WELCH J HATER IX SECTS 187 



water plants and floating leaves. Handle the larvae carefully as 

 they are easily killed. These insects are easily kept in the aquar- 

 ium. Do not put larvae and adults into the same jar. Feed the 

 adults on bits of raw meat, larvae, on insects, water worms, or 

 small pond snails. Be careful to keep the aquarium as clean 

 as possible and keep it covered since the adults may fly out at 

 night. Put only one larva in a large jar and feed on the same 

 food as the adult. 



The Water Scavenger Beetles (Fig. 11). 



At any time from March to November these large, oval, 

 blackish beetles may be found in the same streams and ponds 

 with the Diving Beetles. At first sight they resemble the Diving 

 Beetles, but differ from them in having no yellow on the body, 

 in hanging with the head at the surface of the water instead of 

 the tip of the abdomen, and in moving the swimming legs alter- 

 nately instead of at the same time. They feed largely on plants 

 and decaying matter. These insects often leave the water and 

 fly about at night. They are attracted to light and the street lights 

 are often visited by them. The eggs are laid in a sort of silken bag 

 which has a stalk at one end. This bag is usually attached to some 

 floating leaf or stem. The larvae (Fig. 22) are somewhat like 

 those of the Diving Beetles in appearance as well as in food habit, 

 since these larvae feed on the smaller animals of the pond. They 

 pass the pupa stage in a sort of cell in the ground outside of the 

 water. To collect these insects, use the same methods as are sug- 

 gested for the Diving Beetles. For the full-grown insects the 

 aquarium must contain water plants. Feed the larvae with 

 smaller water insects. 



The Backswimmer (Fig. 15), 



Another form which appears early in the Spring is the Back- 

 swimmer, and one may expect to find it in any pool or stream 

 which contains vegetation. It can be recognized in the water by 

 the fact that it always swims upside down. The back is shaped 

 like the bottom of a boat and the flattened hind legs, which are 

 much longer than the others, act as oars. The colors are usually 

 black and creamy white. It will be noticed that the Backswimmer 

 comes to the surface frequently. But why? This insect has to 

 breathe the free air and therefore it must come to the surface 

 occasionally for a fresh supply. As it swims down from the sur- 

 face the back part of the body has a silvery appearance which is 

 caused by the air clinging to the body and under the wings, be- 

 ing held there by fine hairs. This is the supply of air which the 



