The only Mantis that I was able to observe at the moment of laying her eggs worked upside-down, clinging to the wire near the top of the cover.  My presence, my magnifying-glass, my investigations did not disturb her in the least, so absorbed was she in her labours.  I was able to lift up the dome of wire gauze, tilt it, reverse it, turn it over and reverse it again, without causing the insect to delay her task for a moment.  I was able, with my tweezers, to raise the long wings in order to observe rather more closely what was taking place beneath them; the Mantis took absolutely no notice of me.  So far all was well; the female did not move, and lent herself impassively to all the indiscretions of the observer.  Nevertheless, matters did not proceed as I had wished, so rapid was the operation and so difficult observation.

The end of the abdomen is constantly immersed in a blob of foam, which does not allow one to grasp the details of the process very clearly.  This foam is of a greyish white, slightly viscous, and almost like soapsuds.  At the moment of its appearance it adheres slightly to the end of a straw plunged into it.  Two minutes later it is solidified and no longer adheres to the straw.  In a short time its consistency is that of the substance of an old nest.

[Illustration:  1.  THE MANTIS DEVOURING THE MALE IN THE ACT OF MATING.

2.  THE MANTIS COMPLETING HER NEST.

3.  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.