ON THE BRITISH SPECIES OF SIMULIUM — II. 241 



References. — Tlie larva and pupa have been figured (rather inaccurately) by 

 Lt.-Col A. Alcock in Entomology for Medical Officers, 1911, p. 126. There is also a 

 very good and detailed description, with figures, of the tracheal system of both larva 

 and pupa by Taylor (Trans. Ent. Soc. London, 1902, p. 701). Neither of these 

 authors however had named the species. The species in which Weismann (Abh. 

 Senckenberg. Natf. Ges. iv, p. 249, 1862) studied the development of the tracheal 

 system would also appear from his figures to be S. latipes, not S. sericeum. 

 Friederichs (Zeitschr. f. angew. Ent., vi, p. 61, 1919) sinl^s latipes, Mg., as a 

 synonym of maculatum, Mg., but this seems to me to be without justification. 



12. S. angustitarsis, Lundstr.* (figs. 11, in). 



Larva. — Head with eight dark spots above, four arranged in the usual cross- 

 like formation, the other four in two transverse pairs near the posterior margin ; 

 a dark stripe over the eyes, including a small blackish dot. Antennae much as in 

 S. aureimi, the second and third joints a little longer. Mentum as in S. aureum. 

 The other characters cannot be given, as the only two larvae which have yet been 

 found had partly transformed to pupae. The head-markings should be unmistake- 

 able, though similar to those of S. aureum. 



Pupa. — Respiratory filaments four in number, longer than the pupa, all arising 

 practically from the same point, widely divergent at the base, the upper two con- 

 siderably swollen basally. Cocoon as in S. latipes, except that the anterior 

 projection is usually very short. 



Habitat. — Weedy rivers with only a moderate current, in company with other 

 species, such as S. ornatum, S. argyreatum and S. equinum, but always in much 

 smaller numbers, and might usually be regarded as rather scarce. Very rarely in 

 small stream^s. 



Breeding Season. — Nothing definite can be stated except that pupae have been 

 collected from April to July and in September, while females have been taken on the 

 wing in November. 



Material collected. — Pupae have been obtained as foUows : — Camhs. : Stapleford, 

 28.iv.16, on grass ; l.vii.15, on Sparganium. Herts. ; River Lea near Hatfield, 

 V.1916 ; River Ivel near Radwell, 16.vi.l7, on Ranunculus. Suffolk : River Lark, 

 near Mildenhall, 30.ix.l5, and 25.iv.16, on Sparganium. Hants. : River Test 

 {M. E. Mosely). Wales: Anglesey, 19.ix.l5, one pupa on stone in small stream 

 across field (C. B. Williams). 



Additional locahties for the adults are : — Timworth, Suffolk {Lt.-Col. Nurse) ; 

 Wicken, Cambs. (F. W. E.); Shefford, Beds. {F. W. E.); Oxford district {A. H. 

 Hamm) ; Woolhampton, Berks. {A. H. Hamm). Besides these, females were 

 wrongly recorded as S. latipes in my previous paper from Bovisand, Devon ; Corfe 

 Castle, Dorset ; and Stockenchurch, Oxon. 



Variation. — ^Very little noticed, but the femora and tibiae of the female vary in 

 ground-colour ; the Hghtest specimens show most distinctly the dark ring near the 

 base of the hind tibiae, while in the darkest it is barely distinguishable. The hind 

 metatarsi are always dark. 



* See synonymy below, and under 8. aureum. 



