22 



Nitric Oxide, NO. Carahus serratus became unable to 

 crawl the moment it was put in this gas, and in about ten sec- 

 onds was perfectly motionless. It never recovered, although 

 removed at the end of fifteen seconds. Oniscus never survived 

 an immersion of forty to sixty seconds in this gas. All insects 

 killed by nitric oxide became rigid, while the joints of those 

 killed by carbonic dioxide were not stiffened. 



It is quite evident from the preceding experiments that car- 

 bonic dioxide, alone or mixed with air, is poisonous to insects. 

 Carbonic monoxide mixed with air was not tested, but probably 

 is not poisonous, acting only by suffocation. This is the more 

 likely on account of the similarity of its effects to those pro- 

 duced by hydrogen, which is not poisonous, as is shown by 

 insects living in a mixture in which it was substituted for the 

 nitrogen of the air. Again it is probable that carbonic mon- 

 oxide, which poisons vertebrates by solidification of the red 

 blood corpuscles and rendering them incapable of performing 

 their work, would have no effect, except that of suffocation, on 

 insects, whose respiration is performed by direct contact of the 

 air with the muscles, without the intervention of blood corpus- 

 cles. Oxygen seems only to stimulate insects, although in 

 some cases it may produce death in a short time. Nitric oxide 

 evidently acts as a quick poison, from the action of which in- 

 sects do not recover. Geo. Dimmock. 



Proceedings of the Club. 



§ I?). Appendages homologous with Legs. When ex- 

 hibiting a specimen of Dictyopteryx signata, which has two 

 pairs of gills on the under side of the head. Dr. Hagen said 

 that Pictet figures the head of Nemura chierea, which has two 

 pairs of gills on the under side of the head and three on the 

 thorax. Dr. Hagen considers the first two to represent or to 

 be the remains of the legs belonging to the rings of the head. 

 He said further, in connection with Dr. Packard's remarks, 

 given below, that the female organs of Odonata are pleural (as 

 are the legs) ; in Neuroptera and Hemiptera the female parts 



