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Bug of the Month: Drone fly
Common name: Drone fly
Latin name: Eristalis tenax
Flower flies in general
Flower flies (Family Syrphidae), also known as "hover flies," are commonly mistaken for bees or wasps. This is because they are often seen on flowers harvesting nectar and pollen (as bees do), they buzz like bees, and many species look like bees too, with yellow and black stripes or patterns. Some syrphids are large and fuzzy like bumble bees, some are smooth and look very much like yellowjackets or other stinging wasps. Unlike the wasps and bees they mimic to avoid predation, however, flower flies do not possess a stinger. Other obvious differences include their hovering flight, and, like all true flies, they possess only one pair of wings.
The larvae (immature stage) of flower flies are found in many different habitats, and are very diverse in feeding habits; they include predators, scavengers, plant-feeders, dung-feeders, and aquatic filter-feeders. Flower flies are common, abundant, and many are very important economically as pollinators or predators of aphids and other pests. Flower flies occur world-wide, except at extreme southern latitudes; there are approximately 900 species in North America. We have documented 14 species on the Boston Harbor Islands so far, but we have many more awaiting identification!
How to identify drone flies
Technically, the family Syrphidae can be told apart from other flies by the presence of a "false vein" (sometimes more of a crease), that runs along the middle of the wing. This is impossible to see in a hovering fly! Drone flies are large (1/2 inch) flower flies that look very much like honey bees. They resemble bees not only in their appearance but also by the loud droning sounds they make as they hover above flowers. Drone flies can be told apart from honey bees by the single pair of wings, the black, hourglass-shaped pattern on the rear portion of their abdomen, and by their much larger eyes (which have two vertical bands of short hairs in this species).
Where to find drone flies on the Boston Harbor Islands
Drone flies are extremely common and adults can be seen flying around on the islands from late spring to late autumn, often hovering near flowers where they feed. Look for them in open meadows or along sunny trails.
How drone flies make a living
As adults, drone flies feed on nectar as an energy source and on pollen for protein (much like bees). While they lack the pollen buckets of bees, pollen sticks well to their hairy bodies, and is easily transported to other plants. The immature larvae (maggots) of drone flies live in muddy, nutrient-rich, oxygen-poor pools of water, like drainage ditches, where they feed on decaying matter. They are called rat-tailed maggots because they have a long, snorkel-like tube that extends from the rear end of their body up to the water surface. This breathing tube allows the maggots to remain under water without surfacing for oxygen.
Where in the world drone flies occur
Drone flies were introduced to North America from Europe and now are commonly seen throughout the continent. Because the larvae are able to tolerate relatively polluted conditions, drone flies are often found near humans and have been introduced to many parts of the world.