46 THE COCKROACH : 



concerning its immediate surroundings. Long antennae, such 

 as those of the Cockroach, are certainly organs of touch, but it 

 has been much disputed whether they may not also be the seat 

 of some special sense, and if so, what that sense may be. 

 Several authors have found reason to suppose that in the Insect- 

 antenna resides the sense of hearing, but no evidence worth the 

 name is forthcoming in favour of this view. Much better 

 support can be found for the belief that the antenna is an 

 olfactory organ,* and some experiments which seem conclusive 

 on this point will be cited in a later chapter. 



In the Cockroach the mandibles and maxillae are the only 

 important instruments of mastication. The labium is indirectly 

 concerned as completing the mouth behind and supporting the 

 lingua, which is possibly of importance in the ordinary opera- 

 tions of feeding. Plateauf has carefully described the mode of 

 mastication as observed in a Carabus, and his account seems to 

 hold good of biting Insects in general. The mandibles and 

 maxillae act, as he tells us, alternately, one set closing as the 

 others part. The maxillae actually push the morsel into the 

 buccal cavity. When the mandibles separate, the head is 

 slightly advanced, so that the whole action has some superficial 

 resemblance to that of a grazing quadruped. 



The palps of the maxillae and labium have been variously 

 regarded as sensory and masticatory instruments. Not a few 

 authors believe that they are useful in both ways. The question 

 has lately been investigated experimentally by Plateau, f who 

 finds that removal of both maxillary and labial palps does not 

 interfere either with mastication or the choice of food. He 

 observes that in the various Coleoptera and Orthoptera sub- 

 mitted to experiment the palps are passive while food is being 

 passed into the mouth. 



Plateau's experiments are conclusive as to the subordinate 

 value of the palps in feeding. The observation of live Cock- 







* Rosenthal, Ueb. d. Geruchsinn cler Insekten. Arch. f. Phys. Reil u. Autenrieth, 

 Ed. X. (1811). Hauser, Zeits. f. wiss. Zool., Bd. XXXIV. (1880). 



t Mem. Acad. Roy. de Belgique, Tom. XLI. (1874). Prof. Plateau's writings will 

 often be referred to in these pages. We owe to him the most important researches 

 into the physiology of Invertebrates which have appeared for many years. 



J Exp. sur le Role des Palpes chez les Arthropodes Maxilles. Pt. I. Bull. Soc. 

 Zool. de France, Tom. X. (1885). 



