REPORT OP THE STATE ENTOMOLOGIST 1903 131 



It is undoubtedly true that natural enemies, prominent among 

 which are ladybugs, syrphus flies and lacewing flies, serve as very 

 useful checks on this interesting group of insects. Repeated 

 observations in different countries, and extending over a series of 

 years, have demonstrated that these insects multiply enormously 

 during periods when plant lice are unusually abundant, and 

 though it may require some time for the natural enemies to over- 

 take their hosts, this is bound to occur in course of time. 



The attack of 1903 was not only characterized by excessive 

 severity but also by an undue prolongation ; and this latter may 

 have been in part due to unusual rains, which were not favorable 

 to the comparatively unsheltered natural enemies and hindered 

 their gaining an ascendancy over their hosts. The explanation 

 for this is that the plant lice, before the appearance of the rains, 

 had ample opportunity to curl the leaves and therefore provide 

 themselves with shelter from almost any inclement weather. 

 These retreats afforded admirable breeding places from which the 

 insects could emerge and attack adjacent foliage, so that the 

 usual destructive influence of showers would be modified to a 

 considerable extent; on the other hand, the larger predaceous 

 enemies would hardly reap an equal benefit from this protection, 

 and consequently would be delayed in gaining the ascendancy. 



Appletree plant lice (Aphis mali Linn, and others) . These 

 species commonly occur in greater or less numbers throughout 

 the orchards of the State, and their abnormal increase depends 

 on favorable climatic or other conditions. Such was character- 

 istic of the spring and early summer of 1903, and as a result 

 injuries by these species were not only much more marked than 

 usual but also prolonged to a much later date. The worst af- 

 fected trees, which were usually young, presented a very charac- 

 teristic appearance, and the injury was so severe that very little 

 growth was possible. Such a large amount of honeydew was ex- 

 creted that the foliage was almost entirely blackened, and an 

 examination of many trees showed that the growing tips were 

 literally covered by hungry plant lice anxious to reach a tender 

 spot. The severity of the attack began to be evident about the 

 last of May, and was more so in June, continuing in July, and in 



