88 



ENTOMOLOGY 



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 antennae. 



se 



FIG. 132. Taste cup from maxilla of FIG. 133. Section of antennal olfactory 

 Bombus. sc, sensory cell; n, nerve. After organ of grasshopper, Caloptenus. c, cutic- 

 WILL. . ula; m, membrane; n, nucleus of sensory 



cell; nv, 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 hypo- 

 dermal in origin and consist, generally speaking, of a multinucleate 

 cell (Fig. 133) penetrated by a nerve and prolonged into a chitinous 

 bristle or peg, which is more or less enclosed in a pit, as in Tabanus 

 (Fig. 134). In many instances, however, the end-organs take the 

 form of teeth or cones projecting from the general surface of the antenna, 

 as in Vespa (Fig. 135). 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 insects; thus there are as many as 17,000 on 

 each antenna of a blow fly (Hicks). The male of Melolontha vulgaris, 

 which seeks out the female by the sense of smell, has according to 

 Hauser 39,000 pits on each antenna, and the female only 35,000. Pits 

 presumably olfactory in function have been found by Packard on the 

 maxillary and labial palpi of Perla and on the cerci of the cockroach, 

 Periplaneta americana. Vom Rath has described four kinds of sense 



