DIPTERA 847 



a round opening made by pushing off the head-end of it. 

 1098), the cap thus pushed off is often spHt lengthwise, 

 as shown in the figure. The adult flies possess a frontal 

 lunule and except in the first four families a frontal suture, 

 through which the ptilinum is pushed out, when the adult 

 is about to emerge from the puparium. 



The antennae are three-jointed, with a terminal or 

 dorsal arista, rarely with a terminal style; in the Pupipara 

 the antennas are apparently only one- or two- jointed and 

 sometimes lack the arista. The radius is not more than 

 three-branched; cells Mi and M3 are wanting. The 

 empodia are never pulvilliform. 



SERIES I— ASCHIZA* 



Cyclorrhapha without a frontal suture 



In most of the Cyclorrhapha the head end of the puparium is 

 forced off by the expansion of the bladder-like ptilinum, which is 

 pushed out through the frontal suture when the adult is ready to 

 emerge ; but in four families this is not the case, there being no frontal 

 suture present. These families are grouped together as the Series 

 Aschiza. They are the Phoridas, Platypezidas, Pipunculidae, and 

 Syrphidce. 



Family PHORID^ 



The Hump-hacked Flies 



These are minute, dark-colored, usually black flies, which can 

 be easily recognized by their hiunpbacked form, their peculiar an- 

 tenuce, and the peculiar venation of the wings. Certain species are 

 often found running about rapidly on windows, others on fallen 

 leaves. Sometimes they are seen in swarms dancing up and down in 

 the air. Many species measure less than 2 mm. in length, and some 

 less than i mm. 



The head is small ; the thorax large and humped ; and the abdomen 

 rather short. The antennas are three- jointed; but the first segment 

 is exceedingly small, and the second is enclosed in the third, so that 

 they appear as single-jointed. The third segment bears an arista, 

 composed of two short basal segments and a long, usually more or 

 less plumose third segment. The legs are large and strong and well 

 adapted to jumping. The femora, especially of the hind legs are 

 often very stout and flattened. The wings (Fig. 1099) are large, and 

 are furnished with a series of strong veins near the costal border, 

 which extend but a short distance beyond the middle of the wing. 

 From these strong veins from three to five weak ones extend across 

 the wing. 



In the females of some species that live in the nests of ants and 

 termites the wings are absent or very much reduced in size. 



*Aschiza: a (a), without; schizo (<Tx^fw), a cleft. 



