Diuretic Function of the Labial Glands in Adult Giant Silk Moths, Hyalophora cecropia

Abstract

DURING experiments on the water balance of pupal and mature Hyalophora cecropia (Schneider), it was observed that the facial area of the adult may become moist when the hæmolymph is diluted. A similar, but spontaneous, discharge occurs when the adult is emerging, the watery exudate serving to soften the stiff matted silk of the emergence tunnel by which they escape from the cocoon. The fluid is released from labial glands which open through a medial pore situated on the labium between the rudimentary galeæ. These glands, which secrete silk in the larva, survive metamorphosis to the non-feeding adult as a pair of tubes composed of a thick-walled posterior part lying ventrally in the prothorax and a thin-walled, much folded anterior part which unites with its counterpart and opens at the labial pore. The present experiments show that these glands not only persist, but also continue to secrete in the adult, where they become organs of diuresis. This work records the relationship of secretion to physical restraint, and the high rates of secretion caused by dilution of the hæmolymph.