Temperature requirements of Aphelinus sp. nr. varipes (Foerster) (Hymenoptera: Aphelinidae) a parasitoid of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae)

The thermal requirements, lower developmental threshold (t) and thermal constant, (K) for three developmental stages of an Aphelinus sp. nr. varipes (Hymenoptera: Aphelinidae), a parasitoid of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae), were established under laboratory conditions. Studies were conducted at constant temperatures across a range from 14-30 C and with a 16L:8D photoperiod. During a preliminary trial with a 12L: 12D photoperiod, diapause was induced at 14C. The thermal requirements for the egg to mummy, mummy to adult and egg to adult development periods were estimated respectively as t = 6.59,8.03 and 7.53 C, and K = 96.71, 111.12 and 212.77 degree-days. The upper developmental threshold was considered to be above 30 C because development did not cease and was not prolonged at this temperature.