Genus Nyssorhynchus. 
61 
Thorax is black with a frosty appearance. The scales are the 
same as in the female. 
Abdomen is black, the last segment alone has a few flat 
Fig. 23. 
Nysso¬ 
rhynchus 
tibani. 
Palmate 
hair (after 
Patton.) 
Fig. 24. 
Head of larval Nyssorhynchus tibani. 
Patton (after Patton). 
scales on its sides. Genitalia, medium-sized basal segment, apical 
segment is dark tapering to a fine point. 
Wing same as in female, legs also the same, ungues unequal 
and uniserrated. 
Habitat .—All rivers and springs in the Aden Hinterland, as 
far up as Jehaf (6,800 feet). 5 ’ 
Life-history .—Patton records the larva and ovum as follows :— 
“ Larva, head dark brown to black, thorax and abdomen also 
dark brown. Cephalic ornamen¬ 
tation as shown in figure. The 
antennae have a small spine situ¬ 
ated on the outer border ; frontal 
hairs are simple and unbranched. 
Palmate hairs are present from 
second to seventh segment inclu¬ 
sive. Blade (fig. 23) is long with 
marked serrations on one of the 
shoulders, the other has generally one notch. The filament is 
long and pointed. 
“ The egg is boat-shaped with long narrow floats which extend 
almost to both ends. They extend up to the frill, which is 
narrow and not marked. The floats do not approach each other 
in the middle line. It only breeds in running water and pools 
Fig. 25. 
Ovum of N. tibani. Patton 
(after Patton). • 
