POLYCENTROPIDA. PHILOPOTAMIDE. 
FAMILY PHILOPOTAMIDE. 
The larve are common in most swift streams of the region. 
Among the stones of the bottom, where the force of the cur- 
rent is broken, they spin delicate nets of fine silk. In form the 
nets resemble the finger of a glove, attached at the open end, which 
is directed upstream, and free at the closed end. In the closed 
end of the net there is a small slit, just large enough to allow the 
escape of the larva in case of danger. The nets are 25—4o mm. 
in length and 3—4 mm. in breadth. They often occur in great 
numbers, completely covering the stones with a thin flocculent 
mass of dirty silk. 
Though these nets cannot stand the full flow of the unbroken 
current, it is necessary that they be situated where there is enough 
flow of water to keep them distended. On lifting a net-covered 
stone from the water the nets invariably collapse, appearing as 
a mass of diatomaceous ooze through which the larve rapidly 
wriggle backward. 
While the nets of the Philopotamid larve serve as hiding- 
places, their principal function is to serve as sieves through which 
the flowing water is strained ; the larve feeding on the microscopic 
organic particles that are entangled in the mesh. 
Description oF Larva:.—In color the larve are orange or 
yellow. The head is compressed; the labrum is entirely mem- 
branous; the cephalic margin of the frons is asymmetrical; the 
mandibles are asymmetrical, without tufts or bristles. The pro- 
thorax is the only thoracic segment that is chitinized dorsally. 
The abdomen has but few long hairs; the prolegs have but two 
long and two short bristles, slightly above the drag-hooks; gills, 
spacing-humps and lateral fringe are lacking. 
DEscRIPTION OF THE CasE.—Until nearly time for pupation 
the larve build the silken nets previously described. Before pupa- 
tion they cover themselves with a rather irregular dome of pebbles, 
between which respiratory aperatures are left. 
A careful study of the habits of the larvae was made by Miss 
Alice Noyes, 1914, followed by a more detailed study with de- 
scriptions of the immature stages, the results of which are as 
yet in manuscript. On the results of this work the present account 
of the family and key to the species are based. 
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