GOLDEN SCARABAEI CUTTING UP A LOB-WORM.] The foamy mass consists chiefly of air imprisoned in minute bubbles.
This air, which gives the nest a volume very much greater than that of the abdomen of the Mantis, evidently does not issue from the insect although the foam appears at the orifice of the genital organs; it is borrowed from the atmosphere.

The Mantis builds more especially with air, which is eminently adapted to protect the nest against changes of temperature.

She emits a glutinous substance like the liquid secretion of silk-worms, and with this composition, mixed instantaneously with the outer air, she produces the foam of which the nest is constructed.
She whips the secretion as we whip white of egg, in order to make it rise and stiffen.

The extremity of the abdomen opens in a long cleft, forming two lateral ladles which open and shut with a rapid, incessant movement, beating the viscous liquid and converting it into foam as it is secreted.

Beside the two oscillating ladles we see the internal organs rising and falling, protruding and retreating like a piston-rod, but it is impossible to observe the precise nature of their action, bathed as they are in the opaque blob of foam.
The end of the abdomen, continually palpitating, rapidly closing and opening its valves, oscillates right and left like a pendulum.