38 INTRODUCTION. 



The subject of the higher systematic subdivisions of the Diptera 

 has never received from me any special study, so that, perhaps, 

 opinions on it are out of place, but I have always considered the 

 NEMATOCEHA and BRACHYCERA (by which latter I mean all the 

 remaining families except the EPROBOSCIDEA) as a more natural 

 classification of the perfect insects than the shutting off of the 

 SYRPHID.E and allied families from the present-day " BRACHYCERA," 

 and allying them to the Muscids in a common group, opposed to 

 the NEHATOCERA and present-day " BRACHYCERA " combined. 



If the ORTHORRHAPHA and CYCLORHHAPHA are recognised as 

 the primary divisions, it seems to me that the secondary divisions 

 might be called NEMATOCERA and ORTHOBRACHYCERA, in the 

 ORTHORRHAPHA; and CYCLOBRACHYCERA, MUSCOIDEA ( = Mus- 

 CID^E, sensu lato, plus PHORID^E) and EPROBOSCIDEA (.or PUPIPARA), 

 in the CYCLORRHAPHA. 



I cannot help feeling instinctively that the most natural 

 classification is into'two suborders. NEMATOCERA and BRACHYCERA, 

 the latter divided into two groups, the first containing all the 

 families except the MUSCIDS * and PHORID^E, which together 

 would form the second group. The PUPIPARA might either form 

 a third group of the BRACHYCERA or constitute a third suborder. 

 In other words, it seems unnatural to me to separate the 

 SYRPHIDJE, PIPUNCULID^E and PLATYPEZID^E from the families 

 forming the present-day BRACHYCERA. The MUSCIDS as a whole 

 seem to form a very compact, homogeneous group, quite different in 

 external structure, appearance, and habits from the other Brachy- 

 cerous families, and possessing a typical venation. The aberrant 

 family PHORID^ seems most nearly allied to the MUSCIDS, through 

 the BORBORIN^; or some allied group. The unfortunate part of 

 the primary classification (though possibly biologically correct) 

 into ORTHORRHAPHA and CYCLORRHAPHA is that that system 

 affords no easy clue to the determination of the perfect insect s, 

 since the absence or presence of the frontal lunule is the only 

 character offered and this moreover is either absent or incon- 

 spicuous in three families of CYCLORRHAPHA in which it should be 

 present, including the extensive family SYRPHID^E. Since be- 

 ginners certainly never commence their studies with life-histories, 

 I defy any ordinary entomologist attacking the Diptera as a new 

 study to sort out into their respective suborders a box full of 

 mixed Diptera of mar} families. He would therefore inevitably 

 be compelled to fall back on the old groups of NEMATOCERA and 

 BRACHYCERA, eliminating the SYRPHIDJE, PIPUNCULID^E, PLATY- 

 PEZIDJE, MUSCIDS, PHORID^E and so on, by their respective very 

 typical systems of venation. 



* I am convinced that the whole of the MUSCID^E should be included in a 

 single family and that the Tachinids, Anthomyids and so on should rank but 

 as sub-families, the various Acalyptrate groups each forming a subfamily of 

 equal rank with them. The Dexids and Sarcophagids would be sunk in 

 TACHININ.E, and the intermediate Calyptrate subfamily would be MI'SCIN^E (in 

 the old sense). 



