Warbles and Wolves
October 2, 2015. This has been about the gloomiest fall I can remember. We’ve had nearly two weeks of mostly overcast weather, mixed with rain. This morning the sky is a hundred percent overcast with light sprinkles of wet stuff.
From the high boardwalk I watch a squirrel feeding on swamp tupelo fruits on the ground. It has two bare areas on its left shoulder and right flank, each with a noticeable lump the size and shape of a small pecan. These lumps, called “wolves” or “warbles,” contain the larvae of the bot fly, Cutereba. The fly lays its eggs in areas where squirrels are likely to travel and at hatching the small larvae attach themselves to the squirrel and soon burrow underneath the skin. It remains there for three-to-four weeks, feeding on fluids (but not blood) from the squirrel’s body. At maturity it emerges and falls to the ground where it overwinters in the pupal stage, eventually emerging as an adult fly in the spring. The squirrel is rarely affected by its uninvited guest, even when having multiple infestations. Bot fly warbles are prevalent during early fall, when squirrel season first opens, and many hunters discard warble-infected squirrels, thinking the meat is contaminated, which it is not.
A bot fly relative in the tropics includes humans among its hosts, and there is more than one case of a dedicated American entomologist or naturalist returning to the states with the larvae under his or her skin and carrying it to “term” in the name of science. Although the large lump appears painful, the scientists report that it is not, except when the larvae, which has small spines on it, decides to move within its human “cocoon.”
I continue beyond the boardwalk and end up walking along the edge of Hammond Gut. I find my first deer scrapes of the year, freshly made. There are also lots of ripened, brown-green ash seeds scattered on the ground. The first flickers of the fall have moved into the swamp. They are the first of the winter woodpeckers to arrive in autumn, preceding the next-to-follow yellow-bellied sapsucker by about a week.