The suborder Homoptera contains the cicadas, aphids, and their allies. All these insects have sucking mouthparts, but in each the beak is attached at the back of the head instead of the front of the head as in the suborder Heteroptera. In many species of the Homoptera, each individual has two pairs of wings, both of which are membranous. Probably as many species are without wings, however, as with them. The nymphs are in most respects similar to the adults. Sexual characters, and in some forms wings, gradually develop as the insects approach the adult stage, when development is complete.
Fig. 52.—Neuroptera. Chrysopa nigricornis, a green lacewing. When handled, members of this genus give out a very penetrating and disagreeable odor. Actual length 0.6 inch.
Fig. 53.—Neuroptera. A larva of the genus Chrysopa. This form uses the long jaws to impale aphids and suck their body juices. Actual length 0.5 inch.
This suborder contains a large number of economic pests, including scale insects and leafhoppers, as well as many aphids. In many species of aphids each insect has a pair of tubular structures near the end of the body; these are called cornicles and can be seen in [fig. 47], showing the corn root aphid, Anuraphis maidiradicis (Forbes). In most species of scale insects each individual produces a tough scale, which covers and protects its delicate body, as in [fig. 48], showing the destructive San Jose scale, Aspidiotus perniciosus Comstock. Leafhoppers of many kinds, such as Empoasca fabae (Harris), [fig. 49], are among the destructive pests of beans, potatoes, grapes, apples, and other plants. The treehoppers, spittlebugs, and lanternflies also belong to this suborder.
Megaloptera
Alderflies, Dobsonflies
In this and in the following orders of insects, the life history includes four distinct stages, the egg, the larva, the pupa, and the adult. In the Megaloptera, which include alderflies and dobsonflies, the larvae are caterpillar-like or grublike, and the pupae represent a transformation stage in which the tissues of the larvae are converted to those of the adults. The larvae never have external wing pads; in winged species, these pads first appear externally in the pupae. The adults have long antennae, two similar pairs of net-veined wings, and chewing mouthparts. They are moderately strong fliers. The larvae, [fig. 50], live in streams and lakes; when fully grown they migrate to dry land and pupate in the ground or under the bark of rotten logs.
Typical of the appearance of Illinois alderflies is the adult of Sialis mohri Ross, shown in [fig. 51]. Well known to the fisherman is the hellgrammite, the tough, ferocious, leathery larva found under rocks in streams and prized for bait. This larva matures into the large dobsonfly, Corydalis cornuta (Linnaeus), which often attains a wingspread of 4 inches.