NEW SPECIES OF AFRICAN SIMULIIDAE. 459 



dichotomousl}' and then dividing once again, forming three in all ; and the third 

 dividing dichotomously and once again in the same way but nearer the base. This 

 is a ver}'- common type. 



Pupa var. dubium, nov. (PI. xiv, fig. 3). — The filaments are eight in number, 

 but the second stem divides again very much more distally from the base, and the third 

 main stem divides again at about two-thirds the entire length from the base. 



The typical pupa and this variety were taken from the same localitj' and on the 

 same date as the male type. 



Pupa var. adersi nov. (PI. xiv, fig. 6). — The respiratory filaments are 11 in 

 number, arising from three main stems at base : the first divides into three branches ; 

 the second divides into three, the first two again dividing dichotomously, making 

 five in all ; and the third divides into three very near the base. The position of the 

 branching of the third main stem varies greatly, even in the filaments on either side 

 of the same individual. The same number and general arrangement seems ver}^ 

 constant in this form, no really intermediate forms having been obtained as yet. 



East Africa : Zanzibar, 22.vii.1917, from grass blades in small stream. 



The genitalia of the males, the female structure and the general coloration of 

 the adults appears to be the same in all specimens bred from or dissected from the 

 three types of pupae. 



Simulium alcocki, sp. nov. 



Q. Length, 1-5 mm. Antennae dark brown, covered with grey pubescence, the 

 first two segments naked and distinctly reddish-brown. Thorax and scutellum, 

 ver}' dark velvet-brown, covered with light golden pubescence. Pleurae fuscous, 

 lacking patch of soft hair. Wings hyaline, radius unforked. Abdomen velvet-black, 

 basal scale bearing a long fringe of pale vellow hairs, a diagonal lustrous blue stripe 

 on either side of the 2nd, 5th and 6th segments. Legs : front legs, coxae and femora 

 straw-coloured, dark brown at apex, tibiae straw-coloured, dark brown just at basal 

 joint, more so at apex, tarsi dark brown ; hind legs, coxae yellow, femora yellow, 

 brown at apex, tibiae yellow, dark brown at base and apex and along outer margin, 

 metatarsi pale yellow, dark brown at apex and along inner margin, remainder of 

 tarsi brown, second tarsal joint with slight excision near base. Genitalia (PI. xiii, fig. 4): 

 basal pieces large ; claspers about two-thirds the length of the basal pieces, rather 

 thick, tapering at apex, which bears a short finger-like process ; anal plates long, 

 rather cup-shaped at apex and bearing numerous hairs and bristles ; adminiculum 

 broad, apical margin forming a lip covered with a fringe of short curved hairs ; arms 

 ending mesally in a single long strong spine, turned back outwardly. 



Habitat. — Bred from pupae attached to grass blades in slow-moving stream. 



Nigeria : Ibadan, 500 ft., 6.xii.20. 



Type in the British Museum. 



$. Length, 1 -6 mm. Head : frons and face grey, covered with silver pubescence ; 

 antennae fuscous, covered with short grey pubescence, the first two and part of the 

 third segments deep orange. Thorax dark lustrous grey, completely covered with 

 dense brassy pubescence in the case of freshly emerged specimens, silvery towards 

 outer margin. Pleurae brown, lacking patch of soft hairs. Wings hyaline, radius 

 unforked. Abdomen dark brown, the first six segments covered with golden hair, 

 the 7th and 8th texgites rather bare, shining, with a few sparse black bristles. Legs : 

 front legs, coxae yellow, femora and tibiae yellow, dark brown at joints, tarsi brown ; 

 hind legs, coxae yellow, femora yellow, black at apical joint, tibiae brown, yellow 

 at base and banded yellow across middle, metatarsi pale yellow, dark brown at apex, 

 remainder of tarsi black, second tarsal joint with excision near base ; claws with 

 prominent tooth at base. 



(5296) 2 L 



