Effects of certain Agents on Insects. 203 



slightest motion of any part was seen afterwards. Taken out, 

 after having been in the tube ten minutes, it did not revive on ex- 

 posure to the air. The same day repeated the experiment on 

 another honey bee : after a few minutes of restlessness it fell down 

 motionless. Taken out, after about eight minutes, and exposed 

 to the air, in about half an hour a languid motion of the abdomen 

 was visible, and the same was occasionally seen to occur for about 

 thirty hours, soon after which time it was found motionless and 

 dead. The proportion of sulphuretted hydrogen mixed with the 

 atmospheric air in this instance was very minute. The experi- 

 ment repeated under the same circumstances with another active 

 honey bee. The result was similar, — the state of torpor, the 

 effect of the very dilute gas, was, on exposure to the air, followed 

 by slight signs of revival, soon terminating in death. 



Sulphurous Acid Gas. — On the 24th of January exposed a fly 

 (Heteromyza buccatd) to this gas, very much diluted, by kindling 

 a minute portion of sulphur under a wine glass, in which the fly 

 was confined. In a few seconds it tottered and fell, and in a few 

 more became motionless ; it did not recover on exposure to the 

 air. 



Chlorine. — On the 22nd January exposed a fly of the same kind 

 as the last to this gas, as disengaged in the tube by the action of 

 dilute sulphuric acid on a mixture of common salt and black oxide 

 of manganese. In less than two minutes the fly became motion- 

 less. Taken out immediately and exposed to the air, it did not 

 revive. 



3. On the Action of Vapours. 



Ammonia. — On the 3rd January put a fly {Heteromyza buccata) 

 into a tube, with a few drops of strong aqua ammonice. At first 

 it was active and i*estless ; in about half a minute it fell down, 

 moving its legs ; in another half- minute it was motionless. It had 

 not come in contact with the fluid. Taken out it did not revive. 



Exposed another fly (Musca lanio) in the same manner to the 

 ammoniacal vapour ; it presently exhibited convulsive movements ; 

 in less than a minute it was motionless, and it remained so, for 

 several hours, after exposure to the air ; the following morning, it 

 was found revived and active. 



Muriatic Acid. — Exposed a fly of the same kind to the vapour 

 of strong muriatic acid : during the first half-hour the fly was 

 active, it gradually became less so ; after about two hours it was 

 found motionless. Taken out of the tube, after showing no signs 



