An objection to this view is the fact that the posterior pairs of styles appear to arise both from one and the same segment,—the ninth. Dewitz questions whether the four appendages of the ninth segment represent two pairs of limbs, or one pair split into two branches, and prefers the latter view, but leaves it as a point to be settled by future investigations. As will be seen below, both Kraepelin and Bugnion observed a pair of rudiments to each of the three penultimate segments, those of the middle pair splitting in two. Wheeler maintains, erroneously we think, that the inner of the two pairs on the ninth segment represents the tenth pair of abdominal appendages; but in reality this latter pair become the cercopods. That there are probably originally in insects of all the orders provided with an ovipositor three distinct pairs of appendages, one to each segment, is proved, or at least strongly suggested, by Ganin’s researches on the three pairs of abdominal imaginal discs of the third larva of Platygaster and Polynema (Fig. 188), which are transformed into the ovipositor. He remarks that these imaginal discs have the same origin and pass through the same changes as those in front, _i.e._ those destined to form the thoracic legs. Dewitz has shown that the germs of the ovipositor of the honey-bee arise as buds on the two segments before the last (Fig. 189).
FIG. 188.—Third larva of Polynema: _at_, antenna; _fl_, imaginal buds of the wing; _l_, of the legs; _tg_, buds of the middle pair of stylets of the ovipositor; _fk_, fat-body; _eg_, ear-like process.—After Ganin. ]
FIG. 189.—Imaginal buds and papillæ of the ovipositor of the honey-bee attached to tracheæ; at different stages: _b′_, 1st; _b″_, 2d or middle; and _c′_, 3d pair of papillæ.—After Dewitz. ]
Kraepelin also detected in the larva of the honey-bee a pair of what he regarded as genuine imaginal buds on abdominal segments eight, nine, and ten; the buds on the tenth segment are divided each in two; of these four appendages the two median ones form the barbed sting (_gorgeret_ or _stachelrinne_), and the two lateral stylets, the valves (_stachelscheiden_). The two buds of the ninth segment give rise to the vagina and to the oviducts, and these unite secondarily with the posterior end of the ovaries. The genital appendages of the male correspond to those of the female, and arise from four imaginal buds situated on the under side of the tenth abdominal segment.