The Two-winged Flies 



335 



jr other vegetal)le matter, are also probably predaceous, feeding on smaller 

 insects living in the same j)laces. 



The commoner species that dance in large swarms belong to the genera 

 Empis and Rhamphomyia (Fig. 470). The males of certain species of Empis 

 and Hilara have the odd habit of blowing out bubbles of a whitish viscid sub- 

 stance which they carry about with them in the air. It is believed that these 

 toy balloons are attractive to the females. At least, Professor Aldrich, a 

 well-known student of flies, has seen a female choose that male among several 

 which was carrying the largest balloon! 



An attractive lot of small slender flies, usuall\- of iridescent green or 

 greenish-black or blue color, with 

 unusually long slender legs, are 

 the Dolichopodidae, or long-legged 

 flies. They are found especially 

 in marshy or low places where 

 vegetation grows lush and rank. 

 They flit about searching for 

 lesser insects, which they catch 

 and devour. They often get their 



prey by swift chasing over leaves or ground or even on the surface of water. 

 Like the Empidids the larva2 are also predaceous, living underground or in 

 decaying vegetable matter. Some have been found in the exuding sap of 



Fig. 471. — Diagram of wing of dance-fly, 

 Empis sp., showing venation. 



nvrl 



Fig. 472. Fig. 473. 



Fig. 472. — ^Mouth-parts of dance-fly Rhamphomyia sp. lb., labrum; mx., maxilla; 



mx.L, maxillary lobe; vix.p., maxillar\' palpus; /»., labium; hyp., hypophar)'nx. 

 Fig. 473. — Dolichopus lobatus. (Three times natural size.) 



trees and elsewhere on or under bark. The larvae of certain species spin 

 little thin cocoons when ready to pupate, but with most the pupa is 

 naked. 



