156 



MEDICAL ENTOMOLOGY 



with either biting jaws or rudimentary mouth 

 parts ; in the latter case they have thirteen 

 segments and are perineustic. 



Brachycera. Antennae very variable in structure, the two basal 

 segments, as a rule, differentiated from the 

 third, which varies much in shape and struc- 

 ture ; it may be annulated or not ; the arista 

 is rarely dorsal, usually terminal. The vena- 

 tion is complex, more so than that in the 

 Nematocera. Larva with a rudimentary mouth, 

 and either metapneustic or perineustic. 



CYCLORRAPHA. Larva without a differentiated head. Pupa al- 



ways enclosed in the larval skin the puparium 

 the imago escaping through a circular orifice 

 at the anterior end. Frontal lunule present, 

 usually with a ptilinum. 



Aschiza. Antenna as a rule not composed of more than 



three segments, the third with a non-terminal 

 arista. This group contains the three families 

 Pipunculidae, Syrphidae and Platypezidae, in 

 which the frontal suture is wanting. 



Schizophora. The antenna consists of three joints with an 

 arista; frontal suture always present. The 

 larva has no distinct head, and is always 

 amphipneustic. This group is often divided 

 into the Calypterae, in which the squamae 

 are well developed, and the thorax has a well 

 marked transverse suture ; and the Acalypt- 

 erae, in which the squamae are always small, 

 and the thorax is without a complete trans- 

 verse suture. These subdivisions correspond 

 in the main to the Schizometopa and Holo- 

 metopa of Brauer. The former is divided by 

 some into the Anthomyiodia and the Muscoidea. 



PUPIPARA. Parasitic forms, often wingless or dropping their 



wings. Larvae born when ready to pupate. 

 Very aberrant Diptera. 



In this and the following chapter the families which contain im- 

 portant species will be particularly dealt with. For a more general 

 account of the Diptera the reader should consult the Cambridge 



