RHYNCHODEXIA. 995 
RHYNCHODEXIA. 
Rhynchiodexia, Bigot, Bull. Soc. Ent. Fr. 1885, p. xi. 
Rhamphinina, Bigot, loc. cit. 
Head hemispherical; front somewhat prominent, very much narrowed i in the male ; face perpendicular, usually 
distinctly, but not sharply, carinated in the middle; vibrissal swellings parallel or nearly parallel, only in 
some species slightly convergent ; vibrisss inserted at some distance above the oral margin, which is 
rounded, slightly prominent, and laterally beset with a row of bristles; cheeks broad, their lower 
portion more than half as long as the longitudinal diameter of the eyes; occiput somewhat swollen on 
the lower part. Eyes bare. Antenne short, inserted below a line drawn through the centre of the eyes ; 
arista distinctly pilose. Proboscis exserted, as long as, or a little longer than, the head; palpi cylindrical, 
scarcely thicker towards the tip. Abdomen conical or elongate-oval, with discal and marginal macro- 
chete. Legs long and slender, with scattered bristles ; foot-claws and pulvilli elongate in the male. 
Wings longer than the abdomen; apical cell opened at some distance before the wing’s tip; curvature of 
the fourth vein more or less angular, without appendage; posterior cross-vein inserted beyond the middle 
between the small cross-vein and the curvature of the fourth vein. 
From Hystrichodexia and Bathydexia this genus may be distinguished by the more 
elongate shape of the body and by the less numerous and more regularly arranged 
macrochete on the abdomen; from Bathydexia, moreover, by the vibrissee inserted at 
some distance above the oral margin, and by the absence of an appendage at the 
curvature of the fourth vein. In this latter negative character and by the proportion- 
ately shorter antenne, Rhynchodexia differs from Scotiptera. 
The genus Rhynchiodexia (Rhynchodexia i is grammatically more correct) was founded 
by Bigot for a species from New Caledonia, and characterized in a very incomplete 
manner as having the proboscis exserted, thin, aud rigid, but shorter than in. Prosena. 
At the same time he established two other Dexid genera with elongate proboscis: 
Rhamphinina and Siphoniomyia, each with one Mexican species (Rhamphinina dubia 
and Stphoniomyia melas). Of the last-mentioned I have examined the typical specimen, 
and it proves to be not a Dexid at all, but a Tachinid of the genus Trichophora in the 
sense adopted by me, anted, Pp. 30. The genus Siphoniomyia, Big., may thus be passed 
over in silence. © 
In the ‘Revue d’Entomologie.’ 1885, pp. 259 et seq., Bigot has given a synoptical 
table of the genera of Dexine. According to this table, Rhynchodexia and Rhamphi- 
nina should be distinguished from each other by the facial carina being present in the 
former and absent in the latter. This character, however, is insufficient to separate 
the two genera, because the species belonging to them show numerous transitions with 
regard to it, and even Bigot himself has not been consistent in its application: For 
instance, his Rhamphinina formidabilis (which I include in the genus Hystrichodexia) 
and Lhamphinina anthracina have a very distinct facial carina, whilst, on the contrary, 
it is inconspicuous in his Rhynchodexia tincticornis, as I have seen in the typical 
examples of these species kindly sent me by M. Bigot for examination. ‘These facts 
justify me in uniting the two genera. ; 
In the genus Ahynchodexia I include an extensive series of Central-American species. 
BIOL. CENTR.-AMER., Dipt., Vol. II., May 1891. 29 
