IXTEODUCTIOX. 



11 



slenderness, and in this state either adapted for pierciug 

 the skill (Pangonia) or for imbibing the juices of i^owers 

 (NemestmjStid.t: , Cyrtid.t:, and many Bombylib^e). Occasionally 

 it is long, rigid, and geniculate (Co^'OPID,E). Biting flies are 

 disti-ibuted throughout many bracliycerous and cyclorrbaphous 

 groups. Si/rjijjhoromyia, in Leptid.e, has been definitely proved 

 to bite man severely on occasions ; the Tabanid.e generally confine 

 their unwelcome attentions to the larger mammals, though one 

 genus, Hccmatopota, widely distributed throughout the world, its 

 luitural home being apparently Africa, is very prone to attack 

 man. The strong horizontal horny proboscis of the Stomoxys 

 group of true Muscinids is well known, as are also the tsetse-flies 

 (Glossina) inhabiting Africa, these being the carriers of sleeping- 

 sickness. PJiiheinatomt/ia, a genus of Muscinid flies, possesses a 

 circlet of teeth-like prt)jections at the tip of the proboscis with 

 which, even if unable actually to pierce the skin, it can easily 

 enlarge an abrasion already made. The proboscis in not a few 

 genera is rudimenlary, in some almost obsolete, as in ffisiKiu.E, 

 the members of which family cause cattle instinctively the greatest 

 terror on their approach for the purpose of depositing their eggs 

 on the animals' mouths, nostrils, etc. An isolated case occurs 

 here and there of a genus with a strong rigid proboscis in a group 

 in which the organ is normall}" soft and fleshy, as Dripneia in the 

 AjS'tuomtix^e. The Asilid.e and Empii),e are two other extensive 

 families generally possessing a rigid horny proboscis, with \vhich 

 they easily pierce and carry off their prey, consisting of softer 

 Diptera and other insects. The lahella, sometimes called " sucker- 

 flaps," vary in size, shape, and strength, sometimes being small 

 and soft, in other cases acting as organs of attrition to rub off 

 small particles of food. 



The palpi, apart from those of the jVematoceua, consist usually 

 of two joints, in some highly specialized families of one only, these 

 being the maxillary pair, the labial palpi being considered to be 

 absent in the Diptera. Though large and prominent in some families 

 (Tabaxid.e), it is often difficult in others (BoMBYLiiniE, Theue- 

 viD.E, Asilid.e) to examine them without removing the dense 

 furry or bristly pubescence characterising these groups. Howe\ er, 

 in most of the Braciiyceija the location of any genus or species 

 can be readily ascertained without reference to these organs. 

 They are normally porrect, i. e., directed horizontally forwards, 

 especially in the blood-sucking Muscids, but frequently project 

 more or less downwards, and they may be present or absent, 

 respectively, in genera of considerable affinity, whilst in the 

 Cybtid.e they are generally obsolete. 



As regards the antennte, a gradual change takes place from the 

 many-jointed elongate flagellum of the Nematocera to the compact 

 three-jointed form of the bulk of the remainder of the Diptera, 

 the 3rd joint often being the only conspicuous one.* In the 



* For comparative notes on tlie antenna; in Nematoceea and BRAcnTCEitA, 

 see ' Indian Diptera,' i. p. 20. 



