Syrphidae. 21 



generally a little upwards at the inner eye-margin below, so that short 

 and narrow eye-margins — rudiments of cheeks — are formed, and 

 in a few genera, especially in Chilosia, the furrow stretches up towards 

 the antennæ, separating off the cheeks as narrower or broader eye- 

 margins on each side. The oral cone is ahvays well developed, it 

 and the proboscis are of various length, from rather short to con- 

 siderably long, but generally of medium length; they are longest in 

 forms with a strongly protruding epistoma and elongated oral aper- 

 ture as Rhingia. The clypeus is shorter or longer; it is deeply in- 

 cised in the anterior part and thus elongated horse-shoe-shaped ; the 

 basal part is shorter or longer, and at its upper ond is a small piece 

 which is somewhat separated or indistinctly jointed, so that it is able 

 to be angularly bent against the other part and aets as a hinge when 

 the proboscis is laid up; this small upper part is situated just towards 

 the front mouth edge in the bottom of the mentioned incurving. The 

 mouth parts are shorter or longer according to the length of the pro- 

 boscis, and they are characteristic for the family. There are always 

 maxillæ present. Labrum somewhat strong and strongly semitubular; 

 its apex is of a characteristic shape; it is always divided into five 

 processes; the median process is cleft, generally to the base, each 

 part of it is pointed and generally bears spines or emergences on the 

 margin and especially at the apex; the upper lateral processes are 

 generally very delicate, pointed, sometimes broader at the base, 

 attenuated towards the apex, and they have sometimes some emer- 

 gences or are a little serrated at the margin; the lower lateral pro- 

 cesses are broad, much broader than the others, and they are broad 

 at the apex, nearly always with the lower or outer corner rounded, 

 the upper or inner more angular or drawn a little out; sometimes 

 the shape is a little altered; the labrum has on each side below a 

 lateral row of small papillæ or warts. Hypopharynx about of the 

 length of labrum, forming a more or less slender, blade-shaped organ 

 with parallel sides; it is attenuated at the apex, but the apex itself 

 is nearly always rounded; the hypopharynx is semitubular with the 

 margins curved upwards; the salivary duet is always distinct. The 

 maxillæ have a characteristic, slightly curved, knife-shaped lacinia which 

 is shorter than hypopharynx, in a few cases rather short; it is always 

 densely beset with very small, microscopical spines which are arranged 

 somewhat in longitudinal rows and are most distinct at the apex; 

 the maxillary palpi are one-jointed; they are shorter or longer, from 

 very short to being of a considerable length; they are thread-like, 

 sometimes a little clubbed, and they are densely beset with micro- 

 scopical hairs and bear some bristles at the apex or in the whole 



