TAXONOMY OF MUSCOIDEAN FUHS — ToWXSEXD 39 



The Acroceridae, for instance, are to be noted as an extra-cyclor- 

 rhaphous group which has developed very large tegulae, wholly con- 

 cealing the halteres and probably accessory to a highly developed 

 auditory sense in the latter. It seems to be chiefly groups contain- 

 ing a large percentage of endoparasitic forms which are provided 

 with teguke. and it is possible that a greatly increased auditory per- 

 ception is necessary to these forms as an aid to them in the search 

 for and ultimate detection of their hosts. 



The validity of the time-honored separation of the Calypterata and 

 Acalypterata on the characters of the comparative presence or absence 

 of tegulae alone may well be open to serious doubt. The unflexed 

 fourth vein, which from its doubtless far greater age should be a 

 nuich more valid character, would indicate a closer relationship of 

 the Anthomyioidea with the Acalypterata than with the Muscoidea. 

 Yet this does not appear to be the proper and natural grouping. It 

 rather seems preferable to adopt Brauer's names Schizometopa and 

 Holometopa as founded on characters of greater valne than either 

 those afforded by relative development of tegul?e or those of wing 

 venation, and to recognize therefore the Anthomyioidea as a super- 

 family of the Schizometopa. While the result is mainly the same, 

 the divisions become founded on valid rather than on mutable char- 

 acters. The tegul?e have developed, though not uniformly, in the 

 Schizometopa. They have also developed to a certain extent in 

 some of the Holometopa. This fact demonstrates their unfitness for 

 taxonomic use in these divisions. There is a distinction between the 

 characters of a functional organ and the character of the presence 

 or absence of such organ. Moreover, it may be noted that Robineau- 

 Desvoidy's division Calypteratae was applied by him to the super- 

 family Muscoidea of the present paper in the main sense, as is 

 further brought out under the head of Synopses. 



Abdomen. — The number of abdominal sclerites should be of sub- 

 family significance at least, and the form of the abdomen is almost 

 invariably of generic value. 



MacrochcetcE and bristles. — Chsetophorousness in the Diptera finds 

 the climax of its development in the tachinoid stock of the Muscoidea. 

 While chaetophorous characters are, evolutionally, of recent origin, 

 yet the arrangement of the macrochaetae of the head, thorax, abdo- 

 men, and legs becomes highly important in separating tribes, genera, 

 and species. The characters to be derived from the macrocha?ta? of 

 the head rank even higher and serve for the separation of subfamilies 

 in certain cases. In one or two groups, the Gymnosomatinae and 

 Phasiina?, the peculiar chaetotactic characters of the head are cor- 

 related with an absence of macrochaetae on the abdomen, while in cer- 



