Temperature requirements of some aphids and their parasites.
The temperature requirements of five aphid species (Acyrthosiphon pisum (Harris), Aphis craccivora Koch, Brevicoryne brassicae(L.). Macrosiphum avenae (F.) and Masonaphis maxima (Mason)) are shown to differ from place to place for the same species and from species to species. The temperature requirements of the parasites (six, including Diaeretiella rapae (M'Intosh), Praon pequodorum Vier. and Aphidius spp.) and hyperparasites (two) associated with these aphids have been found to differ in a similar manner but, as a rule, are higher than those of their hosts. It is suggested that a thermal constant higher for the parasite than for the host is advantageous to the parasite.