324 PARASITISM 



Since the Apanteles attacks only very young caterpillars, and the 

 other parasites do not, it is only subject to competition in its 

 later instars — when it is most likely to prove the survivor. Pimpla, 

 on the other hand, attacks only pupae, and for that reason is 

 largely out of range of severe competition. 



Another noteworthy example is instanced by Muesebeck (1918) 

 in his studies of the parasites of the brown-tail moth {Euproctis 

 chrysorrhosa L.). As a result of the dissections of over 13,000 

 host caterpillars it was found that whenever larvae of the Braconid 

 Apanteles lacteicolor enter into competition with those of Meteorus 

 versicolor Wesm. or of the Tachinid Zygobothria nidicola Town., 

 or with both species, these latter are killed, evidently as the result 

 of some toxic secretion induced by the Apanteles. 



2. Multiparasitism without parasite mortality. This phase is 

 probably by no means infrequent, especially with regard to the 

 parasites of Lepidopterous larvae and of the Lecaniine scale-insects. 

 In the case of Coccus caprece of the hawthorn, multiparasitism is 

 a common event, the parasites involved being the Chalcids 

 Blastothrix sericea (hritannicd) and Aphycus punctipes (melano- 

 stomatus). In localities in Britain where these two parasites are 

 abundant, a dozen or more examples of both species may sometimes 

 be reared from the same individual host. Pierce mentions an 

 instance among weevil parasites in which nine examples belonging 

 to two species of Aphiochceta were reared from a single host, and 

 cases where two species of ectoparasites were reared under similar 

 circumstances. 



The effects of the competition upon the insects concerned are 

 usually in proportion to the numbers present. The most obvious 

 result is the development of individuals stunted or reduced in size, 

 and according to Fiske material reduction in their reproductive 

 capacity is also common. 



3. Multiparasitism involving the death of the parasites. 

 Instances of this kind have been seldom recorded, but it appears 

 that the fatal consequences are the result of exhaustion of the 

 food-supply or of the premature death of the host. In his study 

 of the parasites of the white-marked tussock moth L. O. Howard 

 states that, when the Ichneumon Pimpla inquisitor oviposits in 



