The Comstock-Kellogg glands in female Schistocerca gregaria: Their eversion and haemocoelic pressure

The glandular pouches of Comstock and Kellogg on the genital chamber of females of Schistocerca gregaria can be everted and displayed by exerting firm pressure on the tip of the abdomen. The glands evert when the ovipositor values are extended and the gland apertures pass the posterior border of the sub-genital plate. This process has not been observed to occur spontaneously in females in this colony. Increasing the pressure in the haemocoel by means of a saline reservoir is effective in causing gland eversion only when pressures in excess of 75 mm mercury are used: these pressures cause abnormal distortion in the insect. Haemolymph pressure monitored in digging and egg-laying females varies only slightly from atmospheric pressure and never approaches the pressures required to enforce gland eversion. Gland eversion is not observed in digging females, but is difficult to observe in females in the act of laying, due to the presence of egg-pod secretion.These observations are discussed in relation to the structure of the pouches and other information concerning their possible functions in the female desert locust.