The Inhabitants of the Aquarium 293 



in regular rows or layers. To steady this 

 receptacle or nest and keep it in an even 

 position, the pointed part is filled with air. 

 After two weeks the larvae leave the eggs, 

 but remain within the sheltering cover until 

 strong enough to take care of themselves 

 when, by a general effort they burst open 

 their balloon-like home and scatter. 



The Whirligig {Gyrinns natator) inhabits 

 our ponds and streams and is one of twelve 

 to fifteen species. The majority are steel 

 blue and it is very difficult to classify them 

 without careful study and observation. As 

 soon as the ice disappears and the sun begins 

 to warm the water, the Whirligig appears, 

 one of the first of all aquatic insects to en- 

 liven the otherwise dead surface, a certain 

 and never failing sign that spring is com- 

 ing. In swarms they appear, each single 

 beetle circling around by itself with great 

 rapidity and with hardly any pause. It is 

 very interesting to watch the insects in their 

 graceful and endless play, only disturbed 



