On the Bionomics and Development of Lygocerus testaceimanus, Kieffer, and Lygocerus cameroni, Kieffer (Proctotrypoidea-Ceraphronidae), parasites of Aphidius (Braconidae)

Abstract

ABSTRACT 1. Lygocerus testaccimanus, Kieff. is a hyperparasite of A p h i s saliceti, Kalt., through the primary parasite, Aphidius salicis, Hal. ; and L. earneroni, Kieff. is similarly a hyperparasite of Macrosiphum u r t i c a e, Kalt., through the primary parasite, Aphidius c r v i, Hal. 2. The Aphidius is attacked immediately before or after metamorphosis, when lying within the empty skin of the aphis within which it is reared. 3. The egg is laid, and post-embryonic development takes, place, outside the body of the host. 4. The evidence points to the conclusion that there are four larval instars and three moults. 5. The larvae differ in several particulars from those of the families of Proctotrypoidea previously described, and there is considerable difference in form between the early and later instars. 6. During development, which lasts about six days, the larva devours its host, and then pupates within the skin of the aphis for a further period of two weeks. 7. Two, and possibly more, broods are reared in the season ; and it is probable that the hyperparasite is a considerable check on the Asphidius in its control of plant-lice infestation. 8. Lygocerus, though occasionally attacked by its own species, was never found to be parasitised by another hymen-opteron. This immunity is probably due to the active movements with which the larva and pupa in the cocoon respond to external stimuli.