ENTOMOLOGICAL SOCIETY, 



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often be led to predict a serious outbreak. But at the opportune moment, Presto ! a 

 change ! and the species that was but yesterday, as it were, literally swarming, is now re- 

 duced to a minimum, while the dead are everywhere thickly scattered about. Two 

 instances of this sort have, the present year, come under my own observation. Early in 

 May, the females of the grain aphis, Siphonophora avenoe, appeared on the growing wheat 

 and were soon surrounded by their young. These insects were in a short time as plenti- 

 ful as they usually are, at that season, in years of excessive abundance, and there seemed 

 every indication of an outbreak of the pest. But now there appeared a little Braconid 

 parasite, Aphidius avenaphis, and within ten days there were few living adults to be 

 found, though the distended, brown bodies of those that had succumbed to their minute 

 enemy were everywhere plentiful. It was as if a Mighty hand had been stretched forth 

 accompanied by the command, Peace ! be still. During August and early September 

 there were great numbers of caterpillars 

 of Spilosoma virginica (Fig. 4, a cater- 

 pillar, b chrysalis, c moth) and to a less 

 degree of Arotia acrcea, in Northern Ohio, 

 and, if they had all developed moths, 

 there would have been much injury caused 

 by the caterpillars next year. But this 

 was not to be, as by September 20th the 

 dead and dying were hanging to weeds, 

 grass and fences, in myriads, having been 

 attacked and killed by a fungous enemy, 

 probably Empusa aulicce, Reich., and 

 neither of these caterpillars will probably 

 be at all abundant with us next year. The 



same phenomenon was noticed in Ohio — «- 



six years ago. F »g- 4 « 



Scattered through our entomological literature, are hundreds of such illustrations of 

 the value of parasites in holding in check tne hordes of destructive insects that occur in 

 this country, and there is hardly a working entomologist who cannot add to these from his 

 own unpublished notes. 



Of our most destructive insect pests nearly all have been brought to this country 

 from abroad. Lack of their natural enemies here, together with the fact that, in many 

 •cases, these introduced pests are not known as such in their native homes, leads us to 



conclude that we, in our importations, have left these 

 enemies behind. The case is much as though we were 

 to import from some foreign country a huge piece of 

 machinery, but on its arrival we find that the balance 

 wheel has been omitted, and in such a case what are we 

 to do 1 Cable back for the missing wheel, or attempt 

 ,to run our machine without a balance wheel ? There 

 are, doubtless, instances where introduced species can 

 not be subdued in this manner, by the importation of 

 their ancient enemies, but, generally speaking, this 

 appears to be the rational method of accomplishing this 

 end. The history of the introduction of the Orange Scale, 

 leery a Purchasi (Fig. 5), from Australia into California, 

 is probably familiar to most, if not all, of those present. 

 The orange industry of the United States and, as was 

 afterwards learned, of other countries also, was threatened 

 with a most destructive enemy to citrus fruits. In Cali- 

 fornia orange groves were being destroyed to such an 

 extent that it looked as though the cultivation of this 

 fruit would have to be abandoned. But a natural enemy of this pest was discovered in 

 Australia and imported, artificially, into this country, and as a result the pest has been 

 subdued, and with us, before it had spread beyond the Pacific coast. Not only this, but 



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Fig. 5. 



