352 



GUIDE ECOLOGY TO FAVOR AGRICULTURE 



The present investigations suggest how far we are from appreciating the 

 abundance and importance of insect parasites and how backward in attempting 

 their control. Howardula is, beyond any reasonable question, ages old, for 

 on no other supposition can the remarkable relationship of host and parasite 

 be explained. It is only one of a consider- 

 able number of parasites of the same destruc- 

 tive insect that have much to do with the 

 welfare of the host. Intelligently increasing 

 the incidence of the parasite will decrease 

 the ravages of the host. When we come to 

 understand these relationships, these "bal- 

 ances" between host and parasites, doubtless 

 we can do much toward inclining the "bal- 

 ance" in our favor. We hear more or less of 

 organisms introduced to new areas without 

 their enemies and parasites, and in conse- 

 quence becoming frightful pests; and we have, 

 very painfully and slowly it seems to some of 

 us, learned that searching for and introduc- 

 ing these same enemies and parasites affords 

 relief. Marked successes of this kind at last 

 place it beyond doubt that this portion of 

 the field of economic parasitology will be Jjf e 8 gru e * d d of *^^ 



Carefully explored. But there is another entering the grub. The sharp active man- 



very important part of the field of which we Jgft?g n ^ u a ld ' eemtaberatherim P ass - 

 hear little if anything, and that is the com- 

 prehension and watchful control of what may be termed indigenous or long- 

 established "balances." 



The cucumber-beetle affords good enough example of these latter to justify 

 an appeal, on the basis of it, to economic biologists to scrutinize more carefully 

 the ever changing "balances" between pests and their parasites and other ene- 

 mies, including pests of long standing, with a view to keeping the "balance" 

 always inclined in our favor. I believe any well trained, experienced and 

 thoughtful biologist will agree that such a course is bound finally to result in 

 notable economies. A case in point is the existence of localities, among those 

 here tested, in which the total zoo-parasitism of the beetles reached only about 

 two per cent. At the same time not very far away there was a nemic infesta- 

 tion exceeding fifty per cent and a dipterous infestation exceeding forty per cent. 

 The investigation showed that the transference by post of the two parasites 

 mentioned from highly infested areas to low or non-infested areas was easily 

 feasible at small cost. Beetles simply posted in a ventilated box containing 

 cucurbit leaves survived a two to four days' journey; turned loose at night 

 they lived. 



