398 BIOLOGICAL CONTROL 



puparia affected by multiparasitism were attacked by the Opius 

 alone, it is very uncertain whether it would have raised the 

 efficiency of the latter to more than 65 per cent. 



Hyperparasitism. The incidence of secondary parasites attack- 

 ing a primary parasite of an injurious insect has a very definite 

 bearing upon biological control. There is direct evidence that 

 the efficiency of certain introduced parasites has been enormously 

 reduced or even nullified by the activities of secondary parasites. 

 The perplexing and involved problems centred around the inter- 

 relations of hyperparasites and their different hosts have already 

 been alluded to (p. 327), but in illustration of their practical 

 bearing certain concrete examples may be quoted. A primary 

 parasite of one species of insect may function as a secondary 

 parasite of another, as is well exemplified by the Chalcid Mono- 

 dontomerus cereus Walk., which was introduced into the United 

 States in connection with the control of the gipsy and brown-tail 

 moths. Although a primary parasite of the pupge, and especially 

 those of the brown-tail moth, it has also proved to be a secondary 

 parasite. Among imported primary parasites which this species 

 utilises as its hosts are the Braconid Apanteles lacteicolor and the 

 Tachinid Zygobothria nidicola. This dual behaviour has rendered 

 it extremely difficult to determine whether its occurrence as a 

 secondary parasite outbalances its value as a primary agent in 

 control. Another example is afforded by Schedius kuvance How., 

 a valuable egg-parasite of the gipsy moth, introduced from Japan. 

 Later observations have shown that this species also behaves as 

 a secondary parasite, since it occasionally attacks the Braconid 

 Apanteles melanoscelus Ratz. The latter species, it may be added, 

 is a native of Europe, and was also introduced for controlling the 

 gipsy moth. 



A striking example of the importance of hyperparasitism is to 

 be found in California, where the Chalcid Metaphycus lounshuryi 

 was introduced from South Africa for purposes of controlling the 

 black scale of citrus fruits (p. 378). This introduction gave 

 promise at first of an almost complete control of the scale insect 

 in the coastal areas. Gradually, however, its efficiency has 

 become checked by a secondary parasite, Quaylea whittieri (Gir.), 



