s is repeated for each layer, from end
to end of the nest.

Let us sum up those structural details, which are not easily grasped
unless one has the nest before one. Lying along the axis of the nest,
and in shape like a date-stone, is the mass of eggs, grouped in layers.
A protective rind, a kind of solidified foam, envelops this core, except
at the top, along the central line, where the porous rind is replaced by
thin overlapping leaves. The free edges of these leaves form the
exterior of the zone of issue; they overlap one another, forming two
series of scales, leaving two exits, in the shape of narrow crevices,
for each layer of eggs.

[Illustration: 1. NEST OF THE PRAYING MANTIS.

2. TRANSVERSE SECTION OF THE SAME.

3, 3a. NEST OF EMPUSA PAUPERATA.

4. TRANSVERSE SECTION OF THE SAME.

5. VERTICAL SELECTION OF THE SAME.

6. NEST OF THE GREY MANTIS.

7. SCHEFFER'S SISYPHUS (see Chap. XII.)

8. PELLET OF THE SISYPHUS.

9. PELLET OF THE SISYPHUS WITH DEJECTA OF THE LARVA FORCED THROUGH THE
WALLS.]

To be present at the construction of the nest--to learn how the Mantis
contrives to build so complex a structure--such was the main point of my
researches. I succeeded, not without difficulty, as the eggs are laid
without warning and nearly always at night. After a great deal of futile
endeavour, chance at last favoured me. On the 5th of September one of my
guests, fecundated on the 29th of August, began to make her preparations
under my eyes, at four o'clock in the afternoon.

One remark before proceeding: all the nests I have obtained in the
laboratory--and I have obtained a good number--have without exception
been built upon the wire gauze of the covers. I have been careful to
provide the insects with roughened stones and tufts of thyme, both being
very commonly used as foundations in the open fields. The captives have
always preferred the network of wire gauze, which affords a perfectly
firm foundation, as the soft material of the nest becomes incrusted upon
the meshes as it hardens.

In natural conditions the nests are never in any way sheltered; they
support the inclemencies of winter, resist rain, wind, frost, and snow,
without becoming detached. It is true that the female always selects an
uneven support on which the foundations of the nest can be shaped, thus
obtaining a firm hold. The site chosen is always the best obtainable
within reach, and the wire gauze is constantly adopted as the best
found