THE STRUCTURE, FUNCTION, AND POSTEMBRYONIC DEVELOPMENT OF THE MALE AND FEMALE COPULATORY ORGANS OF THE BLACK WIDOW SPIDER LATRODECTUS CURACAVIENSIS (MÜLLER)

Abstract

A comparison of the structure of the male and female pedipalpi shows that the patella, tibia, tarsus, and the pretarsus of the male are modified. The tarsus in the male is represented by a spoon-shaped cymbium, and the pretarsus by a complex, copulatory palpal organ. This organ in the mature male is a "more specialized" type with an internal receptaculum seminis guarded by the subtegulum, tegulum, median apophysis, radix, terminal apophysis, conductor, and the embolus. The walls of the fundus and the reservoir are of uniform thickness, containing numerous pores on the side facing the gland cells. The ectodistal tooth of the cymbium fits into the socket of the median apophysis, the embolic tip rests on the conductor, and the embolic base is hooked to the basal tooth of the radix. A trigger-like mechanism of extension of the palpal organ is described.The palpal organ arises from the hypodermal cells of the claw fundament. A longitudinal invagination in the ventral lobe of the fundament forms the receptaculum seminis and the dorsal lobes form the accessory sclerites. After transformation of its fundament, the new claw loses connection with the muscle tendons and is short and simple. There is no correlation between the teeth of the claw and the sclerites of the organ.The female copulatory organs consist of paired, dumb-bell-shaped spermathecae; coiled sac-like bursae copulatrices; small, straight fertilization tubes; and blind canals. Ventrally the apparatus is covered by a heavily sclerotized epigynum with an elliptical opening into the atrium which contains the outer openings of the bursae copulatrices. The embolus penetrates the bursa to bring its tip partly within the spermatheca where the broken embolic fragment is later found.The female apparatus arises as a pair of double invaginations of the body wall within the epigastric furrow, immediately ventrad of the opening of the uterus. In successive stages, gradual development of the tissue brings the invaginations outside the epigastric furrow. The two pockets of the invaginations increase in size, the dorsal ones developing into the spermathecae and the ventral ones into the bursae copulatrices.