IXSECTA. 25 



The tongue may be regarded as the sternal plate of the 

 ring bearing the first pair of maxillae, which has become 

 greatly modified to form an organ of taste. It is homol- 

 ogous in position with the small sternal plate which bears 

 the metastoma in the lobster. (See Guide No. VII., p. 30, 

 Fig. 9^, lb7n, sternal plate, mt, mt\, metastoma.) The 

 second pair of maxillae (PL I., Fig. 3, mx' ; Fig. 12) forms 

 the floor of the mouth and consists of two pieces which 

 have become united. Fig. 12, gu is the gula, iibt submen- 

 tum, bt mentum, /^ ligula, and x" the three-jointed palpus. 

 For a detailed description of the mouth parts, see Com- 

 stock. Introduction to Entomology, iSSS, pp. 12-16. 



The palpi of insects have been regarded by the 

 majority of entomologists as organs of touch, though 

 some have maintained that they were organs of taste 

 and others of smell. The recent experiments of 

 Plateau^ tend to overthrow these views completely 

 and to demonstrate that the palpi of the Orthoptera 

 and Coleoptera do not possess either one of these 

 three senses. The experiments were made upon fifty 

 individuals, species of Carabus, Dytiscus, Staphylinus, 

 Blatta, Acridium, and other genera. These experiments 

 led to the following conclusions. First, that in the 

 act of eating, the tw^o pairs of palpi remained inactive, 

 For example, meat was placed before a beetle (Cara- 

 bus) ; the insect ate it ; but the palpi during the time 

 were directed backward on each side of the head and 

 not used. 



Second, the suppression of both pairs did not pre- 

 vent the mandibulate insects from eating in a normal 



1 " Palpes des Insectes Broyeurs," Bulletin de la Societe 

 Zoologique de France, t. X., 1885. 



