146 Journal New York Entomological Society. t^'oi- ^X- 



in shady woods, Jacobson is quoted as follows : " It has the habit to 

 suspend itself with the front legs from spiders' webs; when one of 

 the fore legs are wanting, as frequently happens with these delicate 

 flies, one of the middle legs is utilized. One sometimes sees twenty 

 or more flies close together, suspended from a horizontally stretched 

 spider's thread ; they all bob up and down very rapidly, at the same 

 time swaying to and fro, sometimes in unison and sometimes not. 

 This comical rope-dance is continued for a long time. Because the 

 tips of the legs are white they are very plainly visible, while the 

 spider thread on which the flies hang is generally not visible, it ap- 

 pears as if they danced in the air and touched each other with the 

 tips of their front legs." Doleschall, who first observed this curious 

 dance, did not detect the spider threads, which was perhaps due to 

 the fact that his observations were made inside of houses.^ Jacobson, 

 in the paper quoted above, comments on Doleschall's observation as 

 follows: "If Doleschall describes the flying in a chain without men- 

 tioning the spider thread, this is due to incomplete observation. 

 These Dicranomyias never form chains without being suspended from 

 spider threads. These threads are however sometimes so fine that 

 one can only see them from a definite position (so, for example, 

 that they reflect the sunlight)." 



Except in the case of the chironomid, no good reason is apparent 

 for the presence of the insects on the spider webs. The habit cer- 

 tainly shows some adaptation. Possibly the web serves as a refuge 

 where these insects may rest secure from other insects. Some ex- 

 planation should be sought for the fact that these Diptera can fre- 

 quent the webs without becoming entangled or being preyed upon 

 by the owner. 



NEW GALL MIDGES OR ITONID^ (DIPT.). 



By E. p. Felt, 

 Albany, N. Y. 



Below we describe a number of new western forms received 

 through the kindness of Prof. E. Bethel, Denver, Col., and of Mr. 

 P. H. Timberlake, of the U. S. Bureau of entomology-. 



^ Natuurk. Tijdschr. Nederl. Indie, Vol. 14. p. 390 (1857); quoted by 

 Osten Sacken, Berl. Ent. Zeitschr., Vol. 26, p. 88 (1882). 



