The only Mantis that I have been allowed to observe while engaged in laying does her work upside down, hanging from the top of the cage. My presence, my magnifying-glass, my investigations do not disturb her at all, so great is her absorption in her labour. I can raise the trellised dome, tilt it, turn it over, spin it this way and that, without the insect’s suspending its task for a moment. I can take my forceps and lift the long wings to see what is happening underneath. The Mantis takes no notice. Up to this point, all is well: the mother does not move and impassively endures all the indiscretions of which I am guilty as an observer. And yet things do not go quite as I could wish, for the operation is too rapid and is too difficult to follow. The end of the abdomen is immersed the whole time in a sea of foam, which prevents us from grasping the details of the process with any clearness. This foam is greyish-white, a little sticky and almost like soapsuds. When it first appears, it adheres slightly to a straw which I dip into it, but, two minutes afterwards, it is solidified and no longer sticks to the straw. In a very short time, its consistency is that which we find in an old nest. The frothy mass consists mainly of air imprisoned in little bubbles. This air, which gives the nest a volume much greater than that of the Mantis’ belly, obviously does not come from the insect, though the foam appears at the entrance of the genital organs; it is taken from the atmosphere. The Mantis, therefore, builds above all with air, which is eminently suited to protect the nest against the weather. She discharges a sticky substance, similar to the caterpillars’ silk-fluid; and with this composition, which amalgamates instantly with the outer air, she produces foam. She whips her product just as we whip white of egg to make it rise and froth. The tip of the abdomen, opening with a long cleft, forms two lateral ladles which meet and separate with a constant, rapid movement, beating the sticky fluid and turning it into foam as it is discharged outside. In addition, between the two flapping ladles, we see the internal organs rising and falling, appearing and disappearing, after the manner of a piston-rod, without being able to distinguish their precise action, drowned as they are in the opaque stream of foam.