photo J.K. Clark

Description: Adult hover flies are generally brightly colored-with black-and-yellow abdominal bands-and closely resemble bees or wasps. They're typically ½- to ¾-inch long and have two wings. Their larvae, which can reach ½-inch in length, are sluglike, tapered toward the head, and generally marked with a yellow longitudinal stripe on the back. Tell-tale black, oily smears of excrement on plant foliage reveal their presence.

Life cycle: Hover flies lay their whitish to gray oblong eggs singly on their sides near or within aphid colonies. They can have many generations per year.

Key benefits: Nonbiting, nonstinging adult hover flies feed on pollen, nectar, and honeydew from aphids and scale insects. Their larvae consume aphids and other small, soft-bodied insects, including thrips and small caterpillars. A single larva can eat hundreds of aphids in a month. Hover fly larvae can detect low numbers of aphids and are particularly useful early in the season.

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