EPHEMEROPTERA

Order Ephemeroptera (eff-em-err-op'-terr-uh), the mayflies. Mayflies are delicate, soft-bodied, small to medium sized insects whose adults live for a very short time.

Mayflies undergo incomplete metamorphosis (hemimetabolous). Nymphal mayflies are aquatic and are often called naiads. Most have feather-like or leaf-like gills along the sides of the abdomen. The abdomen bears two or three "tails," either (a) two long cerci and one caudal filament or (b) just the two cerci. The nymphs have chewing mouthparts and gills on the abdomen. The adults have vestigial mouthparts and do not feed. The antennae are bristle-like (setaceous). They are fairly large in nymphs, but they are tiny, nearly invisible, in adults. Insome species, the males have greatly elongated front legs to aid in mating.

When mature, a mayfly nymph rises to the water's surface and molts to a winged form, the sexually immature subimago. After emerging, the subimagos fly to shore and molt into the adult stage. Thus, Ephemeroptera are the only insects that molt after attaining functional wings. The adults then mate, lay eggs, and die, all within a very short time. This may require only a few hours, or it might take several days, depending upon the species. The aquatic nymphs, however, may require two or three years to develop. Subimagos (also called subimagines) are known to fly fishermen as duns or spinners.

The fragile, somewhat triangular wings are membranous and have many veins. The hind wings are much smaller than the front wings. In some species, the hind wing is absent. At rest, the wings are held together vertically over the body. The Ephemeroptera and Odonata (dragonflies and damselflies) can not "flex" their wings, i.e., bring them back and hold them flat or roof-like over the body. Collectively, therefore, Ephemeroptera and Odonata can be referred to as the Paleoptera, the "ancient-winged" insects. All other insects can flex their wings and are referred to as the Neoptera, the "new-winged" insects. These terms imply that the wing flexure mechanism developed more recently ("neo-") than non-flexure ("paleo-").

Ephemeroptera are valuable members of the food web, especially in aquatic habitats. They serve as food for many fish, amphibians, birds, and predaceous insects. The nymphs feed mostly on algae and organic matter (detritus) but a few are predaceous and feed on other insects. Having vestigial mouthparts, the adults do not feed. Mayflies are sometimes a nuisance pest when the subimagos and adults emerge in enormous numbers. This is about their only direct economic impact.

ODONATA

Order Odonata (o-don-ate'-uh), the dragonflies and damselflies. These familiar insects have two pairs of elongate, membranous wings with a complex network of small cross veins. The leading edges of the wings usually have a dark, thickened area called a stigma. There is a short, thick cross vein, the nodus, in the basal one-third or one-half of the wings. Where the nodus reaches the leading edge of the wing, the wing appear notched or slightly broken. Odonata are paleopterous, hemimetabolous insects with chewing mouthparts. The compound eyes are large and occupy much of the head. The three-to-five segmented antennae are bristle-like (setaceous) or very small thread-like (filiform) and usually quite difficult to see. The thorax is relatively small, and the prothorax is often much reduced. The abdomen is long and slender and, in the male, has short, unsegmented terminal claspers These are not cerci; the cerci are generally reduced or even absent.

Odonata nymphs (naiads) are aquatic. Both immatures and adults are predators. The nymphs feed on most small aquatic organisms, including insects and very small fish. Their labium is modified into an elongate, hinged , prehensile organ with which they capture their prey. The adults, aided by the basket-like arrangement of their legs, feed on small insects captured in flight. Although the adults may roam far from water, they must return to water to reproduce. Some species lay their eggs on the water's surface, some beneath the surface, and some insert their eggs into aquatic plants.

The order Odonata is divided into two readily distinguishable suborders:

PLECOPTERA

Order Plecoptera (plee-cop'-terr-uh). The name refers to the fact that the hind wing is folded, like pleats, when at rest. The Plecoptera, common name stoneflies, are hemimetabolous and neopterous. They are somewhat flattened, medium to large, soft-bodied insects. They have long, prominent, filamentous or threadlike antennae and prominent, slender cerci. There is no medial caudal filament. The cerci are often hidden by the membranous wings which are held flat over the abdomen at rest. However, sometimes the cerci extend beyond the wing tips. In most species, the front wing is elongate and rather narrow while the hind wing is much wider. Stoneflies are not very strong fliers, and some species have secondarily wingless adults. The mouthparts are the chewing type; they are often weakly developed or vestigial in adults that do not feed. Those adults that do feed eat algae and lichens.

Most stonefly adults are summer insects, but some species are active in the winter. Economically, stoneflies have about the same role as mayflies.