OBSERVATIONS ON YOUNG OF RANATRA OUADRIUENTATA l6l 



very often found swimming on the side of the dish towards the 

 light ; if the dish is turned about they quickly swim back again 

 to the light side. When out of water they are comparatively 

 irresponsive to light a fact in marked contrast to the behavior 

 of the mature insects. Movements of the head in response to 

 changes in the position of the light, which are so pronounced in 

 the adults are manifested in the young of a week old or even 

 less, but they are not very pronounced. When out of water the 

 young could not be induced to walk toward the light or respond 

 to it in any other way than by making rather feeble movements 

 of the head. While contact stimuli applied to the mature insects 

 when in the water cause a negative phototaxis, they failed in the 

 forms experimented with to produce this effect in the young. 



The death feigning of young Ranatras is not so decided or pro- 

 longed as in older specimens, and it also differs in certain other 

 particulars. Young Ranatras when taken out of the water and 

 laid on a table frequently become immobile in whatever position 

 they may happen to lie. Neither in the young nor the mature 

 form do the appendages assume any definite position such as they 

 do in the death feint of many other insects. The feint is shown 

 during the first day of free life. The muscular system gives evi- 

 dence of a certain degree of rigidity, but owing to the flexibility 

 of the appendages this is not so clearly manifested as in some- 

 what older individuals. 



In specimens five days old the death feint is more decided. Sev- 

 eral specimens of this age were taken out of a dish and laid on a 

 table. Immediately they all became immobile. They could be 

 picked up by one of the slender legs and held out without caus- 

 ing a bend in any of the joints, thus showing that the muscles 

 were in a state of extreme contraction. Many specimens would 

 endure considerable handling and poking about without making 

 any response. In some cases such treatment would bring them 

 quickly out of the feint, and all the forms experimented with were 

 brought out of it by more prolonged stimulation. In this respect 

 the young differ from the mature insects which will endure a 

 great deal of maltreatment without making any response. 



In specimens coming out of the death feint handling or rubbing 

 them with a dry camel's hair brush produced in some cases a 



