■21 



Cakbonic Monoxide, CO. This gas, so poisonous to man, 

 was tried on a few species of insects with the following results. 



I omitted, unfortunately, to note the sex of the Pieris rapae 

 used, and sex may have considerable to do with the very differ- 

 ent time required to prostrate the first two and the last two 

 specimens. They all rubbed their probosces about their legs 

 while recovering, and several of the species which were im- 

 mersed in carbonic monoxide exhibited a slight tendency toward 

 paralysis of the posterior limbs during recovery. 



Hydrogen, Ho. Pieris rapae was rendered motionless by 

 immersion in the gas in thirty seconds. It was taken out at 

 the end of five minutes, and began to move at the end of eight 

 minutes. At the end of ten minutes it was flying in a weak 

 manner. Harpalus ealigiyiosus was rendered motionless in 

 forty seconds, was removed in five minutes, moved its feet and 

 antennae at the end of six minutes, acted as if very weak for 

 ten or twelve minutes more, but crawled off, apparently as well 

 as ever, at the end of that time. 



In a mixture of eighty parts of hydrogen and twenty parts 

 of oxygen, and in a mixture of fifty parts of hydrogen and 

 fifty parts of oxygen, Pieris rapae showed no signs of weakness 

 at the end of thirty minutes. 



Oxygen, O2. Silpha novehoracensis Forst. QS. marginalis 

 Fab.) became slightly more active upon being placed in oxygen. 

 The sexes copulated, and did not seem to be disturbed by the 

 change of atmosphere. Staphylinus maculosus remained in 

 oxygen three days without any apparent change in health or 

 habits. 



A spider placed in oxygen began to show signs of weakness 

 in about forty minutes, and at the end of an hour was so Aveak 

 as to be scarcely able to tarn over when placed on its back. 

 Upon removal to the air it soon recovered. 



