262 Annals Entomological Society of America  [Vol. VII, 
June—build large, flat catching-nets about a square decimeter 
in size. In the centre is an opening, (about 8 to 10 mm.,) which 
leads into a funnel about 5 to 6 cm. long—the hiding place of 
the larva. This is hidden under a stone or leaf. The mesh is 
very coarse on the outer edges of the net. The water being 
very shallow in the brook, the nets lie nearly horizontally on the 
stones. The organisms caught in the nets by the larve are 
principally gnat-larve, Asellide, etc., which are swept along 
by the stream into the net. 
Polycentropus. 
The net of Polycentropus flavomaculatus Pict. was first 
described and figured by Petersen (1907). The nets resemble 
swallows’ nests and are about 30 mm. long, 20 mm. wide at the 
entrance, and about 15 mm. high. They are found singly on 
the bottom of slowly flowing brooks attached by their fore 
corners to small stones. The mouths face the current and are 
held expanded by the water. The larve are always found in 
the bottom of the net. When found on vertical banks, the 
mouths stand perpendicularly. The nets are also found on 
the wave beaten shores of the larger lakes. The nets are 
bluish-green in color. 
Holocentropus. 
The larve of the genera Holocentropus and Cyrnus live in 
quiet water, principally among alge and water plants of the 
smaller lakes and pools. The nets, which are hard to observe, 
have been completely overlooked before Wesenberg-Lund’s 
paper (1911). He first saw the net in June 1909. 
He figures three forms of nets which he found made by 
Holocentropus dubius. One type of net is in the form of a 
shallow funnel attached by silken threads to Sium leaves. In 
the centre is an opening which lands into a thick web-like 
tube which extends to the main stem of the plant. In this 
passage the larve live and may escape through an opening at 
the hinder end. The second type is found where there are thick 
mats of filamentous alge, as Spirogyra. In this loose mass 
may be seen perpendicular tunnels 8 to 10 cm. long, covered 
with spinning; these are open below and also open at the sur- 
face in the middle of a shallow funnel-like net of very fine 
mesh. The larve sit at the bottom of the funnel-like recess 
