IOO 



ENTOMOLOGY 



insect perceives some odors by means of the antennae and 



FIG. 132. 



Section through antennal olfactory 

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

 pit with peg; pb, protecting bristles; 

 s, sensory cell. After HAULER. 



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- 

 eral 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 



Longitudinal section 

 of antennal olfactory 

 organ of wasp, Vespa. 

 c, olfactory cell; en, ol- 

 factory cone; ct, cutic- 

 ula; h, hypodermis cells; 

 n, nerve; r, rod. After 

 HAUSER. 



