Females ofSinella curviseta(Collembola: Entomobryidae) were shown to produce 2 stimuli that increase the deposition of stalked spermatophores by males. One stimulus, the instar stimulus, is associated only with females in reproductive instars. The second, the position stimulus, increases spermatophore deposition in the brief interval preceding and coinciding with the female's receptive period within the reproductive instar. Further investigation determined that the position stimulus is a volatile pheromone.