SMELL. 225 



Previous experience is not necessary to successful flights; 27 successful returns out 

 of 96 were made by wasps used for the first time, but only 1 out of 16 wasps that had 

 previous flights made a successful second trip. Not one of the 17 males returned 

 to their former nests, even though the distance for 16 of them was only one-eighth mile. 

 The function of the antenna? is not the sole factor in bringing them home, for out of 

 24 mutilated wasps, 18 successfully returned. Thus, by the elimination of other 

 faculties, the evidence grows stronger that vision is the sense whereby the insects 

 regain their homes." 



SMELL. 



Sense of smell in insects deprived of antennae. — Forel (1886:184) in- 

 sisted that the experiments of Graber (1885) with strong odors merely 

 proved whether these were irritating or not to the insects concerned and that 

 evidence of smell could be obtained only by causing the insect to recog- 

 nize a certain substance and especially to distinguish it from others in 

 a constant and indubitable manner. As an example, he cited the case of a 

 swarm of males of Saturnia carpini that besieged the window of his room 

 after some females had hatched out, which he regarded, together with many 

 previous observations of others, as demonstrating in insects a special 

 sense that corresponds to that in man. Further demonstration may be 

 furnished by the removal of the antennae whenever the loss of these or- 

 gans carries with it the loss of the sense of smell, as proved to be the case 

 in many of the experiments he carried out. 



When the antennae were removed from individuals of four different 

 genera of ants, they mingled readily without harming each other, and they 

 recognized honey only when the mouth touched it by chance. If the an- 

 tennas were removed in Formica fusca and the ants placed in a globe with 

 their larvae, cocoons, and soil, they did not attempt the slightest digging 

 or give the larvae the least care. When ants of another species were added, 

 they did them no harm, but when the anterior tarsi were cut off above 

 the spine in the same species, they immediately killed other ants given 

 them, and made futile efforts to dig and to care for the larvae. A repetition 

 of these experiments eight years later gave similar results, except in the 

 case of Myrmica ruginodis, which killed other ants as well as its own kind. 

 In the case of Sarcophaga vivipara with both eyes excised, the female readily 

 found a dead mole on which it fed, but after the antennae were removed, 

 it paid no more attention to the mole, even when placed beside it. A blue 

 fly which also fed upon the mole and deposited eggs in it paid no attention 

 whatever to it after the antennae had been removed, in spite of the use of 

 its eyes. Two other individuals of Sarcophaga behaved in similar manner, 

 while a very active Lucilia caesar, though placed on the mole, ceased eating 

 and depositing eggs as soon as the antennae were gone. In like manner, 

 beetles of several genera were unable to rediscover putrid objects after the 

 removal of the antennae. Males of Bombyx mori, which perceived the fe- 

 males at a distance and ran to them directly, were no longer able to deter- 

 mine the direction of the female after the antennae had been removed. 



In an experiment with a wasp, Polistes gallicus, three individuals were 

 employed, one having the antennae removed, the second the front of the 

 head with the sense-organs of the mouth, and the third was left intact. 

 In repose the latter was able to recognize honey at a distance of a centi- 



