400 CHRISTINE ESSENBERG 



surface, or by holding it down and pressing on the dorsal surface. 

 The first sign of death feigning is usually the crossing of the 

 forelegs, then the body becomes rigid and the legs are drawn 

 up close to it so that the whole body assumes a compact shape. 

 The water-strider has been made to assume this position thirteen 

 times in succession. Later it did not so readily respond to the 

 stimulus and the successive periods of death feigning gradually 

 decreased in length, the first periods lasting for from twenty-six 

 to twenty-five minutes and the last periods lasting for from six 

 to five minutes, only. The larvae of these insects are especi- 

 ally prone to feign death. When taken from the water they 

 sometimes feign death and do not recover for an hour or longer. 

 Feigning death is evidently not a voluntary act on the part of 

 the animal, this condition being brought about by some physi- 

 ological change. Professor S. J. Holmes cites similar experi- 

 ences with Ranatra jusca also with some birds from which he 

 pulled feathers while the birds were in this condition without 

 producing any response. 



Gerris remiges is positively phototactic. If it takes to its 

 wings once in a while it always flies toward the light, producing 

 a buzzing sound as it flies. When placed in an aquarium it 

 swims toward light. It is more phototactic in strong light and 

 in high temperature, less so in a weaker light. 



Gerris remiges is negatively geotropic. If an individual is 

 left in an empty jar it always crawls upward. If placed on 

 the wall it crawls upward, never downward, although it may 

 jump or fly to the ground. The same is true when it retires to 

 sleep on plants, attaching itself to the lower surface of the 

 plants, with head pointing upward. Although very swift of 

 motion when on water, the insect remains perfectly motionless 

 on plants and makes no effort to escape when picked up. Blind 

 individuals act in the same way as do the normal ones in regard 

 to geotropism, i.e., they crawl upward or opposite to the source 

 of gravity. 



Water-striders are positively thigmotactic, piling up in three 

 or four layers, sometimes becoming so tangled up in their long 

 legs that it becomes difficult for those in the middle to disen- 

 tangle from the others. They also crowd together when fright- 

 ened and when hibernating in the winter. 



The water-striders are positively rheotactic and always swim 



