Influence of male presence on clutch size in Schistocerca vaga Scudder (Orthoptera: Acrididae)

Male Schistocerca vaga produce a pheromonal factor that causes increase in clutch size. Females exposed to males, but prevented from physically contacting or copulating with them, produce significantly more eggs (P < 0.01) than virgins not exposed to any males at all. There is no significant difference between the clutch sizes of such exposed females and those of females which are allowed both physical contact and copulation. Castration does not abolish this effect of male presence on clutch size. Visual exposure alone does not enhance clutch size, whereas olfactory exposure, with or without concomitant physical contact, leads to increased clutch size.     

Mechanisms of sperm release from the receptaculum seminis of Schistocerca vaga Scudder (Orthoptera: Acrididae)

Release of spermatozoa from the receptaculum seminis of Schistocerca vaga was studied by means of electrical and mechanical stimulation. Electrical stimulation of the receptaculum nerve, or the ductus aperture nerve, leads to release of spermatozoa from the receptaculum seminis, provided the spermathecal innervation is intact. Mechanical stimulation of the ductus aperture in the genital chamber also leads to sperm release, provided the neural loop, ductus aperture/terminal abdominal ganglion/receptaculum seminis, has not been interrupted at any point. Ten somata in the terminal abdominal ganglion, including 6 dorsal unpaired medial (DUM) neurons, innervate the receptaculum seminis; some of these somata may be neurosecretory. Approximately 80 presumed sensory axons run from the ductus aperture to the same ganglion. On the basis of these neuroanatomical data and the results of electrical and mechanical stimulation, a schema of how the release mechanisms operate in S. vaga is proposed.