206 Dr. John Davy on the 



kind at the temperature of 54°; the immediate effect was the 

 same, in a few seconds it had lost the power of walking on the 

 perpendicular side of the glass tube, and was more restless than 

 before ; accidentally a small portion of its surface came in contact 

 with the oil, in less than half a minute it became motionless : im- 

 mediately taken out it did not revive. The experiment repeated 

 on another fly of the same kind, not allowed to come in contact 

 with the oil ; it became motionless in a minute, after having been 

 instantly affected in the same manner as the preceding ; taken out, 

 after about two minutes, it did not revive. Repeated the experi- 

 ment on a small fly. 



Strong Acetic Acid. — A fly (Heteromyza buccata), exposed to the 

 vapour of this acid at about 56°, was not immediately apparently 

 affected, nor after five hours ; after ten hours it was found motion- 

 less ; it did not revive when taken out. The trial was repeated 

 on another fly of the same kind, with a like result, and also on a 

 gnat ; in about five minutes it became motionless ; taken out, 

 after about two hours, it was found to be dead. Repeated it on 

 another fly {Heteromyza buccata), in about half an hour it ceased 

 to move ; allowed to remain in about two hours, it did not revive 

 when taken out. 



Attar of Roses. — Placed a fly {Heteromyza buccata) under a 

 wine glass, with a portion of paper on which a drop of this 

 essential oil had been let fall ; temperature of the room 54°. At 

 first the fly did not appear to be affected ; in about an hour it had 

 become dull, moving languidly ; five hours after it was found mo- 

 tionless. Taken out it showed marks of revival in about half an 

 hour ; after three hours it had recovered its activity. Repeated 

 the experiment on a small fly — a gnat ; after an exposure of about 

 two hours it was found motionless ; taken out it did not revive. 



Music. — Placed a fly {Heteromyza buccata) under a wine glass 

 with a portion of this substance, adding a few drops of water to 

 favour the rise of the odorous effluvia. After twelve hours no 

 appreciable effect was produced ; the activity of the insect was 

 not impaired. Repeated the experiment on a gnat and another 

 fly, the species of which was not determined, and with a similar 

 result; one was exposed to the odour for twelve hours, the other, 

 the latter, for twenty-four : this insect, on lifting up the glass, took 

 wing and escaped. 



Iodine. — Exposed a fly {Musca domestica) to the vapour of this 

 substance at 70° ; the air in the tube was only just perceptibly 



