76 THE BIOLOGY OF INSECTS 



students. N. E. Mclndoo (191 6) has, however, given some 

 reasons for doubting whether the so-called gustatory sense 

 of insects can really be distinguished from their sense of 

 smell. Such discussions illustrate the uncertainty which 

 must surround our conceptions of an insect's conscious 

 sensations, and indeed many physiologists regard our own 

 discrimination of flavours as referable to smell rather than to 

 taste. But there can be no doubt that the minute structure 

 of sense-organs of this type indicates clearly that they are 

 adapted for receiving chemical stimuU such as those which 

 give rise to normal sensations of smell and taste, and there 

 are many recorded experiments and observations on the 

 reactions of various insects which afford support to this 

 opinion. 



On several occasions A. Forel (see 1908, pp. 73 f.) 

 performed experiments which appear to prove the presence 

 of definite olfactory nerve-endings in insects' feelers. Ants 

 recognise members of their own communities by smell, and 

 as they approach one another their feelers are constantly 

 moving ; when these appendages are removed ants were 

 found to distinguish no longer between sisters and strangers. 

 Female flies of the bluebottle group lay their eggs on the 

 flesh of dead animals, and there is no doubt that the approach 

 to a carcase for the purpose of egg-laying is a reaction to the 

 olfactory sense. Forel found that if the feelers of such flies 

 be removed they lose the power of locating the objects on 

 which they lay their eggs, while a fly, thus mutilated, and 

 actually placed on a putrid mole did not at once lay eggs 

 thereon as a normal female would have done. From such 

 results it appears that the approach to a suitable breeding 

 place, and the laying of the eggs thereon, are alike actions 

 reflex to the reception of olfactory stimulation. Burying 

 beetles (Silphidae) not only lay their eggs on dead animals, 

 but themselves feed on such carrion. In these beetles the 

 terminal segments of the feelers are thickened so as to form 

 a club, and the removal of the clubbed tips of the feelers 

 rendered the beetles incapable of finding their food and 

 breeding-material. Further, a male Silkworm Moth {Bombyx 



