Variation in host use and flight ability in the cotton aphid Aphis gossypii Glover is such that some biotypes can
be regarded as cotton-specialized，cucurbits-specialized，migratory and sedentary． However，it is not known whether
cotton-specialized and cucurbits-specialized biotypes，or migratory ( M) and sedentary ( S) biotypes，interbreed． The
sexual forms of cotton-specialized，cucurbits-specialized，migratory，and sedentary biotypes were induced under reduced
temperature and short photoperiod and their mating behavior was investigated． The results indicate that migratory and
sedentary biotypes interbred，and the number of males that completed copulation within three hours did not significantly
differ between inter-biotype and intra-biotype mating． However，it took significantly longer for males to find a mate of
another biotype than one of their own biotype． The duration of copulation of M♀ × S♂ was also significantly longer than
that of M♀ × M♂ and S♀ × M♂ ． Mating was more likely to occur when the male and female were of the same biotype
than when they were from different biotypes． There was a trend towards assortative mating between migratory and sedentary
biotypes． Interbreeding occurred between cotton-specialized (Co) and cucurbits-specialized (Cu) biotypes，and the time
required for males to find a mate and complete copulation were similar between Co♀ × Cu♂ cross and Cu♀ × Co♂
cross．