Prehistoric monsters are flying around your backyard. They’re probably out there this very afternoon, terrorizing your airspace. They have ferocious teeth. They’re at the top of the food chain, they’re hungry, and they’re everywhere.

Luckily, they do not eat humans. Also, they are only an inch or 2 long – the colorful winged helicopters that dart through the air from June to about mid-September: dragonflies.

When you notice them flitting nimbly around your yard, you’re watching a scene from before the dinosaurs. Dragonflies are one of the oldest species still living direct from their origins. While the first dinosaur fossils are about 240 million years old, the earliest remains of a dragonfly date to about 320 million years ago. (Humans, in roughly the form we understand ourselves, have been around about 2 million years.)

Some of those early dragonflies had 2-foot wingspans, which means they were monstrous even to human-size creatures. While the dinosaurs disappeared around 65 million years ago, possibly in cataclysmic climate changes after an asteroid or other piece of space debris crashed into the Earth, dragonflies continued to flourish at scaled-back sizes.

To us nowadays they are pesky miniatures, but they’re still howling monsters to the mosquitoes, gnats and flies they eat. Dragonflies can’t walk, only perch; they catch their food by arranging their spiny legs to form a sort of net. Among the most superb fliers in nature, they dart around snaring small insects, and eat on the fly, tearing off chunks of bug meat with teeth that might seem nightmarish to a mosquito, if the mosquito could think about it. Their teeth are so prominent a feature that naturalists used the Greek word for tooth, “odon,” as the basis for the name of their scientific order, odonata. Other people just call them mosquito hawks.

The ancient dragonflies have about 5,000 species of descendants, about 450 of those species inhabiting North America. There actually are two main kinds of dragonflies, told apart fairly easily: there are the dragonflies, which are the heftier, often colorful ones, and the damselflies, which have slimmer abdomens. The dragonflies come in families such as darners (the large, brilliant blue and green ones), clubtails (with expanded tail ends), and skimmers (with patterned wings and more squat bodies), all of which, with others, are commonly seen in Maine. One thriving South American species of dragonfly has a 7-inch wingspan.

Dragonflies spend only a brief month or two flying around as adults. In the earlier stage of their life, they are six-legged bugs. They jet around in water and wait for food to stray too near their mouths. This “naiad” stage can last two or three years before they metamorphose into four-winged creatures who spend one short summer netting gnats, and mating. Yes, when you see two dragonflies joined at one or both ends, they’re probably doing what you think.

When dragonflies and damselflies seem to be buzzing you at your picnic table, don’t worry. The darners don’t really sew up your lips if you tell a lie. They’re not after you, but looking with their 28,000-lens eyes for mosquitoes, who are after you. Like the descendants of the first working helicopter, which Igor Sikorsky shaped after them, the dragonflies are just patrolling, as they’ve done for 300 million years.