But does the Mantis really employ two secretions?
No.

Anatomy, in the first place, assures us of the unity of the materials of the nest.

The organ which secretes the substance of the nest consists of cylindrical tubes, having a curious tangled appearance, which are arranged in two groups of twenty each.
They are all filled with a colourless, viscous fluid, which is precisely similar in appearance in all parts of the organ.

There is no indication of any organ or secretion which could produce a chalky coloration.
Moreover, the method by which the snowy band is formed rejects the idea of a different material.

We see the two caudal appendices of the Mantis sweeping the surface of the foamy mass, and skimming, so to speak, the cream of the cream, gathering it together, and retaining it along the hump of the nest in such a way as to form a band like a ribbon of icing.
What remains after this scouring process, or what oozes from the band before it has set, spreads over the sides of the nest in a thin layer of bubbles so fine that they cannot be distinguished without the aid of a lens.
We often see a torrent of muddy water, full of clay in suspension, covered with great streaks and masses of foam.