Beneficial Because:
Adult female tachinid flies lay their eggs on or in other insects, from beetles to grasshoppers. The eggs quickly hatch, and the fly larvae feed inside their host, weakening or killing it. Tachinid flies are important parasites of numerous caterpillars and other leaf-eating insects.
Food and Habitat:
Adult tachinid flies eat a liquid diet of flower nectar and insect honeydew. These fast-flying insects patrol the garden for hosts for their young during the day and rest in foliage at night. On sunny days, open spaces or hilltops that are buzzing with groups of flies are often tachinid flies meeting to mate. Tachinid flies overwinter as slender brown pupae in the soil.
Attracting More:
Gardens that include a diversity of plants often attract plenty of tachinid flies, which also visit compost projects in which other insects are active.