Effects of temperature and host on the pre-imaginal development of the parasitoid Diglyphus isaea (Hymenoptera: Eulophidae)

The development of Diglyphus isaea (Walker), a parasitoid of leafminers, was studied under laboratory conditions at four constant temperatures (15, 20, 25, and 30degreesC on the hosts Liriomyza trifolii (Burgess) and Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). Parasitoid developmental time was found to be inversely related to temperature. At 15 degreesC, D. isaea took about 28 days to complete its development on L. huidobrensis and about 27 days on L. trifolii. In comparison, at 20degrees C developmental time dropped to half on both species and the same happened fro m 20 to 30degreesC. At 25degreesC, parasitoid development was complete after about 10 days. At all tested temperatures and on both host species, the length of pupal stage of the parasitoid was slightly shorter than the egg + larva period. Linear regression and the Logan model were used to describe the relationship between developmental rate and temperature. For egg to adult development, female D. isaea required 161.8 degree-days (DD) above the theoretical threshold of 9.2degreesC-on L. trifolii and 165.0 DD above 9.3degreesC on L. huidobrensis,and males required 151.4 DD above 9.5degreesC on L. trifold and 157.4 DD above 9.3degreesC on L. huidobrensis. Optimum temperatures for total female and male development on L. trifolii were 33.3 and 32.3degreesC, and on L. huidobrensis 32.6 and 31.0degreesC, respectively. The effects of host, sex, and temperature on parasitoid size were studied. Significant sex-temperature, host-temperature, and host-sex-temperature interactions were found. The host species was found to affect female parasitoid size differently based on temperature. (C) 2002 Elsevier Science (USA). All rights reserved.