A gnat pupa swims through the water by powerful strokes of its abdomen, while the caddis-fly pupa, in preparation for its final ecdysis, bites its way out of its subaqueous protective case and rises through the water, so that the fly may emerge into the air.
The sub-imago of the Ephemeroptera suggests that a moult, after the wings had become functional, was at one time general among the Hexapoda, and that the resting nymph of the Thysanoptera or the pupa of the Endopterygota represents a formerly active stage in the life-history.
But the pupa hangs from the surface by means of paired respiratory trumpets on the prothorax, the dorsal thoracic surface, where the cuticle splits to allow the emergence of the fly, being thus directed towards the upper air.
After a resting (pseudo-pupal) stage and another larval stage, the pupa is developed.
Some pupae are thus more active than some nymphs; the essential character of a pupa is not therefore its passivity, but that it is the instar in which the wings first become evident externally.
Cuticle of pupa or puparium splitting longitudinally down the back, to allow escape of imago.
Fixed to the body as in the pupa of a moth, and the likeness of pupa to perfect insect is very close.
The pupa stage of the ant-lion is quiescent.
The growth of the worms during their larval stage is thus stated by Count Dandolo: - When the caterpillars are mature and ready to undergo their transformation into the pupa condition, they cease eating for some time and then begin to ascend the brushwood branches or echelletes provided for them, in which they set about the spinning of their cocoons.
A, Female; b, female after loss of wings; c, male; d, worker; e, larva; g, pupa (magnified four times); f, head of larva more highly magnified.