The larva escaping from the hinder ranks has to squeeze past the empty shells, still in position, of the eggs which have already hatched, so that the narrowness of the passage is increased by the empty egg-shells.

Under these conditions the larva as it will be presently, when it has torn its temporary wrappings, would be unable to effect the difficult passage.

With the encumbrance of antennae, with long limbs spreading far out from the axis of the body, with curved, pointed talons which hook themselves into their medium of support, everything would militate against a prompt liberation.

The eggs in one chamber hatch almost simultaneously.

It is therefore essential that the first-born larvae should hurry out of their shelter as quickly as possible, leaving the passage free for those behind them.