Hence the boat-like shape, the smooth hairless body without projections, which easily squeezes its way past obstructions.

The primary larva, with its various appendages closely wrapped against its body by a common sheath, with its fish-like form and its single and only partially movable limb, is perfectly adapted to make the difficult passage to the outer air.
This phase is of short duration.

Here, for instance, a migrating larva shows its head, with its big black eyes, and raises the broken fibres of the entrance.

It gradually works itself forward, but so slowly that the magnifying-glass scarcely reveals its progress.

At the end of half an hour at the shortest we see the entire body of the creature; but the orifice by which it is escaping still holds it by the hinder end of the body.
Then, without further delay, the coat which it wears for this rough piece of work begins to split, and the larva skins itself, coming out of its wrappings head first.