Difference Between Mayfly And Dragonfly
Mayflies are primitive winged insects of the order Ephemeroptera, usually found near streams, rivers, ponds, and lakes. Among the most ancient insect groups, mayflies have left fossils up to 300 million years old. Typical adult mayflies are up to 2 cm (0.8 in) long, with bulging eyes and two or three long, slender tail filaments. Immature mayflies (nymphs) live underwater, where they breathe through abdominal gills. Some mayfly nymphs prey upon smaller aquatic animals, and others eat plant fragments. Mayfly nymphs are an important food for fish and are excellent fish bait.
After up to 3 years in a nymph stage, the insects emerge from the water, usually at night, and molt (shed their skin) into a winged form that usually molts again into an adult mayfly. Mayflies are the only insects to molt after having wings. Adult mayflies cannot eat, and they live only a few hours or days, during which time they mate and females lay eggs. Huge swarms of mayflies may be attracted to lights and thus become a nuisance, especially near lakeside resorts. Such swarms may appear after an influx of phosphates or other nutrients that increases the volume of the plant materials on which nymphs feed.
Dragonfly, the common name for the graceful long-bodied insects that are most often seen flying swiftly along the borders of lakes and streams. The name is applied particularly to insects of the suborder Anisoptera, but it is also used as a general name for the entire order Odonata, which includes the damselflies. Dragonflies are also called “darning needles.”
The Adult Insect
The head of the adult dragonfly is characterized by two huge compound eyes that occupy more than half of the head’s surface. These eyes are composed of numerous facets and produce a mosaic, or checkerboardlike, type of vision that is very sensitive to moving objects. Small single-faceted eyes, called ocelli, are also present. The dragonfly’s antennae are small and bristlelike, and its mouthparts are modified for biting.
The dragonfly’s thorax, like that of other insects, is composed of three segments. The first segment has two legs and is separate from the other two segments, which are fused together into a large pterothorax bearing two pairs of legs and two pairs of membranous wings. The legs are placed far to the front and are well adapted for perching but not for walking. Their many bristles help to capture small insects in flight. The wings are held horizontally outspread when at rest (in contrast to the damselflies, which hold them vertically above the body).
The long slender abdomen is composed of 10 well-marked segments. The last one in the male ends in three caudal appendages, one below and two above. The lower appendage is often divided, and the two upper ones are modified in various ways. The male genitalia, including the penis, are in a pocket on the underside of the second segment from the thorax, far from the opening of the sperm duct on the ninth segment. This characteristic of the order Odonata is a unique feature among insects. The female abdomen is stouter, ending in two, usually cylindrical appendages, with the genital opening on the ventral side of the eighth segment. Some females have a complicated ovipositor for inserting eggs singly into soft plant tissues.