306 [November. 



In Verrall's *' List of British Diptera," five species of SiniuUvm 

 are noted ; a sixtli (S. hirtijmy) was recorded as British by Austen in 

 1906, The writer has increased this number to thirteen. The species 

 may be separated into two distinct groups. 



Group A. 



Tibiae of front and middle legs with a large patch of silvery-grey 

 dusting on the front or outer side ; legs and abdomen with very fine 

 hair-like pubescence ; thorax and abdomen of the male usually with 

 silvery markings ; last three abdominal segments of female shining ; 

 front tarsi more or less thickened. 



This group contains seven species, three of which {S. variegatum, 

 S. tuberosum, and 8. reptans) are confined to mountainous districts ; 

 two more (8. morsitans and 8. ausfeni) occur mainly in the southern 

 and midland counties of England, while the other two (8. ornatum 

 and 8. argyreatum) are common and widely distributed. 8. reftans 

 and 8. tuberosum are habitual bloodsuckers, and are serious pests in 

 parts of Scotland and the Lake District ; 8. morsitans and 8. argyrea- 

 tum also bite, but apparently 8. ornatum and 8. variegatum do not. 



The species may be separated by means of the following keys. 



Males : 



1. Hind tibiae and metatarsi pale on the basal half 2. 



Hind tibiae pale only at extreme base, if at all 3. 



2. Front metatarsi about 5 times as long as broad 1. ornatum Mg. 



Front metatarsi aboiit 6^ times as long as broad ...2. variegatum Mg. 



3. Hind metatarsi mainly dark and more or less thickened 4. 



Hind metatarsi mainly pale and not at all thickened 



...7. argyreatum Mg. 



4. Middle tibiae conspicuously yellowish or silvery on 



the basal third or half 3. reptans L. 



Middle tibiae entirely, or almost entirely, black (for 

 distinctions between these three species, see 

 figures of genitalia) 4. morsitans Edw. 



5. austeni Edw. 



6. tuberosum Lundstr. 

 Females : 



1. Frons greyish, dull ; claws toothed 2. 



Frons blackish, shining ; claws simple 3. 



2. Fore and mid femora darkened on apical half 1. ornatum ^g. 



Fore and mid femora almost entirely yellow 2. variegatum Mg. 



3. Face dull greyish ; paler species 4. 



