BEHAVIOUR loi 



busy bee " are indeed mostly " of an automatic kind." The 

 segmentation of the central nervous system in insects is a 

 structural feature which suggests imperfect integration of 

 nerve-action, and consequent imperfect individuality, and 

 observ^ations following mutilation, whether deliberate or 

 accidental, convince us that there is considerable exercise 

 of independence between various parts of an insect's body. 

 In a trisected wasp, for example, the jaws and mouth con- 

 tinue to feed and the thorax to walk, while stimulation of 

 the abdomen by a careless observer may lead to unpleasant 

 demonstration that the sting will act as the result of a reflex 

 conducted through the abdominal nerve-centres without 

 possibility of reference to the brain. 



Insects of various orders have the habit known generally 

 as " death-shamming " ; when touched or handled they lie 

 motionless on the back with the limbs strongly flexed. 

 This is a reaction to contact with certain objects, whereof 

 a human hand is one. H. H. P. and H. C. Severin (191 1), 

 who have carefully studied such reactions in aquatic bugs 

 (Nepa and Zaitha), conclude that the contact-stimulus works 

 so as to bring the muscles into a state of intense contraction 

 — a kind of prolonged tetanus. " Nepa, while feigning 

 death, may be taken by any tibia or femur and held in a 

 position so that the weight of the entire body is borne by 

 the extensor muscles of a single segment of one leg." 

 Here the head nerve-centres appear to exercise an inhibitory 

 power over the muscles while the reaction lasts, for if a 

 death-feigning Nepa be beheaded, the muscles immediately 

 relax, while if the insect be bisected across the thorax the 

 hmbs in front of the cut remain flexed while those behind 

 it relax. This term *' death-shamming " has been commonly 

 applied to this habit because it has often been regarded as a 

 voluntary and purposeful method of behaviour adopted by 

 the insect in the presence of some recognised danger with 

 the object of securing safety. There seems no reason, 

 however, for regarding it as anything beyond a simple 

 automatic reflex, which may in some cases serve as a pro- 

 tection to the creature that adopts it. 



