Through this temporary protection the active pupa, which closely resembles the mature insect, subsequently bites a way by means of its strong mandibles, and rising to the surface of the water casts the pupal integument and becomes sexually adult.
After another moult the insect passes into the passive nymphal or " pupal " stage, during which it takes no food and rests in some safe hiding-place, such as the soil at the base of its food-plant or the hollow of a leaf-stalk.
Some members of this order spend the winter in the adult state, others in the " larval " or " pupal " condition.
In this it remains until the completion of the transformation into the sexually mature insect, which then emerges from the case, leaving the pupal integument behind.
Meinert, who endeavoured to compare them with the tegulae of Hymenoptera, but the older view was securely established by the demonstration in pupal elytra by J.