Mayflies. Adult mayflies are medium-sized, soft-bodied insects with two to three elongate tail-like structures extending from the tip of the abdomen. Their forewings typically are triangular in shape and have numerous veins. The hindwings are small and round or absent. Both pair of wings are held together and straight over the body when the insect is at rest. Adult mayflies lack mouthparts and do not feed; consequently, they are short-lived. Their order name (Ephemeroptera) significantly relates to their mode of life. Ephemero in Latin means one day, and ptera means wings. Some species live just a few hours in the adult stage.
Left. A Mayfly Adult—Characterized by Lack of Mouthparts, Triangular Front Wings and Long Anal Cerci. Courtesy of entomart. Right. Mayfly Nymph or Naiad. Image Dr. Kaae.
The aquatic nymphs or naiads may require a year or two to develop to the adult form. When ready to leave the water and molt into adults, they crawl up on vegetation. This first winged form is not the mature adult (imago), but is called a subimago (unique to this order). A second molt of this adult-like form produces the true adult that is capable of reproduction. Mayfly nymphs feed chiefly on algae with some being predatory. In many areas they are the most common insects in streams and lakes. Being so common, they are extremely important in food chains and are the main diet of many fish, birds, spiders, salamanders, and predatory insects.
In some cases, these insects reach such huge numbers in lakes that the emergence of the adults can become a nuisance. Up until about 40 years ago, dead adults piled as high as five feet were observed along the shoreline and under lights along roads near the Great Lakes. Pollution has greatly reduced these populations. Correspondingly, many species of mayflies are so restricted in their habitat requirements that they are used as a biological indicator of water pollution. This is typically accomplished by periodically recording the nymphal mayfly populations in waterways that are subject to possible pollution. Then, if there is an unexpected reduction in a population, this is a possible indication of pollution.
Dragonflies and Damselflies. Dragonflies are relatively large insects that are characterized by huge protruding eyes, a stalk-like abdomen, well-developed wings with many veins and small hair-like antennae that are not readily visible. Dragonflies and damselflies can be distinguished from each other by the way they hold their wings when at rest. When not in flight, dragonflies hold their wings straight out from the body while damselflies hold their wings folded over the abdomen. Prehistoric dragonflies (200 million years ago) were very similar in appearance to the modern day forms except in some cases they were much larger. There are fossil records of dragonflies with a wing span approaching 3 feet.
Dragonfly Head with Huge Compound Eyes and Hair-like Antennae. Image Dr. Kaae.
Left. Adult Dragonfly with Wings Held at 90 Degree Angle from Body When at Rest. Right.-Dragonfly Nymph. Images Courtesy Dr. Kaae.
Dragonfly and damselfly nymphs (or naiads) are aquatic while the adults are terrestrial but are usually found near water. Nymphal Odonata breathe by means of gills. In damselflies, the gills appear as 3 feather-like structures that protrude from the tip of the abdomen. Gills of nymphal dragonflies are ridged and internally line the rectum. They breathe by drawing water into the rectum and over the gills. This water is subsequently forcibly expelled out the anus. This moves the nymph by jet propulsion or in this case water propulsion.
Nymphal (naiads) and adult dragonflies are predatory. The nymphs feed on a variety of small aquatic organisms. Typically they lie in wait for prey either on a plant or while partially buried in the mud or other aquatic substrates. Even though most naiads feed on smaller insects, some of the larger species are capable of preying on small fish, salamanders and frogs. Occasionally they even become major pests at trout farms.
A common prey of dragonfly nymphs is tadpoles which can be easy targets. There is a form of one species of tadpole (the green tail) that has a rather unique means of survival of the species. In this case, the tadpole's tail is normally developed and therefore relatively small which makes them a relatively slow swimmers and easy prey for these predators. However, if a green tailed tadpole is captured by a naiad, the tadpole releases an alarm pheromone into the water as it is being consumed. Of course, this doesn’t help that tadpole much, but the released chemical triggers other tadpoles of this species to undergo a radical change in their development. One of the significant changes is the formation of huge tails that enhance their swimming speed making them more efficient in escaping from these predators.
