SYSTROPUS. 289 



Subfamily SYSTROPIN.E. 



Head distinctly transverse, occiput excavated, bare ; three 

 ocelli on small but distinct tubercle ; neck short ; eyes in both 

 sexes contiguous, bare (with rare exceptions), no indentation at 

 middle of hind margin, front facets in $ rather larger than in $ . 

 Frontal triangle small, bare ; face narrow, one-sixth width of the 

 head at its upper and lower part, and narrowing to one-eighth of 

 the head in its middle, bare. Mouth-opening long and narrow,, 

 extending nearly to the antennae ; proboscis long, slender, porrect, 

 from as long as, to twice the length of the head ; palpi small. 

 Antennae very elongate, thin, porrect, as long as head and thorax 

 together, closely approximate at base and barely diverging till the 

 end of the very long 1st joint, which forms half the full length 

 of the antennae ; 2nd joint one-third of 1st ; 3rd wider, cigar- 

 shaped, with no style or arista. Thorax much arched, especially 

 in front, nearly bare, no bristles, a large prealar depression on each 

 side ; sides of thorax bare or with slight tomentum ; scutellum 

 rather small, slopirtg ; metanotum concealed, except a peculiar 

 pale-coloured membranous tubercle on each side. Abdomen very 

 long and thin, cylindrical, 9-segmented in <S , 8 in $ , bare. 

 Genitalia in cf rather knob-like, in $ sharply compressed. Legs 

 comparatively short and thin ; hind pair much longer and rather 

 thicker ; legs generally bare, except for three rows of spiculesand 

 a few short spurs on hind tibiae, and some " plantar"* spines on 

 the tarsi. In some species there is a spine below the middle- 

 of the hind femora. Wings with anterior cross-vein beyond 

 middle of discal cell ; two, nirely three, submargiual cells ; three 

 posterior cells, always open ; 3rd longitudinal vein widely forked ; 

 anal cell closed; alulae absent, base of wing cuneiform; teguke 

 absent or minute ; halteres long and conspicuous. 



The affinities of this subfamily are not definite, there being no 

 close relationship to any of the others. Only two genera and 

 about forty species are known. The extremely long attenuated 

 abdomen and long thin hind legs, three posterior cells, elongate 

 antennae, and bare body characterise them. 



Genus SYSTROPUS, Wied. 



Systropus, Wiedemann, Nova Dipt. Gen. p. 18 (1820); Loew, 



Fauna Sudafr. p. 200 (1860). 



Cephenes and Systrophus, Latreille, Fam. Natur. p. 496 (1825). 

 Cephenus and Sijstrophopus, Karsch, Zeits. f. d. ges. Naturw. liii, 



p. 656 (1880). 

 Xystropus, Verrall, apud Scudd. Nomencl. Zool. p. 355 (1882). 



GENOTYPE, Systropus macilentus, Wied. (S. Africa) ; by original 

 designation. 



Body extremely attenuated, with long narrow wings and com- 

 paratively short anterior legs, hind legs very long; practically 



* I quote Verrall here. 



