2 BRACHYCERA. 



to the NEMATOCERA ; in other words, I hesitate to abandon the 

 " old-fashioned " classification of NEMATOCERA and BRACHYCERA, 

 pur et simple, with the PUPIPARA as a third group, either of equal 

 rank with the other two or as a subordinate section of the 

 BRACHYCERA. 



The NEMATOCERA and BRACHYCERA are certainly natural 

 divisions, and Osten-Sacken believed that the characters distin- 

 guishing them were of more fundamental importance than those 

 separating the ORTHORRHAPHA and CYCLORRHAPHA ; he regarded 

 them as of equal ordinal rank with the CYCLORRHAPHA. 

 Williston, on the other hand, considers there is " no distinct 

 limitation between the NEMOCERA and BRACHYCERA,"* but, 

 according to Verrall, the shape of the anal cell provides an 

 infallible character in all those cases in which doubt could possibly 

 arise. It is quite evident, however, that these two groups have 

 always been perfectly clear to most dipterologists from the.fact that 

 no dispute has ever arisen as to the group to which any particular 

 family belonged ; whilst, on the other hand, authors are by no 

 means in agreement as to where the ORTHORRHAPHA NEMATOCERA 

 end and the BRACHYCERA, in the restricted sense, begin. How- 

 ever, these questions of biological affinities amongst the higher 

 divisions can only be approached by those possessing an intimate 

 knowledge of all the families, and it Mould be out of place to 

 attempt any discussion of the subject in a work restricted to the 

 consideration of a limited number of families. 



For the purposes of the present work it will be sufficient to 

 give, in abbreviated and slightly modified form, Brauer's divisions 

 of his CYCLORRHAPHA : 



1. Head not flattened, more or less hemispherical, 



placed perpendicularly to longitudinal axis of 

 body; mouth placed below. Eyes always pre- 

 sent. Dorsal and ventral segments of abdomen 

 well developed, the connecting membrane con- 

 cealed. Imagines living; free, non-parasitic .... 2. 

 Head flattened, placed in longitudinal axis of body ; 

 mouth similarly placed, projecting forward. Eyes 

 present or absent. Dorsal and ventral plates of 

 abdomen very small or absent, owing to pre- 

 ponderance of connecting membrane. Imagines 

 parasitic PCPIPARA. 



2. Frontal bladder-seam running round only upper 



side of base of antennae, narrowly surrounding 

 the lunule, the bladder -seam being therefore 

 restricted, the bladder existing or rudimentary. 

 Jowls not separated from the superiucumbeiit 

 cheeks. Anal cell long and pointed 3. 



* Manual N. Amer. Dipt. 3rd ed. p. 59. 



