Primitive Winged Insects
The primitive winged insects cannot fold their wings, which in repose are held erect over the body or straight out from the sides, as illustrated in figs. [26] and [29]. Although many types of these insects lived in bygone ages, only two orders have survived to the present. Both occur abundantly in Illinois.
Ephemeroptera
Mayflies
A group of insects in which the nymphs or young live in streams and lakes; the adults are found along the edges of the streams or lakes from which they have emerged. Mayflies are unique in that the full-grown nymphs molt into winged insects that are not quite mature and that molt again, usually the next day, when they emerge as fully mature adults. The nymphs are varied in shape and have short antennae, long legs, which are often flattened, and three tails at the end of the body. The adult flies have very long front legs, short antennae, practically no mouthparts, usually two pairs of wings, and two or three long tails. When a mayfly is at rest, the wings are held together above the body. Hexagenia limbata (Serville), figs. [26] and [27], is one of the very common Illinois mayflies and is an important factor in the food economy of many fish.
Mayflies, formerly called Plectoptera, together with stoneflies, caddisflies, and midges, constitute a very large portion of the life of our lakes and streams; all four groups are important as fish food.
Odonata
Dragonflies, Damselflies
Another order in which the nymphs develop in streams, lakes, or ponds, and in which the adults are aerial. The nymphs have short antennae, long legs, and either a stout body with no tail, as in Anax junius (Drury), [fig. 28] (dragonfly nymph), or a slender body with three large leaflike gills projecting from the end of the body (damselfly nymph). A most distinctive feature of this order is an extensile, highly modified lower lip that fits like a mask over the face of a nymph. The lower lip is hinged to extend forward and seize the small animals upon which the nymph lives. The adults are large, often beautifully colored, as is the Tramea lacerata Hagen, [fig. 29]. They have chewing mouthparts and two pairs of large wings, very finely and intricately netted with veins.
Fig. 26.—Ephemeroptera. Hexagenia limbata, the adult form; this mayfly is also called shadfly or willowfly. Mayflies sometimes emerge in great swarms and congregate in piles around bridge or city lights. Actual length about 1.0 inch.
