FIG. 195.—Details of sting of bee: _E_, darts, sheath, and valves; _pb_, poison-bag duct; _fo_, fork; _s_, slide piece; _va_, valve; _b_, barbs. _F_, terminal abdominal segments; _w_, worker’s sting; _q_, queen’s sting; _r_, _r′_, anal plate; _G_, sting entering skin; _sh_, sheath; _a_, _b_, _c_, positions in first, second, and third thrusts with the sting. _H_, portion of poison gland, × 300; _cn_, cell nucleus; _n_, nerve; _g_, ganglionic cell. _I_, portion of the poison gland, cells removed; _cd_, central duct; _d_, individual small ducts; _pr_, tunica propria. _K_, gland of _Formica rufa_; _cd_, central duct; _d_, small ducts; _sc_, secreting cells. _L_, valve and support; _t_, trachea; _va_, valve; _tr_, truss or valve-prop.—After Cheshire. ] [Illustration: FIG. 196.—_A_, rudimentary ovipositor of nymph of Æschna. _B_, the corresponding ♂ structures; _a_, enlarged. _C_, ovipositor of nymph of Agrion; _d_, gill. ] The male genital armature in the bees is originally composed of three pairs of tubercles, homologous with those of the female, all originally arising from three abdominal segments, two afterward being anterior, and the third pair nearer the base of the abdomen. The ovipositor of the dragon-flies (Odonata) is essentially like that of the Orthoptera and Hymenoptera. Thus in Æschna (Fig. 196), Agrion (Fig. 196, _C_), and also in Cicada it consists of a pair of closely appressed ensiform processes which grow out from under the posterior edge of the eighth uromere and are embraced between two pairs of thin lamelliform pieces of similar form and structure.