28 HENRY H. P. SEVERIN AND HARRY C. SEVERIN 



and probably in Amaurobius sp.) and it is a rhythmically inter- 

 rupted tetanus." Holmes (12, p. 211) in his work on Ranatra 

 concludes that "it is abundantly evident that the removal of 

 the supra-oesophageal ganglion causes a marked diminution of 

 the duration of the death feint." 



19. General features of the nervous systems of Belostoma flum- 

 ineum and Nepa apiculata: The nervous system of Belostoma 

 fiumineum and Nepa apiculata is somewha,t similar to that 

 which we (19) have described and figured for Ranatra. The 

 supra-oesophageal ganglion is situated in the upper posterior 

 part of the head and is closely connected with the infra-oesoph- 

 ageal ganglion by the circum-oesophageal commissures. Near the 

 anterior margin of the prothorax lie the fused infra-oesophageal 

 and first thoracic ganglia (fig. 7, in). Packard (20, p. 226) also 

 describes a fusion of the sub-oesophageal ganglion with the first 

 thoracic, in Acanthia, Nepa and Notonecta. As in Ranatra, 

 the rest of the ganglionic system of Belostoma and Nepa con- 

 sists of a large ganglion situated mostly within the mesothorax 

 but extending backward also into the metathorax. 



20. Shock effect of decapitation: In snipping off the head of 

 Belostoma or Nepa, only the brain is removed. A quick, sharp, 

 clean cut was made with a pair of fine scissors in all of the follow- 

 ing mutilation experiments. When the head was removed from 

 feigning Belostomas lying on their backs, the insects, with but 

 few exceptions, came out of their inert state immediately. Of 

 the small number that maintained the immovable state, some 

 would keep the usual death-feigning posture for a few seconds 

 while others would do so for a somewhat longer time. 



As a general rule, most of the decapitated Belostomas showed 

 a marked shock effect. They would usually move all their legs 

 vigorously after the head was severed from the body, but did 

 not often succeed in righting themselves. Some were placed on 

 their backs in a glass dish with the bottom either covered with 

 water or moist blotting paper and yet most of these failed to 

 right themselves for days; others, however, would assume the 

 normal righted position very readily. When the cover of the 

 glass dish was raised, the decapitated individuals lying on their 

 backs would often respond by moving their legs. 



In one set of experiments, six Belostomas were beheaded and 

 placed upon their backs in direct sunlight at a temperature of 



