1904.] NATURAL SCIENCES OF PHILADELPHIA. 645 



was rubbed. Some idea of the delicacy of these reactions may be 

 gained from the fact that ants in a Petri dish resting on a pine table-top 

 reacted to the scratch of a pin on the table at a distance of ten feet 

 from the dish. A measure of the stimulus necessary to call forth the 

 most delicate reaction, usually a jerking movement of the antennae, was 

 obtained in the following way : A small artificial nest was built on the 

 end of a long board clear of knots and, after the ants had become ac- 

 customed to their nest, stimuli were introduced by dropping a shot 

 weighing half a gram on the board at different distances from the nest 

 and from different heights. It was found that the ants reacted to a 

 blow given to the board 4.3 metres (14 feet) from the nest when the 

 shot fell from a height of 15 centimetres (6 inches), but that they did 

 not react when it fell through only half that distance. 



Ants not only react to material \Tibrations received through wood, 

 glass, water, etc., but they will also react to such vibrations when 

 resting on a bit of sponge in an artificial nest or on the soil in which they 

 construct their nests. Thus ants within their natural earth nests may 

 be stimulated by the vibrations of the material on which they stand, 

 though they will not respond to similar vibrations in the air about 

 them. 



To ascertain what parts of the body of the ant are concerned in its 

 reaction to the vibrations of non-gaseous materials, we performed 

 experiments on a number of individuals of Stenamma fulvum piceum 

 that had been deprived of portions of the body. 



All the mutilated ants, except those lacking heads or abdomens, had 

 undergone the necessary surgical operations so long as three or four 

 weeks previous to the experiments, and had therefore had time for 

 full recovery from shock-effects. 



The irritability of workers deprived of their funicles, or of the whole 

 of the antennae, was such as to make it necessary to isolate each in 

 order to prevent mutual slaughter, though all were of the same colony. 

 This irritability continued even after they had recovered from shock- 

 effect, had become alert and active, and had been more than a month 

 without funicles, or without both funicles and scapes. Queens similarly 

 mutilated were scarcely more irritable than when in normal condition, 

 and nearly all of the thirty operated upon survived the operation 

 more than two months and laid eggs. 



Queens and workers deprived of only one antenna were no more 

 irritable than normal ants, and hardly any deaths resulted from this 

 mutilation, while not more than twenty per cent, of the workers survived 

 the loss of either both funicles or both antennae. 