Adult dragonflies are considered important in the control of mosquitoes and other flying insects. They are quite agile and can fly as fast as 40 mph. With relatively huge wings and an unusually light abdomen (appears as almost hollow), they possess great ability to maneuver in air. They can hover, shoot vertically upwards and downwards, fly backwards and turn around in the distance of a single body length. Adult dragonflies when actively seeking prey, fly with their legs held in a basket-like fashion that allows them to trap flying insects in the air. Their legs are so highly adapted to aerial capturing of prey that they are incapable of walking. Damselflies are much weaker fliers
The mating behavior of these insects (mainly dragonflies) is to unique, rough, competitive and even dangerous. They are unique from both the standpoint of location of their sex organs and methods of copulation. As with many other insects, the male testes are located at the tip of the abdomen. However, unlike all other insects, the dragonfly penis (aedagus) and a sperm storage pouch are located behind the third pair of legs and in the front of the first abdominal segment abdomen. Before mating, the male approaches the female from above and grabs her behind the head with a pair of claspers on the tip of his abdomen. Once attached and if the now captured female is receptive, she will curl the tip of her abdomen around to align her vagina with his penis thus forming the pair into a hart-like mating position.
A Pair of Damselflies in Mating Position. Image Courtesy of Quartl CC BY-SA 3.0
In addition, mating of dragonflies is quite competitive. It is not uncommon for a male to select a 100-to-200 yard territory along a stream and to patrol that area continuously during most of the daylight hours. Typically it will have 2 or 3 locations (twigs, etc.) along the stream that are preferred for resting. This territory is closely guarded and any other male of the same species that enters the area is quickly chased out. Of course, females are readily accepted. In a few species, the male will actually scoop out any sperm found in the storage area of a female (from previous mating with other individuals) prior to injecting her with his. Finally in a number of species after copulating with a female, the male will not release her with his claspers, but basically flies in tandem with her until she releases her fertilized eggs into the water. In doing so he guards and prevents other males from mating with her prior to oviposition.
Male Dragonfly Holding Female with His Claspers while Flying in Tandem. Image Courtesy Chiswick Chap Creative Commons BY SA 4.0
As previously indicated, mating can be dangerous rough and quite aggressive. In some species the male will actually seize a female out of the air and bite the base of her wings. Others will attempt to breakup mating pair by pulling, ramming and biting them. In some species, damage occurs to the female from the strong claspers of the male. The dragon hunter is notorious for this. The spines of his clasping appendage gouge the female’s exoskeleton, eyes and pierce her head.
Being such large, interesting, obvious and beautiful insects, it follows that they are significant in the cultures of various countries. In some societies, these foul critters are under considerable suspicion. Some are called “ear stickers“, finger cutters,” and “eye pissers”, and in some countries it is believed that they are capable of sewing lips together and even crawling into ears and penetrating the brain. On the other hand, dragonflies in Japan play a significant role in literature and art and are symbolic of victory in battle. In a number of Asian countries, they are consumed as a delicacy. In Indonesia, children go to rice patties with long poles with a sticky substance on the tip. When dragonflies land on the tip (taking advantage of their behavior to rest on twigs), they are incapable of escaping and are collected and served fried with onions. In Thailand and other S.E. Asian countries, the nymphs are strained from streams and served roasted. They are said to taste like crayfish or chicken and are high in protein, low in fat and cholesterol and provide a considerable amount of roughage. Well at least they probably taste like crayfish and are high in protein-I might have gotten a little carried away there!
Stoneflies. The stoneflies are a small group of medium-to-large sized insects that typically are found around streams and lakes. Adult stoneflies can be easily recognized by their overall characteristic shape, well-developed anal cerci, and weakly veined wings that lie flat over the abdomen when the insect is at rest. The adults are feeble fliers, relatively short-lived and frequently seasonal in their appearance. Many species do not feed as adults while others feed on lichen, algae and pollen.