ANATOMY AND PHYSIOLOGY 



79 



smell is not always confined to the antennae; indeed the maxillary palpi 

 are frequently olfactory, as in Silf>Iia and Hydaticus; also the cerci, as in 

 the cockroach and other Orthoptera. Experiments indicate that an 

 insect perceives some odors by means of the antennae and others by the 

 palpi or other organs. Hauser found that the flies Sarcophaga and Cal- 

 liphora, after the amputation of their antennae, became quite indifferent 

 toward decayed meat, to which they had previously swarmed with great 

 persistence, though their actions in all other respects remained normal. 

 Males of many moths and a few beetles are unable to find the females 

 (see beyond) when the former are deprived of the use of their antennas. 



sc 



P'iG. 130. Taste cup from maxilla of 

 Bombits. sc, sensory cell; n, nerve. After 

 WILL. 



FIG. 131. Section of antennal olfactory 

 organ of grasshopper, Caloptenus. c, cutic- 

 ula; m, membrane; n, nucleus of sensory 

 cell; Hi 1 , nerve; p, pit with olfactory peg; 

 pg, pigment. After HAUSER. 



End-Organs. Structures which are regarded as olfactory end-organs 

 occur commonly on the antennae, often on the maxillary and labial palpi 

 and sometimes on the cerci. These end-organs are hypodermal in origin 

 and consist, generally speaking, of a multinucleate cell (Fig. 131) pene- 

 trated by a nerve and prolonged into a chitinous bristle or peg, which is 

 more or less enclosed in a pit, as in Tabanus (Fig. 132). In many in- 

 stances, however, the end-organs take the form of teeth or cones project- 

 ing from the general surface of the antenna, as in Vespa (Fig. 133). 

 These cones are usually less numerous than the pits; in Vespa crabro, 

 for example, the teeth number 700 and the pits from 13,000 to 14,000 

 on each antenna. The pits are even more numerous in some other in- 

 sects; thus there are as many as 17,000 on each antenna of a blow fly 



