March 7, 2016
Phorid flies are 1 to 3 mm long insects that most people probably never see. They are busily at work in your backyard, decomposing, parasitizing, pollinating, and doing all the other things that small insects do. But people don’t care about them...how could they? They don’t even know they exist! In the Urban Nature Research Center, I get comments all the time, or even looks from some of my colleagues that say “they are only flies”, or “there is more to the world than phorid flies”. Why, it is insinuated, can’t we just base conservation decisions on things people care about, like birds and mammals?
The problem with this idea is that birds and mammals are large, highly mobile creatures, like us. Although we tend to admire creatures that are most like us, in some ways they are the worst indicators for local conditions. After all, what tells you more about your backyard-a fly that never strays farther than one meter from the dead mushroom it was reared from, or the red tailed hawk that soars across half the basin in the afternoon? Small creatures give us information on a finer level than the large ones do. Insects like phorid flies have faster generation times as well. That red tail may be five years old, but you know that fly hatched within the last year, and represents conditions that occurred this year only.
Finally, insects give us an incredible amount of knowledge because there are so many of them. In the book Insects of the L.A. Basin, Charles Hogue estimated that there were 2-to-3000 species of insects in Los Angeles. By studying phorid flies in detail, we know now that Charlie was way off. Here we can do the math: our study has found about 100 species of phorid flies in Los Angeles. Flies make up about 16% of the worlds insect biodiversity, and phorids make up about 1/40 fly species worldwide. We know that phorids are incredibly more diverse than one in 40, however, so let’s say one in 20 (.05). One hundred local species equals .05 of the 16% of insects that are Diptera, so 100 equals .05×16% of “x” (the total number of insect species). This calculates out to the staggering 12,500 species of insects in Los Angeles, most of which are probably not described! That means there are legions of tiny beetles, wasps, gall midges, and other unassuming creatures sharing our city, going about their business, maintaining the environment. It is our own private army of ecosystem service providers. Oh, and by the way, phorid flies are incredibly cool. All images by Kelsey Bailey.