12 BRACHYCERA. 



earlier families of the BRACHYCERA (STRATJ.OMYID.E, TABANIIWE, 

 some LEPTHLE, etc.) the third joint is usually anuulated, that is, 

 faintly separated by more or less distinctly impressed lines into 

 several divisions, generally eight or five, and in this character 

 considerable resemblance is apparent to the nematocerous families 

 BIBIONID^E, SiMULiiDJE, and liiiYPHiD^. These annulations in 

 subsequent familes of BIIACHYCERA gradually disappear in an 

 obviously single elongate joint, as in many BOMBYLIID^;, THERE- 

 TID^E, and ASILIDJE, with or without a more or less distinct one- 

 or two-jointed apical style ; and in later families still, the 3rd 

 joint is further shortened and may bear either a style or arista. 



The arista, the bristle-like hair situated on the upper side of 

 the 3rd joint, makes its appearance in the very first brachycerous 

 family, the STRATIOMYID^,* and is present in one or more genera 

 in probably all the subsequent families, with a few exceptions 



(TABANIDjE, ACANTIIOMERIUJE, SCENOPJUSTD^, MYDAIDjK, and APIO- 



CEKIUM), and of these, all except the first are groups of quite 

 limited extent. The arista is at first (STRATIOMYID./E, LEPTID^E) 

 mainly apical or subapical, afterwards either apical or dorsal in 

 the same family, and, finally, mainly dorsal (DOLICKOPOUID.E), which 

 is its normal nature in the remaining brachycerous families and 

 in the CYCLORRHAPHA. The arista may be quite bare, pubescent to 

 a varying degree, or conspicuously plumose. In the great majority 

 of BRACHYOERA the two basal antennal joints are differentiated 

 from the 3rd in the na.ture of the scapal joints in NEMATOCERA, and 

 are usually short, bearing short bristles, cylindrical or, especially 

 the 2nd, more or less cup-shaped ; but in the 3rd joint the most 

 varied forms exist even in a single family, this being especially the 

 case in the STRATIOMYJD^E, BOMBYLIIDJE, and SYRPHIDJE. Briefly, 

 the 3rd joint may be elongate-cylindrical (annulated or not), strap- 

 shaped, filiform, tapering, conical, tooth-shaped, oblong, rounded, 

 oval, renit'orm, globular, or of irregular shape. In one aberrant 

 genus (llhachicerus in LEPTID.E) it is strikingly pectinate, recalling 

 Pstlliopliora in the NEMATOCERA, whilst in Talnrocera, a genus 

 of North American Tachinids, the 3rd joint in the female is 

 of an extraordinarily fantastic shape. In the CYCLORRHAPIIA the 

 two basal joints are normally as in the BRACIIYCERA, though 

 the 3rd joint again shows the same extreme range of variety in the 

 two largest families, SYRPHID.E and MUSCID^E, but remains of 

 remarkably uniform, though peculiarly characteristic, form in 

 others (PIPUNCULIDJE, PLATYPEZIDJEJ. In these groups it may 

 bear a short style or an arista. The 1st and 2nd antennal joints 

 sometimes depart from their more or less general form, the 

 former being exceedingly long and cylindrical in Systropus and 

 conspicuously so in Stmtiomyia, the 2nd showing unusual develop- 

 ment in certain genera. 



Coming to venation, it will be observed that in the BRACHYCERA 



* The only nematocerous family in which the arista appears is the OUPIINE- 

 piiiLiD.E, a group of about hall' a dozen species, and as it consists of several 

 joints it is perhaps not truly identical. 



