It is only at the final moult that the sexual organs are mature, the two sexes being alike in the earlier stages of growth.
In the fall the loon (Colymbus glacialis) came, as usual, to moult and bathe in the pond, making the woods ring with his wild laughter before I had risen.
This final moult is effected soon after the insect's appearance in the winged form; the creature seeks a temporary resting-place, the pellicle splits down the back, and the now perfect insect comes forth, often differing very greatly in colours and markings from the condition in which it was only a few moments before.
In the former case it contains numerous grains of sand which are introduced by the animal itself after each moult and which are supposed to act as otoliths.
Nymphs repeat the behaviour of the larvae, and finally moult into the adult, showing the generative orifice, which is the mark of maturity.
Clinging to her hairs they are carried to the nest, where they bore into the body of a bee or wasp larva, and after a moult become soft-skinned legless maggots.
Before a moult actually occurs the cuticle becomes separated from its connexion with the underlying hypodermis.
Of particular zoological interest in this connexion is a Ceylonese genus Dyscritina, in which the cercopods are long, many-jointed and filiform during the early stages of growth, and only assume at the last moult the forcipate structure characteristic of the family.
Certain races moult or cast their skin three times during their larval existence, but for the most part the silkworm moults four times - about the sixth, tenth, fifteenth and twenty-third days after hatching.
It invariably happens during the most active period of feeding, three or four days after the fourth moult up to the rising, and generally appears after a meal of coarse leaves, obtained from mulberries pruned the same year and growing in damp soil.