Experimental studies in insect parasitism - XV. The means of resistance of a parasitoid larva

Abstract

Embryonic larvae of the ichneumon wasp Nemeritis , released from their egg shells before they were 64½ h old, were encapsulated in caterpillars of their usual host, Ephestia . Larvae re­leased after 66 h were not encapsulated. The property of their surface that provides larvae with resistance is therefore acquired between 64½ and 66 h of development at 25°C. Embryonic larvae released before they were 64½ h old, and allowed to develop for 6 h in a hanging drop of Ephestia blood and saline before implantation in a caterpillar, failed to acquire resistance and were encapsulated. The property that endows them with resistance does not reach the surface of larvae from within; it is applied from without. Embryonic larvae susceptible to a defence reaction can be made resistant if they are put for 4½ h in a drop of saline containing fragments of those parts of the adult genital system from which eggs of Nemeritis acquire their resistance. The protective element on the surface of eggs and of first-instar larvae may come from the same source. The bearing of these and other observations on the specificity of insect cellular reactions is discussed.