137 



not beeu submitted to sucli environment. The former, when brought 

 into competition with the latter, under such conditions, rapidly out- 

 number them and get the upperhand. 



THE FOOD HABITS OF THE THRIPID-ffi. 



By Herbert Osborn, Ames, Iowa. 



In general the food habits of all the species in any circumscribed group 

 of animals will be found to agree quite closely, and any departure from 

 such unity of habit will furuish interesting, often important, subjects 

 of study. 



In the Thripidce we have a small group of insects remarkably well 

 defined and agreeing so closely iu structural characters that we would 

 expect in them very close uniformity in food habits. Nevertheless, 

 there has been wide difference of opinion upon this point, some believing 

 them to be essentially herbivorous, while others have held for all, or 

 some, of the species a carnivorous diet. 



In the Canadian Entomologist for 1883 (Vol. XV, p. 151), I have pre- 

 sented a brief resume of the American species, with some notes regard- 

 ing food habits. Since then I have made such observations as possible 

 and have also collected testimony from various sources, so that it seems 

 to me possible to present sufficient evidence to warrant a conclusion 

 approximating the truth. 



Without repeating the substance of my paper in the Canadian Ento- 

 mologist, I may state in brief the most important sources of evidence 

 there referred to. 



Mr. Haliday, whose monograph of the European species has been the 

 foundation for all subsequent work, treats them as herbivorous, as does 

 also Westwood in the " Classification." 



In this country Dr. Fitch, Dr. Packard, and Professor Comstock have 

 described species as injurious to plants. 



Mr. Walsh held strongly to the belief that they were carnivorous, and 

 I will here state his arguments in full. In the proceedings of the En- 

 tomological Society of Philadelphia he says : 



On June 8 I noticed a few imagos of a large Thrip in some galls of P. carycefoUce 

 wliicli were at that time full of their normal tenants ; on June 22 I noticed in galls of 

 the same insect on the same trees many red pujise, apparently of the same Thrips, 

 which seems to have sujiplanted or exterminated the Phylloxera', for almost every 

 gall contained six or seven Thripid pupas and but very few Phylloxeras 



In the Proceedings of the Entomological Society of Philadelphia (Vol. 

 Ill, pp. 611-12), he says : 



What is the cause of this phenomenon (the absence of larvse in Cecidomyian galls) 



I can not say with certainty, but I suspect that the egg or the very young larvte of 



the " gall-gnat" is to a great extent destroyed within the gall by being punctured 



and sucked by some insect foe ; and that that foe probably belongs to Thripidae. 



10332— No. 5 2 



