401 



I have the immature stages of only two genera in my material, and 

 to attempt a generalization of the family and a presentation of the 

 characters for their separation from Dolichopodidae, with which I 

 am almost unacquainted, is impossible. 



Imago. — See family key. 



HABITS OF IvARVAE 



The European species are much better known than the American, 

 and from data supplied by workers on that continent, and from my 

 personal observations, it is evident that the larvae are for the most 

 part either predaceous or scavengers, living in the ground or in wood 

 in a more or less advanced stage of decay. Some species are aquatic 

 or semiaquatic. 



. HABITS OF IMAGINES 



The imagines are in the great majority of cases predaceous, feed- 

 ing upon other insects and occasionally attacking species of the same 

 family or individuals of the same species. There are published 

 records that the male of some genera catches the prey which serves 

 as a meal for the female during copulation. The sexes of Tachydromia 

 and allied genera catch their own prey, usually while running on tree- 

 trunks. Many species have a habit of flying in swarms, remaining 

 in one place and flying with an up and down movement similar to 

 that adopted by certain Chironomidae. Terrestrial species usually 

 fly in this manner on the leeward side of a tree, bush, or other shelter- 

 ing object; but the aquatic forms and those living in damp earth per- 

 form their aerial dance over the surface of a pool in a stream, or over 

 a pond or lake. 



Despite their predaceous habits nearly all genera occur upon flow- 

 ers, sometimes in large numbers. 



•&' 



Rhamphomyia dimidiata Loew 



ffliamphomyia dimidiata Loew, Berl. Ent. Zeitschr., 1861, p. 325. 



Larva. — Length. 7-9 mm. White, head black. General shape 

 musciform, tapered anteriorly, blunt posteriorly. Head when seen 

 from above, as. in Figure 4, Plate LVII; the antennae well developed, 

 2-jointed. Thoracic spiracles small. Abdomen with 8 segments ; 

 circular in cross-section ; segments broader than long, without dis- 

 tinguishable locomotor organs, apical segment rounded; spiracles 

 large, disc-like, separated by a space about equal to width of a spir- 



