Habits and Food of Larvae . 49 
spare some Planorbis snails, but devoured them out of their 
shells. 
These voracious larvae lie horizontally, often quite deep 
in the water, and rise and sink gradually and move slowly 
in a horizontal direction, except when darting on their prey. 
When the larvae wish to rise, the head seems more or less 
directed upwards. Now and then they may be seen floating on 
the surface of the water perfectly motionless. 
Fig. 19. 
Larva and pupa of Mochlonyx (after Meinert). 
Moehlonyx larvae. —Mochlonyx larvae seem only to have 
been observed by Meinert, who states that they are even more 
carnivorous than Corcthra , especially attacking larvae and pupae 
of their own kind ; and if such cannibalism is begun in a glass, 
nothing seems able to stop it, and often it ends with the 
vol. i. E 
