Abstract: To test the “host size-quality hypothesis”, the feeding time of Pieris rapae final instar larvae was manipulated to obtain a wide range of body size (mass) of host pupae, which were then individually exposed to parasitism b y gregarious parasitoid Pteromalus puparum. The offspring number of the para sitoid after a single attack was recorded, and the offspring sex ratio and body size were also observed. The results showed that the offspring production was li nearly increased with increasing host pupa mass at oviposition, being 31497 in dividuals per gram pupa mass on average. The proportion of offspring females and the body size (hind tibia length) of offspring males and females also increased with increasing host pupa mass. The results suggest that P. puparum could allocate its offspring number and sex ratio, so as to maximize its fitness, based on assessment of host pupa mass. The reproductive strategy of P. puparum and related factors were discussed.

Key words: Arundo donax, Phytoremediation, Wetland, Bio-concentration