39 
which may have already existed. Many of them will immediate!) 
commence to haul themselves back again by walking along the silken 
thread or threads, and this they accomplish by forming the body inn 
a succession of loops, in the same way as they progress along stones 
and plants— the mouth or sucker feet grip the thread finnh 
while the posterior sucker is brought forward until it almost touches 
the anterior segments -the action being repeated until a place of 
safety is reached. Many, however, float down stream supporting 
themselves by their threads until some fixed object is reached. If .1 
leaf or stem supporting a colony of larvae be pulled partly out of tin 
water the larvae will all crawl back again to the stream and usual l\ fix 
themselves to the submerged portions of the same leaf or stem 
Fig 10.—Larva ok Simulium ornatum :— a. maxilla and palpus ; b. mandible . 
c. labrum ; d. labial plate, x l2 5- 
If placed in still water the larvae soon become sluggish and death 
takes place in about 17 hours, but if completely removed from the 
stream and kept in a thoroughly moist vessel they will survive for a, 
much longer period. 
When about to pupate the larva spins for itself a little elongated 
cocoon, shaped somewhat like the toe of a slipper, with a large 
opening at the broad end, and this is almost invariably placed with 
the opening pointing down stream. From this the head of the pupa, 
with its external respiratory filaments, projects and a sufficient suppb 
of oxygen is thus obtained. 
