AQUATIC INSECTS 



899 



(Fig. 1370) feed upon fresh- water sponges, and live within the oste- 

 oles of the same, or in depressions on the exterior of the sponge mass. 

 They puncture the tissue of the sponge with their long decurved 

 sucking mouth parts. The paired appendages of the abdominal 

 segments are bent downward underneath the body, and curiously 

 angulated; they are moved back and forward with a rapid, inter- 

 mittent, shuttle-like vibration. In 

 the well-grown larvae, the stomach 

 has no posterior opening, and the 

 sponge substance taken up through 

 the slender proboscis appears to be 

 wholly absorbed. Correspondingly, 

 the posterior part of the alimentary 

 canal and its appendages are put to 

 a new use. The malpighian tubules, 

 or nephridia, are metamorphosed in 

 large part into silk secreting organs, 

 the rectum into a silk reservoir, and 

 the terminal aperture into a spin- 

 neret. When grown the larva leaves 

 the water and climbs to some suitable 

 supporting surface, and spins with this 

 apparatus first a wide canopy over 

 itself, and then a closer fitting inside 

 cocoon. Climacia weaves the outer 

 covering in a beautiful hexagonal 

 mesh; Sisyra makes both coverings 

 plain and close woven. Nothing is known of the feeding or egg- 

 laying habits of the adult, or of any other particulars except that 

 they are sparingly attracted to lights. 



It should be mentioned, perhaps, in passing, that the immature 

 stages of another genus of Hemerobiidae, Polystoechotes, the genus 

 containing our largest representatives of the family, are as yet 

 unknown. 



FIG. 1370. The larva of Sisyra. 



