Diapause in a migrant insect, the milkweed bug Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae).

Oncopeltus fasciatus exhibits a facultative reproductive diapause which is triggered by short photoperiods. The duration of the triggering photoperiod (the "critical photoperiod") is a function of the environmental conditions under which populations are reared. Some individuals are apparently sensitive to critical photoperiods in the early instars, but maximum sensitivity, indicated by 100% diapause, occurs in the late 5th instar during development of the pharate adult. Sixty per cent retain sensitivity into the first five days of adulthood. Temperatures of 27°C can prevent diapause. Once initiated, diapause can be broken either by raising the temperature or increasing the day length; it is broken abruptly, for once oviposition starts, it proceeds at maximum rate. Diapause contributes significantly to a migratory strategy in the temperate parts of the range of O. fasciatus and probably does so in the tropics as well.