Rearing of Bourletiella pruinosa collected in the Dutch dunes, demonstrated that spermatophora are placed at random without any apparent mating behaviour. The spermatophora do not seem to have any attraction to the females. An aggregational behaviour, which would enhance the meeting of a spermatophore by a female, could not be demonstrated. The spermatophora are exceptionally resistant to dry and hot air for long periods. They are, contrarily, very sensitive to liquid water, but dew seems not to damage them in nature because they are often deposited on strongly absorbent substrates, notably lichens. A strong indication is found of the presence of two generations of this species. Females are not sexually neutralized, but attain their secondary sexual characteristics only gradually. The suggestion is made that females with the genital orifice open, but lacking most secondary sexual traits are not reproductively qualified.