Garden Allies: Fabulous Flies

Today, I watched a tachinid fly larva emerge from a monarch caterpillar. It was gross and fascinating, and I was a bit sad for the poor dead not-to-be butterfly. It made me reflect, as I often do when writing “Garden Allies,” on our attitude towards insects. I am frequently asked, “How can I recognize the good bugs?” The longer I study nature, the harder it is to give an easy answer. “Good,” “bad,” and even “pest” and “beneficial” are not really relevant in the context of a healthy food web. OK, I admit, once I taught a class entitled The Good, the Bad, and the Ugly—who could resist? Of course, sometimes insects are pests when they damage plants we value beyond a threshold we find acceptable. Ladybugs are deemed beneficial when they eat the aphids (pests!) on our roses. But would we look at them differently if there were no aphids to control?

Long-legged fly (Condylostylus longicornis) from the family Dolichopodidae. Illustration: Craig Latker

When I comment that every living organism, even a tiny insect, has its place in the web of life, the retort is usually, “So what good are flies?”  It would take mor...