
416 THE INSECT WORLD. 
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* 

3 Fig. 384.—Larva of a Fig. 385.—Perla marginata 
bicaudata. Nemoura. (larva). 
(Figs. 883, 384, and 385), which flutter about the banks of rivers, 
and settle on stones, shrubs, and aquatic plants. Their larve are 
naked, without cases, and alwayslive in the water, hiding themselves 
under stones, to watch for small insects, for they are carnivorous. 
One sees them often balancing their bodies, holding on to a pebble. 
They go through the winter, and only become pupz in the spring. 
After moulting, they have the rudiments of wings. Very soon 
afterwards the pupe leave the water, and undergo their meta- 
morphosis. 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 yvnpa, a thread ; and oved, a tail.—Ep. 


