Fig. 579.—Pupa libera of neuropterous insects a, Corydalus cornutus; b, Sialis; c, Hemerobius.
The male Coccid anticipates the metabolous insects in passing through a quiescent state, when, as Westwood states, it is “covered by the skin of the larva, or by an additional pellicle.” The body appears to be broad and flat, the antennæ and fore legs resting under the head, while the two hinder pairs of legs are appressed to the under side of the body. There is but a slight approach to the pupa libera of a metabolous insect.
Riley states that the male larva of Icerya purchasi forms a cocoon waxy in character, but lighter, more flossy, and less adhesive than that of the female egg-cocoon. It melts and disappears when heated, proving its entirely waxy nature. When the mass has reached the proper length, the larva casts its skin, which remains in the hind end of the cocoon, and pushes itself forward into the middle of the cocoon. The pupa (Fig. 581) is of the same general form and size as the larva. All the limbs are free and slightly movable, so that they vary in position, though ordinarily the antennæ are pressed close to the side, as are the wing-pads; the front pair of legs are extended forward. “If disturbed, they twist and bend their bodies quite vigorously.” The pupa state lasts two or three weeks. A similar pupa is that of Icerya rosæ. (Riley and Howard.)
Fig. 580.—Pupa obtecta of Diptera: a, Ptychoptera; b, Tabanus atratus; c, Proctacanthus philadelphicus; d, Midas clavatus.
Fig. 581.—Pupa libera of Icerya purchasi, ventral view.—After Riley, Insect Life.
The metamorphosis of Aspidiotus perniciosus is of interest. The male nymph differs much after the first moult from the female, having large purple eyes, while the female nymph loses its eyes entirely. It passes into what Riley terms the pro-pupa (Fig. 582, b), in which the wing-pads are present, while the limbs are short and thick. The next stage is the “true pupa” (Fig. 582, c, d), in which the antennæ and legs are much longer than before. There is no waxy cocoon, but only a case or scale composed of the shed larval skin, i.e. “with the first moult the shed larval skin is retained beneath the scale, as in the case of the female; with the later moultings the shed skins are pushed out from beneath the scale,” and when they transform into the imago they “back out from the rear end of their scale.”
