Site of water vapor absorption in the desert cockroach, Arenivaga investigata.

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Abstract
The desert cockroach A. investigata, can gain weight by absorption of water vapor from unsaturated atmospheres > 82.5% relative humidity. Blocking the anus or the dorsal surface with wax does not prevent water vapor uptake, but interference with movements of the mouthparts or blocking the mouth with wax prevents uptake. Weight gains are associated with the protrusion from the mouth of 2 bladder-like extensions of the hypopharynx. During absorption these structures are warmer than the surrounding mouthparts, their surface temperature increasing with relative humidity. The surfaces of the bladder-like structures probably function at least as sites for condensation of water vapor, but the precise location of its transfer into the hemolymph was not identified.