B. C. ENTOMOLOGICAL PROCEEDINGS, 1912. 35 



The parasites have thus destroyed their food supply, and as they them- 

 selves are often subject to parasitism, their own numbers will be greatly 

 reduced. The pest insect will then breed up ahead of its parasites and 

 we eventually have another epidemic. The fact that secondary parasites 

 are not uncommon and that tertiary and even quaternary parasitism 

 may sometimes occur greatly complicates this whole process. On the 

 average, however, a balance will be struck between host and parasite, 

 the former never reaching such numbers as to destroy its food supply, 

 and the latter never increasing so rapidly as to exterminate its host. 



The utilization of parasites in insect control is a new and promising 

 field in economic entomology. The signal success attending the intro- 

 duction of the Australian Lady Bird Beetle into California, where it 

 succeeded in checking the ravages of the dreaded fluted scale {Icerya 

 purchasi), and a like happy result from the introduction of the same 

 parasite into several other countries, gave a great impetus to this work. 

 A determined attempt has been made by the United States Department 

 of Agriculture and the different State legislatures concerned, to intro- 

 duce and establish European parasites of the Gypsy and Brown Tail 

 Moths. Though many parasites of these pests have been successfully 

 introduced and much valuable work accomplished, the same degree of 

 success has not been attained as was the case in the instance already 

 cited. It was, of course, scarcely to be hoped that one specific parasite 

 could be found that would be as efficient for these highly specialized 

 insects as was the novius against the fluted scale. The reasons for 

 this, as pointed out by Dr. L. O. Howard in his bulletin on the subject, 

 are plain. The novius is an active insect, crawling actively as a larva 

 and capable of flying from place to place as an adult. It is a very 

 rapid breeder, having at least two generations to every one of the host. 

 It feeds upon the eggs of its hosts, and, strange to say, it seems to have 

 no parasites of its own. Its host, on the other hand, except when newly 

 hatched, is entirely motionless and has no means of escaping or of 

 defending itself against its enemy. These are things which do not hold 

 good in very many cases and consequently it was hardly to be expected 

 that such immediate results could be obtained. Those engaged in the 

 work are convinced that the desired result will be attained when they 

 have secured a sequence of parasites, of egg, larva, and pupa ; and of 

 forms differing among themselves in life history and method of attack, 

 all working harmoniously together towards the same end. 



The whole subject of insect parasitism, however, is so large that 

 to discuss it any further in a paper of this general character would be 

 out of place and would take up altogether too much time. I will there- 

 fore proceed to the next topic. 



