The Sexual Behaviour of the Blowfly, Protophormia Terrae-Novae R. -D

Abstract

AbstractIn P. terrae-novae the male courtship behaviour begins with a run towards the female followed by mounting, orientation, and copulation. Male sexual activity begins on the second day after adult emergence if supplied with a solution of "Marmite" yeast extract and milk, sugar, and water. No reactions to a volatile sex attractant could be demonstrated from either sex. Other males are equally effective as females in eliciting "encounters" from sexually active males, and the encounter rate of males in isolated all male cultures is the same as that of males in the presence of attractive females. Though attractive females do not affect the male behaviour before contact they elicit an increased chance of completion of the pattern after encounter, whereas bouts with other males tend to break off in the early stages of courtship. Sexual behaviour directed towards newly emerged individuals of either sex is inhibited relative to that directed towards other sexually active males. The males from mixed-sex cultures gradually become attractive to other males, which respond to them as if they were attractive females. This may be due to their contamination with a female pheromone of the "mounting stimulant" type. Though males fed only on sugar and water showed a vastly reduced rate of sexual activity, their mechanism of sex discrimination remained unimpaired. In cultures with active males, newly emerged females become attractive and mate on the second day after adult emergence. About 4% of the attacks by males on pairs in copula result in a clnange of copulating male. After copulation females reject any further attention from males by horizontal vibration of their wings across the abdomen. This reduces the duration of mounting and prevents genital contact, otherwise mated females are as attractive as virgins. The female vibration response is elicited mainly on mounting, especially after orientation, but never before contact by the male. Males reject courtship with a "pushing" of the hind legs as in cleaning. This operates when a mount persists, and though the chances of orientation and genital extension are reduced the chance of mounting is not.