The Simulide of British Guiana. 251 
The thorax is short and broad, the dominant colour being brownish blue 
with a bluish reddish iridescence ; there are many pretty golden yellow hairs 
specially on the outer margin. On this background is a prominent character- 
istic pattern of a deep black beautiful velvet appearance (see fig. 2). The 
metanotum and scutellum are of a bluish metallic colour. 
The abdomen is dark, fuliginous, of a metallic appearance and without any 
definite markings. A few hairs are scattered on the 7-8 segments. 
The wings are short and broad ; they show beautiful metallic interference 
colours more particularly green and _ rose. 
The venation of the wings is that characteristic of Simulide and is shown 
in figure 3. 
The first three veins are brown and prominent. The costal vein is stout 
and extends to the end of the wing. V. ii joins the costal one-third of the 
distance from the base. V. iii. 1. is well marked and joins two-thirds down the 
costal while V. iii 2 and 5 are united to one vein joining the costal at the apex 
of the wing. There is a stout cross vein between V. iii 1. and V. iii 2 and 5. 
Veins V. 1 and 2, V. 3, VII. 1, VIT. 2, VIII. are represented but faintly. Vein 
IX. is stout at the beginning but becomes faint later when undergoing the 
characteristic S-shaped curve. 
The above venation nomenclature is based on the following analogies :— 
Costa—Vein I. Cubitus—Vein VII. 
Subcosta—Vein II. Ist Anal Vein—Vein VIII. 
Radius—Vein ITT. 2nd Anal Vein—Vein IX. 
Media—Vein V. 3rd Anal Vein—Vein XI. 
The Halteres are yellowish white. 
The legs have important distinctive characters. In the first pair the coxa, 
femur and tibia are light coloured, while the whole of the-metatarsus and 
tarsus is brown. 
In the second pair of legs the coxa, femur and tibia are light brown, but the 
metatarsus is white and the four segments of the tarsus brown. 
In the third pair of legs the coxa and femur are brown ; the proximal half 
of the tibia is white and the distal brown, the metatarsus !s white with a distal 
brown band; the four tarsal segments are brown. 
Imago, male. This insect very closely resembles the female imago. The 
following two important differences suffice to readily separate the sexes. In 
the head the large compound eyes are contiguous. The pattern on the thorax 
so characteristic in the female is equally characteristic in the male. 
Figure 1 illustrates exactly the arrangement of the bands. In all other 
external respects the two sexes are very much alike, 
