DIPTEKA. 3 



wings differ from DIPTEEA. Still more remote is the relation to 

 the male Stylopidce, in which it is the metathorax, with the 

 hinder wings alone, that are developed, and the position of the 

 seeming halteres (fore wings) is relatively the inverse. Among 

 HYMENOPTERA, the genus Mymar has the hinder wings only 

 rudimental, but they take the form of a bristle merely. 



The wingless species of Diptera may be distinguished from 

 those of most other orders, (HEMIPTEEA and NEUROPTEEA p., sc. 

 Forficulidce, Podurella, Mallophaga, Termitida, Psocidte, Phy- 

 sapoda, spp. &c.,) by the 5-jointed tarsi ; and where this mark 

 fails (from COLEOPTEEA, HYMENOPTEEA, and the other wingless 

 NEUEOPTEEA), by the want of nipping jaws, or of the maxillary 

 spiral sucker (of LEPIDOPTEEA) ; without going into the other 

 distinctive characters. 



In Diptera, the labiurn seems to be the true pump, or instru- 

 ment of suction. Accordingly, where the fly merely imbibes 

 excreted juices of plants, &c., we find the labium much longer 

 than the rest of the oral organs (e. g. Conops, Siphona, Musca, 

 Hydrotaa, Tephritis, and most of the Mutcida, the Syrphidce, 

 PipunculiddBj &c.). But where the fly preys on other insects, 

 there is a borer (composed of labrum, tongue, and usually also 

 maxillae) nearly as long as the labium (Asilicfa, Empida, Scato- 

 phaga, Ccenosia, Cordylura, &c.) ; and where they have to pierce 

 the skin of larger animals, to make the blood flow to the sucker, 

 this development is more evident (Stomoxys), sometimes the borer 

 being reinforced with mandibular lancets (Tabanida, Culex, 

 Phlebotomus, Ceratopogon, Simulium*). The comparative short- 

 ness of the labrum and tongue in some of the family Dolichopida, 

 which are all predaceous, is only apparently an exception; see 

 further under that head. The length of the labium is not an 

 obstacle to the borer going deep; for while its extremity con- 

 tinues to embrace and steady the lancets of the borer, the inter- 

 mediate length may be detached from them, in a loop, allowing 

 the liplets to slide back as the borer penetrates (e. g. Culex], 



* The entire mouth forming a cupping apparatus. 



B 2 



