THORAX. 



but they rarely take on an extraordinary development. 

 One or the other or both ma}' be greatly elongated (see 

 fig. 19, Bombyliidae), or one or the other may be greatly 

 swollen (see Therevidse). The third joint, however, 

 has in some cases assumed most marvelous shapes, as 

 among the Stratiomyiclse (Neochauna), or Tachinidae 

 ( Talarocera, figs. 6, 7, Schizotachina, Dichocera, etc.) 



Fig. 7. Talarocera nigripauiis, male and female antennae, from the 



side, much enlarged. 



Often the arista has short hairs fringing the upper 

 and lower sides, in which cases it is called pubescent 

 (fig. 5, 5); when the hairs are longer and more feather- 

 like (fig. 5, 6), the arista is said to be plumose; or, if the 

 hairs are fewer and stronger and confined to one side, 

 pectinated. The pubescence or plumosity is almost always 

 more marked on the upper side of the arista; the pecti- 

 nation is very rarely on the under side (Ommatius^ Asi- 



lidse). 



THORAX. 



The thorax is composed, as in other insects, of three 

 parts, the //^-thorax, the meso-ihora.^ and the meta- 

 thorax, but the first and the last are so aborted as to pre- 

 sent but few anatomical characters. The prothorax is 

 perhaps most readily distinguishable in the nematocer- 

 ous flies, forming a rounded collar back of the neck. The 



