Fig. 138.—The Four Stages of a Botfly, all enlarged.
a, egg on hair of horse (bitten off and swallowed); b, larva; c, larva with hooks for holding to lining of stomach; d, pupal stage, passed in the earth; e, adult horse fly.
RECOGNITION-CHARACTERS FOR THE PRINCIPAL ORDERS OF ADULT WINGED INSECTS
(All are wingless when young, and wingless adult forms occur in all the orders: order Aptera lacks wing-bearing thoracic structures.)
A single pair of wings is characteristic of the order Diptera.
A jointed beak, that is sheath-like, inclosing the other mouth parts, is characteristic of the order Hemiptera.
A coiled sucking proboscis and a wing covering of dust-like microscopic scales are characteristic of the order Lepidoptera.
Horny sheath-like fore wings, covering the hind wings and meeting in a straight line down the middle of the back, will distinguish the order Coleoptera.
Hind wings folded like a fan beneath the thickened and overlapping fore wings, will distinguish most members of the order Orthoptera.
The possession of a sting (in females) and of two pairs of thin membranous wings—the small hind wing hooked to the rear margin of the fore wing—will distinguish the common Hymenoptera.