Starting in July dragonflies begin to fill the air. The humidity and heat bring them out in large numbers. They look like tiny helicopters with dual wingspans, or single spanned without an overhead blade. They look like Da Vinci’s inventions:
Above is his drawing of a helicopter. Below his drawing of a wing that one could use to fly.
The order Odonata (“toothed ones”) includes some of the most ancient and beautiful insects that ever roamed Earth, as well as some of the largest flying invertebrates ever to have lived.
Adult Odonata : Adult dragonfly (Anisoptera). Notice the relatively stout body, and the wings extending to each side while the dragonfly is perched. Damselfly bodies are slender by comparison, and wings are held above the body while at rest. Both dragonflies and damselflies belong to the Odonata, which is a subgroup of insects, which in turn is a group of uniramian arthropods. Many characteristics distinguish Odonata from other groups of insects — minute antennae, extremely large eyes (filling most of the head), two pairs of transparent membranous wings with many small veins, a long slender abdomen, an aquatic larval stage (nymph) with posterior tracheal gills, and a prehensile labium (extendible jaws underneath the head). Among living Odonata, there are twentyfive families, mostly dragonflies and damselflies. Of all their characteristics, the easiest way to tell a dragonfly or damselfly from other insects is by the size of the eyes and shape of the abdomen. If the eyes are very large in proportion to the head and the abdomen is long and thin, then it is almost sure to be in Odonata.
Ancient wings : A fossil of Protolindenia wittei, a dragonfly with a wingspan of about 15 cm. This exquisitely preserved specimen comes from the Jurassic Solnhofen limestones of Bavaria, Germany, and is about 155 million years old. The oldest fossils of Odonata are more than twice that old!
The Odonata are known to be ancient insects. The oldest recognizable fossils of the group belong to the Protodonata, an ancestral group that is now extinct. The earliest fossils so far discovered come from UpperCarboniferous (Pennsylvanian) sediments in Europe formed about 325 million years ago.
Dragonflies are generalists, that is, they eat whatever suitable prey is abundant. Oftentimes, they hunt in groups where large numbers of termites or ants are flying, or near swarms of mayflies, caddisflies, or gnats. According to most studies, the main diet of adult odonates consists of small insects, especially Diptera (flies). Maturing dragonfly larvae feed very intensively, as do females when developing their eggs. Studies show that food shortage may limit reproductive behavior. Dragonflies do not hunt in cold weather. Damselflies, however, are not as limited by temperature and have been observed hunting during cold spells. Males are territorial, sometimes patrolling for prey for hours at a time.
Though dragonflies are predators, they themselves must be wary of many predators. Birds, lizards, frogs, spiders, fish, water bugs, and even other large dragonflies have all been seen eating odonates. However, dragonflies have many adaptations enabling them to avoid predation. They have exceptional visual responses and truly agile flight.
This information was taken from the University of California, Berkeley. Technical information compiled by Jason Sabert-Peyman