294 Fresh Water Aquarium 



when a fly, a crumb of bread or some other 

 edible body is thrown into the swarm, — 

 when the circling' ceases and they all rush 

 frantically upon the prey, each eager to par- 

 ticipate in the feast, only to resume their 

 play as soon as the last vestige of the food 

 has been disposed of. The slightest dis- 

 turbance in the water or any other apparent 

 danger from the outside will cause a general 

 stampede. With lightning rapidity every 

 single beetle will disappear under the sur- 

 face. After the danger is past, one by one 

 they will gradually reappear on the surface, 

 to gather again for the interrupted sport. 

 They love the sunshine and prefer to spend 

 dark or rainy periods near the bottom. As 

 it is easy to feed the Gyrinus on small insects 

 and plants, they can be kept to advantage 

 in the aquarium, where their graceful and 

 ceaseless play will be interesting and enter- 

 taining, but as, like most water beetles, they 

 like to fly off during the night, a close 

 meshed cover should be provided. 



