72 



NATURE STUDY 



covers readily finds its way into the beetle's body. The water- 

 scavenger beetle carries most of its air supply on its under or ven- 

 tral surface, where it is held in a lot of fine short hairs. The air 

 gives the under side of the beetle a shining silvery appearance. 

 The air is held by the fine hairs by virtue of the surface film. If 

 you dip a bit of cloth having a pile, as velvet, into water, you 

 will see that it retains underneath the water a nearly complete 

 coating of air. The under side of the water-scavenger beetle is 

 covered in places with a fine pubescence which acts as the pile of 

 the velvet does. 



Kill one of the beetles and examine it. How many wings 

 has it ? Note that the hind wings, which are larger than the 

 front wings and are thin and membraneous, are folded both longi- 

 tudinally and transversely underneath the stiff, horny fore wings. 

 The hind wings are the true flying wings, the fore wings being 

 chiefly used as a firm protecting covering for the hind wings when 

 the beetle is in the water. Altho the water-beetles live naturally 

 in water, they are provided with 

 wings w-ith which they are en- 

 abled to escape from a drying 

 pond or from a pond which be- 

 comes over stocked with their 

 kind. 



There are two kinds of water- 

 bugs as well as two kinds of 

 water-beetle.s. Some of the bugs 

 swim with back downward, i. e. , 

 upside down, and are called back- 

 swimmers; the others swim in 

 normal position with back upper- 

 most and are called water-boatmen, 

 also, in their markings, the water-boatmen (fig. 45), hav- 

 ing the back greenish gray with a fine black mottling, 



Fig. 44. A. Back-swim iiier (.\,'fonr^fa). 



The two kinds differ. 



