1920 ENTOMOLOGICAL SOCIETY. 33 



I 

 It is interesting to note in passing that as the species became less and less 



abundant the environmental pressures became so great that it was threatened 



with extinction. It may also be noted that as the species became rare so did its 



parasites until finally the red-eyed Vireos were averaging a spoil of 198 caterpillars 



from each web. 



When the Webworm had practically disappeared from the entire Province, 

 as represented by nine observation points, something happened that changed tht 

 whole situation. A flight of moths was blown across the Bay of Fundy and the 

 coastal belt from St. John to Moncton was heavily seeded with the insects. 



This condition enabled the species to do battle once more on favorable terms 

 with the Vireos, and it began to increase and spread out again over the Province. 

 It has now spread out over more than half the Province and is gaining ground 

 rapidly. 



The gain in numbers is also greatly favored because the parasites died out 

 as the host became rare and they have not yet returned to the feast. Moreover 

 they are not likely to return until our present outbreak becomes linked up with 

 territory in which they now occur. 



In a word then the causes of our present outbreak are, first an elimination 

 of parasites from Xew Brunswick, then a flight of moths from new territory. 



Having now considered a few insect outbreaks and their causes it may be 

 remarked by way of conclusion that civilization is directly responsible for many 

 of our more notorious outbreaks. We are increasing the food supply of particular 

 insects and thereby making conditions favorable for outbreaks. This is not only 

 true for the insects attacking agricultural crops but is also true for some of our 

 forest insects. In ISTew Brunswick we now have many square miles of forest lands 

 supporting pure stands of poplar and these areas are the nursing grounds of our 

 all too numerous forest tent caterpillar outbreaks. The pure stands of poplar 

 have come in after the fires of civilization have swept away the ancient mixed 

 growth. We also have many square miles of forest now composed of pure stands 

 of balsam fir. In these stands has been nursed the present outbreak of Spruce 

 Budworm — an outbreak that has swept away about three-fourths of the entire crop 

 of merchantable fir in the Province. The overproduction of fir, as already pointed 

 out, is a direct and necessary result of the existing methods of lunibering. In 

 tbo cases of the Forest Tent insect and the Spruce Budworm civilization has had 

 the effect of removing one of the most powerful of the restraining bonds, namely, 

 that which under natural conditions constitutes a food pressure. 



FURTHEE NOTES ON THE CONTROL OF PEAR PSYLLA. 



W. A. Ross AND W. RoBiKSON, Dominion Entomological Labokatory. 

 ViNELAND Station, Ontario. 



With a view of securing some definite data on the susceptibility to common 

 contact insecticides of pear psylla eggs at different stages of incubation, and in 

 order to ascertain what spray material is the most effective ovicide, the following 

 preliminary experiments were conducted this past year (1919). 



Experiments Under Greenhouse Conditions. 



During the latter part of the winter adult psyllas were taken from their 

 hibernating quarters in the orchards and were brought into the greenhouse. There 



3 E.S. # 



