Odonata
"toothed ones"
Dragonflies, and their cousins, damselflies, are fierce predators of other insects. Dragonflies don't have true "teeth" but they do have strong mandibles with sharply pointed tooth-like serrations.
This website is a culmination of several years of photographing dragonflies at various sites in Olmsted County, mainly at Quarry Hill Nature Center. The purpose of this program is to provide casual observers with a quick identification of common species in Olmsted county. It is not meant to be a scientific treatise on dragonflies. I have not obtained good photographs of some local species (e.g., black saddlebags), but I intend to include them in future versions of this program.
Dragonflies require bodies of water in order to survive. These are most likely to be in the form of ponds or marshes, but also rivers and lakes. The female lays her eggs in water or aqueous vegetation. When the eggs are hatched, dragonflies exist as nymphs (also known as naiads), submerged in water for a year or more. They then re-emerge and undergo their final molt as adult dragonflies.
This program is best visualized on a desktop computer or tablet, but it can also be visualized on a smartphone. To zoom in and scroll on smartphones and tablets, pinch and separate your thumb and index finger on the images.
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Anatomy
Like other insects, dragonflies possess a head, thorax and abdomen. Attached to the thorax are three pairs of legs and two pairs of wings. The legs contain spines which dragonflies can use to gather prey while they are flying.
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The compound eyes (see below) cover most of the head of the dragonfly, and one can assume that a large component of the insect's central nervous system is adapted to analyzing visual activity.t The compound eyes consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells.
Ocelli are primitive, simple eyes which are thought to detect movement.
The pseudopupils (see below) are dark spots in the compound eyes that are thought to result from the reflection of light with reference to the visual axis, since the appearance of the pseudopupil moves across the eye as the insect is rotated.
Pseudopupils
Pseudopupils
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The function of the antennae is uncertain in odonates, but they are thought to provide an assessment of wind direction and velocity to guide the insect through its flight patterns.
The stigma are located on the wingtips. Their function is not definitely known, but they are thought to be vibration dampeners; their extra weight and stiffness may reduce unwanted vibration at the wing tips during flight. They also provide structural support for the wings, along with the nodus.
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"Claspers" (see below) are present in the male to initiate copulation.
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Sexual activity in odonates
The image below depicts the mating behavior among odonates. The male clasps the back of the head of the female with his claspers. The female then flexes the tip of her abdomen (which contains ova) onto the ventral aspect of the male abdomen, which contains sperm cells.
Sexual activity in Dot-tailed Whiteface
Sexual activity in Eastern Pondhawk