Chilosia. 123 



including the central knob is more or less protruding, sometimes rather 

 strongly, and likewise more or less descending, generally only slightly; 

 in a single case (maculata) the central knob and the front mouth 

 edge are fused together. On account of the protruding epistoma the 

 oral aperture is rather large and elongated; the oral margin has a 

 special shape as the side margins end in front with a somewhat 

 drooping point or lateral angle, and the front edge between the points 

 or angles is more or less incurved, the curvature stretching forwards 

 and more or less upwards; (something similar is found in species of 

 Chrysogaster f. inst. Macqiiarti, and for the rest also in other Syrphids, 

 but to a slighter degree). In the female the epistoma is as a rule 

 more hollowed with the central knob and the lower part more pro- 

 minent than in the male. The epistoma is black, only in a few species 

 it has a yellowish or reddish spot below the eye; it is bare and shining 

 or sometimes more or less pruinose, but in one group of species it has 

 erect hairs on the sides. At each side of epistoma the cheeks are 

 separated off as more or less narrow so-called eye-margins by a deep 

 furrow, stretching upwards to somewhat below the antennæ, and 

 downwards to below the eye, here ending with a more or less distinct 

 pit; the epistoma and the cheeks are thus well separated. The cheeks 

 — eye-margins — bear shorter or longer hairs. The jowls are broad 

 but slightly or not descending. The oral cone well developed with 

 the elongated horse-shoe-shaped clypeus lying on the front side. Pro- 

 boscis shorter or longer; labrum (chloris) long, strongly semitubular; 

 the apical processes of equal length, the median and upper lateral 

 delicate, pointed, the former cleft in the whole length; the lower 

 lateral process broad and blunt at the end; along the lateral margins 

 of labrum is on the inside a row of small papillæ or warts; hypo- 

 pharynx a little shorter than labrum, somewhat attenuated but the 

 apex rounded; it is also semitubular; maxillæ with a slightly curved, 

 knife-shaped lacinia, and a somewhat long, thread-shaped palpus, a 

 little longer than the lacinia and a little dilated at the end and here 

 with some fine bristles. The palpus is densely clothed with short 

 hairs and the lacinia very densely beset with small spines, placed in 

 longitudinal rows, but they require a high magnifying power (!2— 300) 

 to be distinctly seen. Labium with a somewhat long basal connecting 

 membrane, and with the well chitinised basal part a little longer than 

 the elongated oval labella. Thorax about quadratic or a little rect- 

 angular ; it is densely haired above with longer or shorter, erect hairs 

 in the male, but as a rule with short, more or less depressed hairs in 

 the female, rarely in this sex haired about as in the male. Scutellum 

 black, in a small group of species orange at the tip in the female; it 



