Effects of certain Agents on Insects. 211 



Placed the small tube containing the prussic acid instantly after 

 the experiment on the bee under another wine glass, in which was 

 confined a Bombus (B. hortorum), just caught, and very active. 

 During the first minute or two its wings were in constant motion ; 

 during the next four or five it moved about in an irregular 

 manner, its legs alone acting ; in about ten minutes motion 

 ceased, except a slight tremulous one of the legs ; — now several 



parasitical insects (Acarus ?) dropt from it, deprived of motion 



themselves ; in about twenty minutes it was altogether motion- 

 less. The tube taken out and weighed was found to have 

 sustained no appreciable loss ; it was replaced under the wine 

 glass. In about three hours, though still confined under the 

 wine glass, the humble bee began to revive, and the following 

 morning it was pretty active ; none of the parasitical insects re- 

 vived excepting one. 



Placed another Bombus under a wine glass, with the small tube 

 charged with *08 grains of prussic acid. In less than a minute 

 it was motionless, as were also two or three of the parasitic 

 insects (the same kind as the preceding), which fell from it when 

 the poison began to take effect. In less than two hours it had 

 tolerably revived. Now added a single drop of the acid, in about 

 ten minutes the humble bee, after being slightly convulsed, became 

 motionless. On the following morning it was found alive, moving 

 its feet feebly. 



Substituted for the small tube one a little larger, its mouth 

 two-tenths of an inch in diameter, its capacity one-tenth of a 

 cubic inch. After pouring into it 7 grains of prussic acid, it was 

 suspended by a thread in the larger tube, and so used in the fol- 

 lowing trials. 



Introduced a large vigorous beetle (Geotrupes stercorarius), 

 and closed the receiving tube with a cork so as to prevent the 

 escape of the vapour of the dilute acid. In about a minute the 

 beetle became motionless. Taken out after two hours and a 

 quarter it was found dead. 



Next introduced an active Bombus. In a few seconds it became 

 motionless — entirely motionless. Taken out after an hour it 

 exhibited no signs of revival ; it was dead. 



Introduced another active Bombus. It too in a few seconds 

 was rendered motionless. Taken out after about a minute, it 

 showed no signs of revival for many hours ; but the following 

 morning it was found tolerably revived. Replaced in the tube 

 with the acid, and left there three hours, it did not recover when 

 taken out. The tube, now weighed, was not found to have sus- 



p 2 ' 



