HYDRELLIA. 255 



unguiculate. Every facet of the eyes appears to produce a short erect 

 hair from its centre, which gives a velvety pile to the whole, and an 

 indefinite outline when viewed by a magnifier, unless in the direction 

 of a row of the lenses. 



SYNOPSIS OF THE SUBGENERA. 



r convex 1. HYDRELLIA. 



f pectinated above. Face < 

 A . , ) (.impressed 2. ATISSA. 



(.very minutely pubescent 3. GLENANTHE. 



Subgenus 1. HYDRELLIA. 



HYDRELLIA, Desv.; Hal. A. N. H. iii. 401 (1839). 



Fades convexa, superne attenuata, squamuloso-micans, puncto lucido an- 

 tennarum basin superante. Palpi subdilatati. Antenna; articulo tertio 

 ovato aut orbiculato, compresso, deftexo ; arista dor so peciinata. Ala 

 apice rotundatce. Vena discali-recurrens ab alee margine parum dis- 

 tans. 



Face convex, attenuated above, shining, as if squamulose, with a lucid 

 spot above the base of tJie antennae. Palpi slightly dilated. Antenna 

 with the third joint oval or orbiculate, compressed, dejlexed ; arista pec- 

 tinated above. TFings rounded at the tips. Discalrrecurrent vein near 

 the border of the wing. 



The species of this group generally occur in great profusion in 

 their favourite localities, and are subject to some variation in the 

 colour of the face, antennae, and mouth. The general colour of 

 the body is rather uniform, ranging from a dull olive or cinereous 

 shade to a shining black. The halteres are sulphureous, with the 

 base black in the dark-coloured species, brown or tawny in the 

 others. 



1 . Cardamines, Hal. A. N. H. iii. 402. 1 (1839). Nigro-anescens, 

 antennis subtus facie ore palpis coxis et tibiis anticis totis tibiis posterio- 

 ribus apice tarsisque basi fulvis. Var. j8. Facie albo-micante. Var. y. 

 Antennis et mento nigris. Long, f-li lin. 



JEmeous-black. Antennae beneath, face, mouth, palpi, coxes, fore tibia, 

 hinder tibia at the tips, and tarsi at the base taiony. Var. /8. Face with 

 white reflections. Var. y. Antenna and mentum black. 



Among aquatic plants, at Hollywood, near Belfast ; local, but 

 not rare. (I.) 



2. flaviceps, Meig. Zw. vi. 72 (1830) ; Mcq. ; Hal. aurifacies, 

 Desv. Obscure viridis, ore palpisquejlavis,faciejlava albo-micante, an- 

 tennarum articulo tertio tibiis tarsisque fulvis, tibiis posticis annulofusco. 

 Long. 1 ; alar. 2 lin. 



