biology of chrysocharis pentheus, an endoparasitoid wasp of the citrus leafminer phyllocnistis citrella stainton

the biology of chrysocharis pentheus (walker) (hymenoptera: eulophidae), the most abundant endoparasitoid of phyllocnistis citrella stainton (lepidoptera: gracillariidae) in ehime prefecture, japan, was studied under laboratory and field conditions. the mean immature developmental time and adult longevity at different temperatures (22 to 31°c) under 50-70% rh decreased as the temperature increased, and females survived longer than males. the developmental threshold of male and female was 8.9°c and 11.9°c, respectively. the effective accumulative temperature (thermal constant) for males and females from egg to adult was 181.8 and 238.1 degree-days, respectively. c. pentheus appeared to be a synovigenic species. the offspring sex ratio from females provided with males was 73.8% males and 26.2% females. presumably, mated females began oviposition 1-2 days after emergence and continued for up to 40 days. females laid a mean of 118.2±10.10 eggs each, and their longevity reached 32.3±0.30 days at 27±1°c, 50-70% rh. the intrinsic rate of natural increase (rm) was 0.144. host feeding or stinging without oviposition killed 65.7±8.65 p. citrella larvae per female. oviposition in the field was highest (62.7%) on the third instar larva of p. citrella, with the rest on the prepupal stage (37.3%), showing a significant preference for third instars. the sex ratio (m:f) of c. pentheus reared from the third instar larvae of host and pupae was 3.3:1.0 and 1.0:3.0 respectively.