1920.] • 271 



accumulated since 1901. This particularly applies to his Group V, in 

 which he described only three species — f/enicitlatiisMg., littoralis Beck., 

 and sylvaticus Mg., Avhile the present paper deals with seven. The 

 whole genus is a difficult one, owing to the remarkable uniformity in 

 structure throughout ; while, in the case of the species of the above 

 group, their small size adds to the difficulty of distinguishing the 

 characters upon which the species are based, making the use of a micro- 

 scope almost a necessity. 



The group is distinguished by the venation — ^the discal cross- vein 

 being at or about the middle of the discal cell, and the third costal 

 segment very short, without a darkened stigma. 



The British species may be tabulated as follows : — 



Hales. 



1 (4) Eyes touching- on the frous for a very short space. At least the front 



part of thorax conspicuously greyish when viewed from in front. 



2 (3) All the thorax greyish. Abdominal hairs pale ....1. littoralis Jiccli. 



3 (2) Only the front part of thorax greyish. Hairs on the humeri and front 



of thorax longer. Abdominal hairs dark 2. niinimus Beck. 



4 (1) Eyes touching for a longer space on frons. Thorax not greyish when 



viewed from in front. 

 •5 (6) Hind tarsi with a postero-dorsal ciliation of longish black hairs on at 

 least the first two joints 3. cilitajsis Strobl. 



6 (o) Hind tarsi not ciliated. 



7 (8) Hypopygium without a broad membranous depression, but with a 



somewhat diagonal groove or fold on the right. Only the last joint 

 of (at least anterior) tarsi darkened. Hind trochanters armed with 

 3-4 distinct short bristles at base beneath 4. sylvaticus Mg. 



8 (7) Hypopygium with a broad mendjranous depression. Tarsi often 



darkened. Hind trochauters unarmed. 



9 (10) Hind femora with an outstanding postero-ventral cilia of delicate pale 



hairs 5. geyiiculatus Mg. 



10 (9) Hind femora with normal pubescence. 



11 (12) Humeri j^ellow. Tarsi darkened. Hind trochanters with a slight 



rounded projection composed of dense soft pubescence. Abdominal 

 sternites clothed with brown velvet-like pile ... .6. niyritulus Zett. 



12 (11) Humeri dark. Tcirsi with only last joint darker. Hind coxae and 



abdominal sternites bare 7. Jlavitavsis, sp. n. 



Females. 



1 (2) Abdominal hairs pale , 1. littoralis Beck. 



2 (1) Abdominal hairs dark. 



3 (0) Frons all dull, dusted greyish, even if only sparingly so on upper part. 



4 (5) Frons all conspicuously dusted greyish. Aculeus perfectly straight, 



Unsues rather shorter 2. minimus Beck. 



