NEUROPTERA. 415 
many processes: the injection of quicklime or of creosote, the 
application of arsenical soap, &c. But it does not appear that 
these processes are infallibly efficacious, nor, above all, easy to 
employ. 
Among other Neuroptera which undergo incomplete meta- 
morphoses we will mention, first, the genera Perla and Nemoura* 

4 
! 
Fig. 383.—Larva of Perla Fig. 384.—Larva of a Fig, 585.—-Perla marginata 
bicaudata. Nemoura. (larva). 
(Figs. 388, 384, and 385), which flutter about the banks of rivers, 
and settle on stones, shrubs, and aquatic plants. Their larvee are 
naked, without cases, and always live in the water, hiding them- 
selves under stones, to watch for small insects, for they are carni- 
vorous. One sees them often balancing their bodies, holding on 
to a pebble. They go through the winter, and only become pup 
in the spring. After moulting, they have the rudiments of wings. 
Very soon afterwards the pupe leave the water, and undergo their 
metamorphosis. The adult lives only a few days, for its mouth is 
not suited for receiving food. The larvee have, at the end of their 
bodies, two long threads, which remain in the perfect Perla, but 
not in the perfect Nemoura; the latter lose the two caudal hairs 
* From yypa, a thread ; and ovpa, a tail.—Eb. 
