112 INSECTS COLEOPTEKA DIAGRAM 6. 



The Dytiscidoe swim, and pass part of their life in the water. 

 For this purpose, they have flattened legs, shaped like oars. 

 But they are obliged to come to the surface frequently in order 

 to breathe the air, a store of which they always keep under their 

 elytra, when diving to the botton of the water. They are es- 

 sentially carnivorous animals, and even attack newts, and devour 

 them alive. In the evening, they leave the water, spread their 

 wings, and fly about. They then fly into rooms, attracted by 

 the light. When touched, they exude from the surface of their 

 body an oily liquid, as white as milk, and extremely fetid. The 

 larvae live constantly in water, and are carnivorous like the per- 

 fect insect. They have pointed mandibles which cross each other, 

 with which they can pinch severely. 



The Gyrinidw are small insects which are seen twisting round 

 like drops of quicksilver on the surface of ponds, where it is very 

 difficult to catch them, They are popularly called whirligig 

 beetles. Their back is black, but is so highly polished as to re- 

 flect the light of the sun like a metal button. 



The HydropMUdw somewhat resemble the Dytiscidse in form 



and habits, but are much larger. 

 These are our largest native water- 

 insects. Like the Dytiscidse they 

 pass the day in ponds. They swim 

 and fly very well, but walk with 

 difficulty. They can remain under 

 water for a long time, but are never- 

 theless obliged to come to the sur- 

 face from time to time to breathe. 

 In the evening, they fly about. 

 Their larva are very large, black 

 and wrinkled, and swim with ease. 

 They live exclusively in the 

 water. They are extremely vora- 

 cious. They are also remarkable 

 for their habit of making themselves 

 HydrophUue, male. soft and flaccid, as if dead, when 



