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.