The Simulide of British Guiana. 253 
The face and cheek, are silvery grey with sparse white hairs. The frons and 
vertex are dark with a silvery grey shimmer due to scattered short white scales. 
The occiput and post vertical regions show short white hairs. A thin median 
indistinct black stripe traverses the frons and vertex. 
The thorax is almost square and of a blackish colour with a silvery grey 
shimmer. It is decorated with sparsely scattered short white scales with a 
thin indistinct median dark stripe. The pleurae are bare and brownish yellow. 
The scutellum has black hairs projecting from the posterior edge and short 
white scales on the upper surface. The metanotum is bare with a fringe of 
white scales at the posterior edge. 
The abdomen consisting of 7-8 segments, is reddish brown decorated on the 
three last segments by a few white hairs. 
The halteres are light yellow. 
The wings shew the venation typical of Simulide. The venation of 
S. guianense is identical with that of 8. amazonicum described above. There 
are numerous short hairs and bristles on the costa. 
The leg markings are very characteristic and are as follows :-— 
In the first pair the coxa and femur are light yellow. The tibia is dark 
yellow with a distal band of dark brown colour. The metatarsus is black, 
much swollen and covered with short, stout hairs. The tarsus is much enlarged 
in the seoond and third segments, the fourth and fifth segments are small and 
delicate. The second and third segments are covered with short, stout hairs, 
while the two distal segments carry thin and long hairs. 
In the second pair of legs the coxa is light yellow, the femur yellowish brown, 
the tibia dark brown has a pair of spines at the distal end and is slender (not 
swollen like that of the third pair); the metatarsus is pure white with a distal 
black band and a long row of short, tough spines. The tarsus is dark brown 
with numerous stiff hairs. 
In the third pair of legs the coxa is yellow, the femur brown with a proximal. 
yellow band. The tibia is proximally yellow shading distally to deep brown. 
It is much swollen and is almost club shaped. The metatarsus is white with a 
black distal band, the tarsus is blackish brown with many fine and long hairs. 
The male imago was not found. 
This species of Simulium has some resemblance to Simulium tarsale (12) 
found in the West Indian Island of St. Vincent. In both species the fly is 
blackish with a silvery grey shimmer and in both various members of the 
metatarsus and tarsus:are swollen. 
