyra pyramidoides) caterpillar and recently emerged parasitoid wasp larvae.
The light green caterpillar shown above and below is surrounded by the darker green larvae of a parasitoid wasp. The wasp larvae had recently finished feeding inside the caterpillar and had broken through the sides of the caterpillar to finish their development outside.
The slits that the wasp larvae emerged through are visible behind them.
Meanwhile, the caterpillar just sat there as if unperturbed by the litter of parasitoids.
However, the caterpillar was hardly passive. When the parasitoid larvae were threatened by an approaching object, the caterpillar became surprisingly aggressive.
The parasitoids had left the caterpillar alive, but not at liberty. Though the caterpillar was no longer needed as food, it could still be manipulated into serving as the parasitoids' protector.
However, by the next day, all the adults were gone. I thought that they might just have gone into hiding for the daytime, but they had not returned to the bindweed by the time I checked again in the evening -- or any time later. They had left something of themselves behind, though!
Tortoise beetle eggs attached to the underside of a bindweed leaf.
Like spittlebugs, tortoise beetle larvae conceal themselves underneath an excretion of the plant material that they eat. However, since the beetle larvae feed on leaves rather than sap, the end product is not nearly as elegant as the spittlebugs'...
A tortoise beetle larva with its fecal shield raised.
...nor is the process of making their coverings.
A tortoise beetle adding to its shield.
Yet regardless of aesthetic objections, the fecal shields seemed to be quite adequate for the purpose of protecting the larvae, which thoroughly infested the bindweed in the garden without attracting any predators or parasites (as far as I could see).
Three tortoise beetle larvae on a mostly eaten bindweed (Convolvulaceae) leaf.
However, as they built their shelters, they were exposed on the exterior of the leaves.
A caterpillar, probably of a tortricid moth (Tortricidae).
One of the vulnerable caterpillars exhibited evidence of a recent attack: two parasitoid eggs attached to its body.
A caterpillar with two parasitoid eggs on it.
Even if this caterpillar escaped the attention of predators and hid itself within the leaves, it was probably the parasitoid larvae that benefited from the shelter in the end.
