INSECTS 35 



should be hungry it will hang on, to its victim with a tenacity 

 worthy of a bulldog. In fact the beetle can be lifted out of 

 the aquarium and swung round and round without relinquishing 

 its hold. 



The male and female Dytiscus, though of the same size, are 

 readily distinguished from each other : the former having two 

 disc-like structures on its front legs, which are absent in the 

 female. These discs secrete a sticky, gummy material, with 

 which the male holds the female. This sticky substance is 

 sometimes the cause of a most unenviable position, as the male 

 beetle finds itself otuck to stones, and other objects. The un- 



Young Corixa (one hour old). Larva of Ascilius sulcatus. 



fortunate creature takes some time to get free, and no sooner 

 is this done than it resettles, and the trouble starts again. 

 Thus a beetle may be continually sticking to various objects, 

 much against its wish. The wing-cases elytra which are the 

 first pair of wings hardened, not only protect the membraneous 

 wings, but also act as an air reservoir. For the water-beetle is 

 unable to live on aerated water, and depends entirely on the 

 atmosphere for its supply, and so we will notice that the insect 

 comes to the surface at frequent intervals, and extrudes the end 

 of its abdomen, drawing back the elytra, so as to facilitate the 

 entrance of air, and then, with a supply imprisoned beneath the 

 wing-cases, it swims slowly away and remains below until the 

 store is exhausted. Dytiscus lays her eggs in clefts made in 



