JOURNAL 



J}f\a Soph 6|nknioIogiraI jStoriFl^g. 



VolT X3L SEPTEM JBER," 1 91 2^ No. 3. 



DIPTERA AT HOME ON SPIDERS' WEBS. 



By Frederick Knab, 

 Washington, D. C. 



Spiders are generally considered very efficient enemies of Diptera 

 and in truth one frequently finds flies entangled in spider webs. 

 Much has been made of the effectiveness of spider webs in the re- 

 duction of mosquitoes and one frequently finds expressions of the 

 most emphatic kind, by economic writers, concerning the usefulness 

 of spiders. I need only call attention to the writings of McCook, 

 John B. Smith and Leon (Roumania). If, however, one searches 

 for accurate observations in support of these statements one finds 

 little more than generalities. In fact species of Diptera belonging 

 to several families of Nemocera have been observed resting un- 

 harmed upon spider webs and evidently select this peculiar habitat 

 for repose. 



At the meeting of the Entomological Society of Washington on 

 July 6, 191 1, Mr. W. L. McAtee presented an observation which 

 showed that at least some species of mosquitoes do not come to grief 

 in spider webs. He found a large number of Anopheles qitadri- 

 maculatiis sitting on a spider web in a hollow tree. They did not 

 stick to the web and on being disturbed they took wing without diffi- 

 culty. Further observation showed that these mosquitoes returned 

 after having taken flight and were perfectly at home on the web.* 

 Since then I have come upon a record of another similar observa- 



* Proc. Ent. Soc. Wash., Vol. 13, p. 193 (1911). 



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