Proceedings, 1921. 149 



grounds and distributing centres for insects which may become garden or 

 orchard ])ests. 



In studying man's influence on the flora of the \'ancouver District, 

 one has to obtain a ghnipse of tlie original forest formation as a basis 

 for comparison. Unfortunately, this cannot be seen in any part of Greater 

 \'ancouver, not even in Stanley Park, which bears abundant evidences of 

 the logger's axe. We can tell, however, that the forest was predominantly 

 evergreen, with alder and elder, willows and crab-apple, fringing the forest 

 on boggy lands, and where the soil was too wet for Douglas fir to encroach ; 

 and maples, cherry, and dogwood along the slopes near the Coast. 



In those days it was absolutely impossible to have a tent-caterpillar 

 I>Iague such as we have experienced during the past few years ; there were 

 not sufficient food-plants to support it; the coniferous trees limited the 

 distribution of deciduous species and caused the starvation of millions of 

 seedlings which germinated in the darkness of the evergreen forest. 



With the advent of the logger, open spaces in the forest provided the 

 necessary light for the success of deciduous trees whose seeds were dis- 

 tributed by wind or l)y birds, and some of those early intruders may be 

 found in various parts of Greater \^ancouver as fairly large trees. 



With the establishment and development of the City of Vancouver, 

 and subsequently of the adjacent municipalities, the wholesale clearing of 

 property opened up large areas for the increase of deciduous trees, notably 

 alders and willows, whose seeds are adapted for distribution by wind. The 

 result is to be seen to-day in most parts of Greater Vancouver — and in other 

 Coast districts — where, on much of the " wild land " and some of the 

 " impro-tad land," we see young forests of food-plants for insect pests, 

 replacing the forests which so long served as a natural protection against 

 their invasion. 



Man has thus upset the balance of nature, and if left to herself Nature 

 will gradually restore the former order of things and evergreen trees will 

 again become dominant, because in this locality they constitute what is 

 termed the climax flora. 



As a step towards the rehabilitation of the normal forest, Nature must 

 control the abnormal growth which followed man's overthrow of natural 

 conditions ; the tent-caterpillar is but one of Nature's agents in this work, 

 and, judging by the results of the past few years, it has proved a very 

 efifective one. 



It will therefore be seen that anything done to encourage the growth 

 of certain species of deciduous trees will also encourage the increase of tent- 

 caterpillars ; and conversely, by encouraging evergreen trees and such 

 species of deciduous trees as are not food-plants of the tent-caterpillar, we 

 lessen the risk of future plagues. 



To directly attack the tent-caterpillar by spraying vegetation on vacant 

 lots is contrary to nature and tends to prolong the duration of the plague ; 

 by adopting this method we protect unnatural vegetation to increase the 

 menace every succeeding year. It is better to assist in restoring the balance 



