HYPERPARA8ITI8M 399 



which had been introduced at an earlier date and without adequate 

 knowledge of its host-relationships. This same hyperparasite 

 also attacks Scutellista cyanea, and there seems little doubt that 

 its activities constitute a most serious inhibitory factor in the 

 achievement of adequate biological control over the scale insect 

 in question. Although due care may be exercised in the exclusion 

 of hyperparasites when parasite introductions are made, it is 

 obviously impossible to guard against the contingency of sub- 

 sequent attacks by indigenous secondary parasites, as has 

 happened with certain of the parasites of the gipsy moth after 

 their introduction into the United States. 



In the Hawaiian Islands the earlier attempts to control the 

 sugar cane leafhopper involved the introduction of various species 

 of Dryinidae. These introductions proved unsuccessful partly 

 owing to the prevalence of hyperparasites. Some of the latter 

 were probably native species which, owing to their minute size, 

 had previously remained undetected, while others were chance 

 immigrants brought in from the United States. It is noteworthy 

 that in England the common earwig Forficula auricularia (L.) is 

 feebly parasitised by the Tachinid Digonochceta setipennis ; 

 observations conducted by A. M. Altson on earwigs collected 

 from various localities failed to reveal more than a 7 per cent, 

 parasitism. At the same time the Digonochceta is subject to attack 

 by the Chalcid Dibrachys cavus {b ouche anus Hatz.) and by the 

 Ichneumon Phygadeuon scaposus Thoms. In attempts to establish 

 this Tachinid in New Zealand in the expectation that in a new 

 and favourable environment it may prove a more efficient element 

 in earwig control, it is important that these hyperparasites be 

 excluded, since they are unknown in that country. On the other 

 hand, it is problematical whether the exclusion of the Dibrachys 

 from consignments of the Tachinid which have been introduced 

 for earwig control into the Pacific side of North America will result 

 in any advantage for the reason that the hyperparasite is already 

 widely distributed over that continent. 



Proper (1934) is one of the most recent writers who discusses 

 the subject of hyperparasitism from a considerable body of 

 evidence. In dealing with the secondary parasites of certain 



