The Inhabitants of the Aquarium 287 



brown bristles. These legs and the general 

 shape of the insect make it one of the most 

 rapid swimmers. The male can be distin- 

 guished by the disks or cushions on the fore- 



Fig. 117. Yellow-bordered Water Bee- 

 tle, Dytiscus marginalis, female. 



legs, which serve to fasten the male to the 

 female during the mating process. 



While this beetle stays for a long time 

 under water, either near the bottom or in 

 the vegetation below the surface, it must 

 come up occasionally to take in a fresh sup- 



