Fig. 4—Development of sting of the bee: A and C, ventral; B, side view. A, End of abdomen of adult larva: a, b, c, d, the last four segments, c being the eleventh body segment, 11; b bearing two pairs, and c one pair, of rudiments. B, Tip of abdomen of adult bee: 9, the ninth, d, the tenth body segment. C, Rudiments in the early condition as seen within the body: c, first pair; b, the second pair not yet divided into two pairs; b″, c′, commencement of external growths from the internal projections. (After Dewitz.)
Dewitz has also traced the development of the thoracic appendages in Hymenoptera.[[8]] Although no legs are visible in the adult larva, they really arise very early in the larval life from masses of hypodermis, and grow in the interior of the body, so that when the larva is adult the legs exist in a segmented though rudimentary condition in the interior of the body. Dewitz's study of the wing-development is less complete.
Four primary divisions of Aculeates are generally recognised, viz. Anthophila (Bees), Diploptera (Wasps), Fossores (Solitary Wasps), Heterogyna (Ants). Though apparently they are natural, it is impossible to define them by characters that are without some exceptions, especially in the case of the males. Ashmead has recently proposed[[9]] to divide the Fossores; thus making five divisions as follows:—
Body with more or less of the hairs on it plumose .......... 1. Anthophila.
Hairs of body not plumose.
Pronotum not reaching back to tegulae .......... 2. Entomophila [= Fossores part].
Pronotum reaching back to tegulae.
Petiole (articulating segment of abdomen) simple without scales or nodes.
Front wings in repose with a fold making them narrow .......... 3. Diploptera.