comparative Chcetotaxy. 513 



Ijleural, the position of which may afford vahiable generic 

 characters. Most of the Calijptrata, except the Antho- 

 myidce, have a tuft or row of bristles on the hypopleura, 

 a region which is destitute of them in the other famihes 

 of Diptera. 



The dorso-central region contains the usual four rows 

 of bristles, more or less complete*; the dorso-humeral 

 region one or several bristles on the humeral callus, two 

 posthumeral, on the prassutural triangular depression, 

 and a few other bristles, inserted in the interval between 

 the humeral callus, the praesutural depression, and the 

 outer row of the dorso-central region; these bristles I 

 have called the intra-Jiumeral bristles. In the Antliomyina 

 there are usually only two such bristles ; one of them 

 seems to be the homologue of the praesutural bristle of 

 the Acalyptrata, and is inserted immediately above the 

 prgesutural depression ; the other is in front of the 

 former, near the humeral callus. In Calliphora erytJtro- 

 cephala, Lucilia Ccesar, efec, I perceive four such bristles 

 that are more conspicuous than the others ; three along 

 the praesutural depression, the fourth near the humeral 

 callus. 



The dorso-alar region contains (usually) two posterior 

 supra-alar bristles, inserted on the post-alar callus ; the 

 second of them, as usual among the Acalyptrata also, is 

 placed immediately above the alar frenuin; and a row of 

 anterior supra-alar bristles, three or more, along the 

 edge of the anterior supra-alar cavity. The other 

 bristles of this region may be called the intra-alar 

 bristles, and form a longitudinal series of two or three, 

 between the supra-alar bristles and the outer row of the 



"-'= The outer row is called by Kowarz, " die inneren Dorsal- 

 borsten" (Die Dipterengatt. Lasiops. iu deu Mittli. d. Milncheuer 

 Vereins, 1880, p. 125, note), because he applies to the Muscidce 

 the terminology adopted by Mik for the DoIicJiojwdidce. But I 

 believe that, in a terminology generally applicable, it will be found 

 much more convenient, even unavoidable, to distinguish the inner 

 and outer pairs of rows of dorso-central bristles. When the inner 

 rows are very much differentiated, as is the case in the Dolichopo- 

 didce, they may be called by the name preposed by Prof. Mik for 

 them — acrostichal bristles. But it must be borne in mind that 

 these bristles represent the inner rows of the dorso-central bristles 

 in a great many Diptera ; and that it is for this reason inconvenient 

 to call "innere dorsal Borsten" that pair of rows which in reality 

 is the outer. This is one of those cases where it seems to me a 

 change in the nomenclature adopted by former authors becomes 

 unavoidable. 



