Tiny Dancers

Yesterday was warmish and sunny. I was on my deck, checking out the bird feeders, when I noticed movement like drifting dust motes in the long afternoon shadows over the azaleas. The motes were tiny mosquito-sized insects, bobbing up and down as if on invisible foot-long yo yo strings. The first question that popped into my mind was What are they?, followed by Why are they here? and Why are they here now? and finally, What the heck are they doing? I consulted my library and did some research on the net. That, plus a couple of calls to entomologist acquaintances, gave me an answer as to identity. They were Winter Crane Flies (family Trichoceridae for those keeping score), one of about 30 species in North America. My entomology text says "Usually seen in the fall or early spring, and some may be seen on mild days in winter. Adults form swarms, consisting mostly of males, over bushes or high places. The larvae occur in decaying vegetable matter". That was pretty much it. Okay, I thought, I know a little about what; maybe I can guess the rest, or at least make a reasonable inference.

They are here due to the abundance of larval habitat; dead rotting leaves. Larvae chomp their way through compost and damp leaf piles, pupating when the temperatures go below freezing and come out as reproductive adults as soon as it gets warmer. Adults do not eat. They are here to find a mate and reproduce, living on stored nutrients, like animated batteries.

They are here now because, duh, it's winter. Although most insects spend the winter as immatures (egg, larva, pupa) or hibernating adults (some butterflies), a few species can be seen on all but the most bitter days if you know where to look. If you can manage not to freeze, being a winter adult insect has advantages. One being few predators; birds are foraging for calories, not protein for their chicks, and insect predators like dragonflies are hiding out as the above mentioned immatures and not on the wing. Small size is an advantage as well; you are not worth the energy expenditure for a warm blooded predator such as a chickadee to bother with.

What they are doing pretty much all boils down to sex. The clue being the "Adults form swarms, consisting mostly of males, over bushes or high places" part. Although I haven't found anything in the literature, I'm reasonably sure the swarms consist mostly of lekking males. Leks are aggregations of males gathering for the sole purpose of attracting a mate. Leks are very efficient if your species is spread thinly on the ground. Males of many species form leks -Peacocks, Birds of Paradise, and Prairie Chickens lek, as do some bats and a few other insects such as solitary bees. Great Hammerhead Sharks gather over submerged mountains, coming from hundreds of miles around to form "breeding aggregations" which are probably leks. A lek is nature's equivalent of a singles bar, where (mostly) males congregate and do their damnedest to impress a female into choosing them for a partner. Males compete for females by showing off. Gaudy plumage, loud hoots, or, in the case of Winter Crane Flies, dancing. "Look at me" they are saying to cruising females, "I can bounce higher than the rest of the guys here, pick me." The advantage is that the female can pick and choose the best dancer with the best genes (he's the one bouncing highest, or at least the most enthusiastically), and mate with him. She doesn't even have to go home with him. Females are attracted to groups of males rather than to a single male, so swarming together, or hooting together, or shaking your gaudy plumage together, or trying to look your coolest in the same bar together increases your chances a female will seek you out. Or at least choose someone. Since most males in a lek are related and share at least some genes (except in most bars), even if you don't get picked, you can still get some of your genes out to the next generation just by being there.

Spring, or in this case, mild winter days, and a young Winter Crane Fly's fancy turns to thoughts of love. So get on your dancing shoes, all six, and join a lek. Who knows, you might get lucky.