398 CHRISTINE ESSENBERG 



spring they emerge, lay eggs along the edge of grasses growing 

 under water but near the surface, fastening them with a water- 

 proof glue. The eggs hatch within three weeks. 



These insects move backward and forward with equal facility, 

 though the usual direction of locomotion is forward; but if the 

 animal is approached from the front it moves backward very 

 swiftly. It can also float on its back as has been observed 

 taking place in the aquarium during and after the cleaning 

 process of the insect, when it lies on its back for a considerable 

 time and is carried by the water, moving its legs or else keeping 

 perfectly quiet. When disturbed while on the water the insects 

 betake themselves quickly to the land or among the weeds, and 

 hide by clinging to the lower surface of the leaves or by lying 

 quietly on the ground. 



For its food supply the water-strider depends upon such living 

 or dead insects as it finds floating on the surface of the water. 

 Sometimes it catches mosquitoes flying above the water. In 

 the latter case it sits quietly upon some aquatic plant and, as 

 soon as the mosquito approaches, makes a swift leap and catches 

 the insect, or when a mosquito is discovered at some distance 

 on the surface of the water, the water-strider moves very 

 swiftly towards it until it reaches its victim, when it seizes it 

 with its raptorial forefeet. The food is never taken from under 

 the water. Several individuals were kept in an aquarium 

 thickly populated with mosquito larvae, although the insects 

 had not received any food for several days and were in a starv- 

 ing condition, they did not touch the mosquito larvae, but as 

 soon as a mosquito emerged from the pupa case it was caught 

 and eaten. Gerris remiges is very voracious and will eat any 

 animal matter, not disdaining its own kind. It does not hesitate 

 to attack animals many times its own size. In the aquarium, 

 where there is less chance of escape, the young nymphs usually 

 fall victims to the adults, and the stronger ones, as a rule, feed 

 upon their weaker companions. In the laboratory the water- 

 striders were fed mostly upon flies, they being most easily ob- 

 tained, but they ate other animal matter, such as ants, bees, 

 butterflies, moths, Jerusalem crickets, etc. Gerris remiges is 

 not particular in its choice of food and its sense of taste is not 

 well developed. Upon different occasions the insects were fed 

 flies, some of which had been previously soaked in quinine and 



