DEATH FEIGNING REACTIONS IN TYCHIUS PICIROSTRIS 149 



tactic in nature is an explanation which in turn needs to be 

 explained, and a positive explanation is not yet forthcoming. It 

 is probably due, however, to some disturbance in the balance 

 of the metabolic processes causing the excessive elaboration of 

 some substance or substances which incite the contraction of 

 the leg muscles. 



The feigning reaction may perhaps be resolvable into two 

 components, one manifested in the flexing of the leg appen- 

 dages, the other in the quiescence of the insect. The fact that 

 it is possible to induce a partial feint in which the insect is per- 

 fectly quiet while the legs are not flexed and, in some cases, 

 after treatment with chloroform, to induce the flexing of the 

 legs unaccompanied by the quiescent state, suggests that these 

 two actions may be the result of separable causes, but the data 

 at hand are too slender for a definite pronouncement on the 

 subject. 



Attention should also be called to the fact that the reaction 

 is segmental and not controlled by the supra-oesophageal gang- 

 lion. The fact that a decapitated insect will not react at room 

 temperature is in no way antagonistic to this view, because the 

 removal of some of the most important trophic centres must 

 necessarily cause some disturbance in the metabolic processes 

 of the nervous system, and the intensity of the stimulus neces- 

 sary to bring about a definite reaction will differ from that 

 necessary under normal conditions; in other words, the thresh- 

 hold of stimulation may be either lowered or raised. One 

 result of this disturbance is manifested in the pendulum and 

 rhythmic movements of the legs of a decapitated weevil, and it 

 it is obvious that this movement cannot coexist with the death 

 feigning reaction as, from their natures, they are mutually 

 exclusive. It will be remembered, however, that cold will so 

 lower the threshhold of stimulation that the decapitated insect 

 will respond readily at low temperature. 



