Hudson. — On the Senses of Insects. 21 



forks, but they did not disturb her in the least. I then 

 approached the feather of a pen very quietly so as almost to 

 touch first one and then the other of the antennae, which, 

 however, did not move. I then dipped the pen in essence of 

 musk and did the same ; the antenna was slowly retracted 

 and drawn quite back. I then repeated the same with the 

 other antenna. I was, of course, careful not to touch the 

 antennae. I have repeated this experiment with other sub- 

 stances with several ants, and with the same results. Perris 

 also made the same experiments with the palpi, and with the 

 same result ; but if the palpi were removed the rest of the 

 mouth gave no indications of perceiving odours." 



Graber also made a number of experiments, and found that 

 in some cases (though by no means in all) insects which had 

 been deprived of their antennae still appeared to possess the 

 sense of smell. But if, as we have, I think, good reason to 

 suppose, the power of smell resides partly in the palpi, this 

 would naturally be the case. He also tested a beetle (Silplia 

 thoracica) with oil of rosemary and assafoetida. It showed its 

 perception by a movement in half a second to a second in the 

 case of the oil of rosemary, and rather longer — one second to 

 two seconds -in the case of the assafoetida. He then de- 

 prived it of its antennae, after which it showed its perception 

 of the oil of rosemary in three seconds, on an average of 

 eleven trials ; while in no case did it show any indication of 

 perceiving the assafoetida, even in sixty seconds. 



This would seem to indicate a further complication— not 

 only that both the antennae and the palpi may possess the 

 sense of smell, but also that certain odours may be per- 

 ceived by the former, and others by the latter. As regards 

 flies (Mn sea), Forel removed the wings from some blue- 

 bottle flies and placed them near a decaying mole. They im- 

 mediately walked to it, and began licking it and laying eggs. 

 He then took them away and removed the antennas, after 

 which, even when placed close to the mole, they did not ap- 

 pear to perceive it. 



Plateau also put some food of which cockroaches are fond 

 on a table, and surrounded it with a low circular wall of card- 

 board. He then put some cockroaches on the table. They 

 evidently scented the food, and made straight for it. He then 

 removed their antennae, after which as long as they could not 

 see the food they failed to find it, even though they wandered 

 about quite close to it. 



On the whole, then, the experiments which have been 

 made seem clearly to prove that in insects the sense of smell 

 resides partly in the antennae and partly in the palpi. This 

 distribution would be manifestly advantageous. The palpi 

 are more suited for the examination of food, while the an- 



