204 PEESH-WATEK AQTJAEIA. 



head downwards, and with their posterior legs at right angles 

 to their bodies. Another way to catch them is to sweep with 

 the net, backwards and forwards, the weedy edges of the 

 pond or around the masses of aquatic plants. If the first 

 attempt is unsuccessful, another should be made in an undis- 

 turbed part of the water. These beetles will generally be 

 found in pairs, male and female (Fig. 131). They should not 

 be placed, when caught, in the same yessel with other insects 

 of different kinds, or, notwithstanding the terrors of new 

 captivity, they will be found to have re-commenced their work 

 of destruction before they arrive at their future home. It 



Fig. 131. Dytiscus marginalis (Male and Female). 



wiU be frequently noticed by the hunter for aquarium speci- 

 mens that pieces of water which have supplied certain species 

 of beetles one year will be without them the next, and vice 

 versa. This is accounted for by the power and love of migra- 

 tion which aquatic beetles possess. 



As before suggested, a separate tank should be prepared 

 for D. ma/rginalis. An inverted propagating glass, of lOin. 

 or 12in. in diameter, will do very well ; but a small rect- 

 angular aquarium will do better, for the forms of the beetles 

 as they swim to and fro will then not be distorted. The 

 aquarium should be placed out of the rays of the sun, and 

 not iu too much light, as it wUl not be wise to depend upon 



