272 



TEXT-BOOK OF ENTOMOLOGY 



and Caloptenus italicus. On one antennal joint of Caloptenus (Fig. 



268) was often counted 50 pits; on the anterior joints the nura- 

 , ber diminishes to about 30. Hauser 



thinks that in all Orthoptera whose 

 antennae are like those of Caloptenus 

 occur similar pits, as he found them 

 in Stenobothrus (Fig. 269) as well as in 

 (Edipoda. Gryllotalpa possesses similar 

 pits, four to six on each antennal 

 joint, making between 300 and 400 

 pits on each antenna. 1 In Mantis 



FIG. 268. Olfactory organ of Caloptenus. 



FIG. 269. Olfactory pits of the antenna of Steno- 

 bothrus. This and Fig. 268 after Hauser. 



LETTERING FOB FIGS. 268, 269, 273, 275, 276, 278-281. a, a, circular thickening of the skin 

 surrounding the opening of the olfactory pit ; ax, thread-like continuation of the nerve-cell ; 

 b, vesicle-like bottom of the olfactory pit. through which the olfactory style passes ; br, bristle in 

 Fig. 283, stout, and protecting the olfactory pit : b, bent bristle or seta ; ch, chitinous integument of 

 the antennae ; d, seen in section ; /, invaginated pit ; Fr>, Forel's flask-shaped organ ; fco, its operiin<. r 

 seen from the surface ; gl, gland-like mass of cells ; J>yc, hypodermic cells ; ?', entrance into the 

 canal belonging to the pit ; m, olfactory membrane : n, ',' /// ",' 'inc. membrane-forming cell ; n, nerve 

 of special sense; nc, nucleus of the sense- or ganglion-cell ; o, opening into the olfactory pit: />, 

 olfactory pit ; ep, compound pits ; pw, wall of the pit ; *, a large seta; sc, sense- or ganglion-cell ; 

 st, olfactory or sense-style, sometimes peg-shaped ; tb, tactile bristle. 



1 In 1870 I observed these sense-pits in the antennae and also in the cercopoda of 

 the cockroach (Periplaneta americana). I counted about 90 pits on each cercus. 

 They are much larger and much more numerous than similar pits in the antennae of 

 the same insect. I compared them to similar pits in the antennae of 

 the carrion-beetles, and argued that they were organs rather of smelling 

 than hearing. (Amer. Nat., iv., Dec. 1870.) Organs of smell in the flies 

 (Chrysopila) and in the palpi, both labial and 

 maxillary, of Perla were described in the 

 same journal (Fig. 270). Compare Vom 

 Rath's account of the organs in the cerco- 

 pods of Acheta (Fig. 271) ; also the singular 



FIG. 270. A, 6, sense-organ on the abdomi- 

 nal appendages of a fly (Chrysopila) ; c. sense- 

 organ on the terminal joint of palpus of Perla. 



Ki<;. '271. Longitudinal section of part of 

 cercus of .\clti-tu ilmn, xt'n-n : eft. cuticula ; /<<//>. 

 hypndennis ; n. nerve; //'. intrgumental hairs, 

 not sensory : //-. ordinary hair ; /< : '. sensory hair ; 

 A 4 , bladder-like hair ; us, sense-cell. After Vom 

 Hath, from Sharp. 



