Effects of diapause duration on future reproduction in the cabbage beetle, Colaphellus bowringi:: positive or negative?

Cabbage beetles, Colaphellus bowringi, undergoing an imaginal summer and winter diapause in the soil, show a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25 degrees C with an LD 14 : 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring's performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female.