Dragonflies

I always look forward to the first appearance of dragonflies, typically during the first week of June. The reason I like this event is that it also marks the end of the black fly season! I like to think the dragonflies, apex predators of the insect world, are eating all those biting gnats because—well, that would be justice. While it's true that dragonflies eat about a fifth of their own weight in other insects each day there are probably other reasons for the disappearance of the black flies. It may be that the warm weather responsible for the hatch of the dragonflies is inhospitable to the black flies. Or perhaps the final hatch of black flies has simply reached its three-week lifespan. Whatever the reason, it's always cause for personal celebration when I see those early squadrons of dragonflies out patrolling the yard. It means I can put away the insect repellant and take my shirt off to soak up some of that sunshine. According to the UNH Cooperative Extension, there are more than a hundred species of dragonflies in the state, some with beautiful colors, ranging from metallic to pastel. Both the adults and nymphs are predators of other insects. The immature nymphs, which live in water, have an unusual adaptation for predation where the lower mouth parts can suddenly thrust forward to grab prey that is close by, either by ambush or stalking. Both nymphs and adults like to eat mosquitoes or mosquito larva. The adults have large eyes and excellent vision. They have four long transparent, horizontal wings that can operate independently and are quick-reacting, fast fliers that catch prey on the fly using arms that slant upward forming a basket-like scoop. According to National Geographic, they can fly at speeds of 35 MPH. They can also fly backwards and lift off vertically and hover, much like a helicopter. Their compound eyes are so large they almost touch and each has about 28,000 single eyes or ommatidia. Worldwide there are about 7,000 species of dragonflies and they have a 325-million-year history. The nymphs stay in the water for up to three years, hunting aquatic insects. The adults only live for about a month. Outdoors people who dread those biting deer and horse flies sometimes employ a "scarecrow" fake dragonfly attached to a hat to repel those biters. This works because deer flies and horse flies are visual hunters who know they are prey for dragonflies. Not to be confused with dragonflies, damselflies are a smaller cousin. Damselflies have slender bodies, vivid colors and long, filmy net-veined wings. Thay are also aerial predators of other insects and may themselves be prey for dragonflies. One major difference is the way they hold their wings when at rest. Dragonflies hold their wings horizontally, while damselflies hold theirs together, vertically. If you're not fortunate enough to have dragonflies patrolling your yard, be advised you can find them in close proximity to most wetlands where they're likely busy keeping the mosquito population in check.