Lygocoris pabulinusfemales are polyandrous under laboratory conditions (Groot et al., 1998). As the insect mating system affects sexual communication and thus sexual behavior as a whole, we studied sperm transfer, storage and displacement inL. pabulinus.To be able to fully understand these processes, detailed information on the female reproductive tract is essential. Therefore, we first studied the female genitalia in detail. The bursa copulatrix consists of four plates, and a spermatheca is connected anteriorly to the bursa. At copulation a spermatophore is formed in the spermatheca. The spermatophore is compartmentalized, consisting of a sperm-containing portion, a large sperm-free portion and a mating plug. After 24 h the spermatophore has partially disintegrated. The mating plug is still intact but reduced in size. Sperm are found throughout the spermatheca and in the median and lateral oviducts where fertilization most likely takes place. The amount of male-derived substances transferred to females during first matings was ca. 5.2% relative to male body weight. To understand the effects of matings on the sexual communication, we determined sexual attraction of mated females at long and close range. At long range females were unattractive for only 1–2 h after mating, while they remained attractive at close range. Mated males were not attracted to virgin females for 2 h after mating, and only 23% of the tested males mated again within 24h. Together, these results suggested a high paternal investment that may affect reproductive output. To determine if this is the case, and hence if multiple matings affect fecundity and/or longevity, we conducted two oviposition experiments. From these experiments no positive effects on total fecundity or longevity in multiply mated females were apparent.