BRITISH FLIES 



19 



the end of the discal cell. Tibiae without spurs or with only 

 very short blunt ones. Thoracal squamae enormous, depressed, 

 and completely covering the halteres. Perfect insects never 

 blood-suckers and never large. VI. Cyrtid^. 



The Cjirtifhv are medium sized to rather small humpbacked flies, 

 with a glolndar abdomen and comparatively (or very) small wings. 

 Their colours are dark with usually yellow or bone-white markings. 

 The head is usually ridiculously small in comparison with the thorax, 

 and is almost entirely composed of the two eyes. The mouth opening 

 is sometimes closed hy a membrane, but in some (not British) species 

 there is a very long, thin, horny ]irol)oscis bent back under the body. 

 The larvie are parasitic on spiders, l)ut (as far as known) the perfect 

 insects are harmless. They may be distinguished from all other 

 Beaohycera by the enormous thoracal squamae and the globular 

 abdomen. 



11 (2) Wing-veins running parallel with the hindmargin of the wing 

 (fig. 41) in a very different fashion from any other Ehemo- 

 CH^TA, and often reticulate. 



The venation has some other peculiarities, as there is a 

 " diagonal vein " which runs as a continuation of the cubital 

 vein almost straight from its l)ase to (or almost to) the hind- 

 margin of the wing, and when the discal cross-vein is present, 

 it is placed very near the tip of the discal cell. Antennae 

 with the third joint simple and bearing a terminal style. 

 Aerial insects of rather large size. V. NEMESTRiNiD^^i. 



Fus. i\.—Nniir^tfinn Pf're.-.ii ?. x S}. 



The Neviestriniihe inhabit the hot dry regions of the world, and 

 only a few occur in the South of Europe of which none are ever likely 

 to occur in Britain. Some of the species have most peculiarly reticulate 

 wings, and some have the proboscis longer than in any other Diptera. 

 The larvai are parasitic. 



