100 



ENTOMOLOGY 



FIG. 132. 



Section through antennal olfactory 

 pit of fly, Tabanus. c t cuticula; p, 

 pit with peg; pb, protecting bristles; 

 s, sensory cell. After HAUSER. 



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 de- 

 cayed meat, to which they 

 had previously swarmed with 

 great persistence, though 

 their actions in all other re- 

 spects remained normal. 

 Males of many moths and a 

 few beetles are unable to find 



the females (see beyond) when the for- 

 mer are deprived of the use of their 



antennae. 



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 hy- 



podermal in origin and consist, generally 



speaking, of a multinucleate cell (Fig. 



131) penetrated by a nerve and prolonged 



into a chitinous bristle or peg, which is 



more or less enclosed in a pit, as in Ta- 



banus (Fig. 132). In many instances, 



however, the end-organs take the form of 



teeth or cones projecting from the gen- Longitudinal section 



eral surface of the antenna, as in Vespa f antennal lfactory 



' I 33)- These cones are usually less 



organ of wasp, Vespa. 

 c, olfactory cell; en, ol- 



numerous than the pits ; in Vespa crabro, Jj ^dermis ceii^ 



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 



n, nerve; r, rod. After 

 HAUSER. 



