10 URACHYCEKA. 



The external characters of the Beacuycera and Cyclorrhapha 

 exhibit as much, if not greater variation than those of the 

 Nematocera. As the introduction to the previous volume on 

 Diptera dealt with characters common to the order generally, 

 those pages may be consulted in conjunction with the present 

 summary, which is couliued to the Bracuycera and those families 

 of the Cyclorriiapiia treated of herein. 



The eyes in the higher BRAcnvcERA and higher Cyclorrhapha 

 are generally contiguous or subcontiguous above in the male, and 

 such flies are said to be holoptic, the eyes in the female being 

 distinctly separated by a comparatively broad frons, but exceptions 

 are numerous. Diptera in which the eyes are well separated in 

 the cT are called dichoptic. The Cyrtidte have contiguous eyes 

 in both sexes (with rare exceptions), and in some cases the eyes 

 are contiguous both above and below ; the Mydaid.e, Asilid.i;, 

 DoLiCHOPODiD^, LonchopteriDj*;, and CoxopiM:: have the eyes 

 equally conspicuously separated in both sexes. The lower Antho- 

 MYJNiE and practically all the Acalyptrata are also dichoptic. 

 The eyes may be pubescent or bare, this being sometimes a sexual 

 character, and in life they are often green {Ha;matopota) or golden 

 green {Clirysopilns), and in many species of Taba^s^id.e, Asilid^ 

 aud some other groups bear brown or purple bands. In many 

 groups the front facets are from just perceptibly to very con- 

 siderably larger than the rest in the 6 , and of iniifoi-m and 

 smaller size in the 5 , but in the Pipunculid.t: the front facets, 

 though enlarged more than usual in the S , are yet more enlarged, 

 and to an enormous extent, in the 5 . In some Pupipara the eyes 

 are absent; in Cyrtid,i; and Pipuncumd.t; they occupy practically 

 all the head, no other parts except the antennae being visible in 

 profile in some species of both families. 



Three ocelli are ]iormally present in all the Brachycera, but 

 they are occasionally absent (Coxopin.t;). 



The lower part of the head, or epistome, exhibits a wide range 

 of shape and size, from being barely or not at all produced beyond 

 the eyes in profile either forwards or downwards (as in most 

 PiPUNCULiD.15) to forming a long strong conical rostrum {Nemoielus 

 ill Ktratiomyid.t; ; lihingia, Volucella, LycastrU in Syrphii).^). 

 The face frequently has a central bump, as in most SYRPiiiD.ii:, or 

 it may be less prominent, gently curved, or flattened. The mouth- 

 parts attain their highest development in the Tabaxid.e, a family 

 in which the females of all the species have the reputation of 

 being blood-suckers. The parts of the female Tabanid mouth 

 consist of the labium or lower lip, a pair of maxillae and of 

 mandibles, strong piercing organs, and a pair of large, fleshy, 

 conspicuous, approximately conical maxillary palpi.* The pro- 

 boscis in the Bracuycera is usually soft, and formed for sucking 

 the juices of plants or animal matter, but it is not infrequently 

 of enormous length, longer than the whole body and of extreme 



* Compare ' Indian Diptera,' i. p. 18. 



