OLFACTORY ORGANS OF BEETLES 



275 



(Adelops hirtus) of Mammoth Cave we have found well-marked 

 olfactory organs (Fig. 274). Similar organs occur in the antennae of 

 the Panorpidae. 



Olfactory pits, however, without doubt occur in Silpha, Necro- 

 phorus, Staphylinus, Philonthus, and Tenebrio. The openings of the 

 pits are small and surrounded with a small chitinous ring; in Silpha, 

 Necrophorus, and Tenebrio they cannot easily be distinguished from 

 the insertion-cavities of the bristles, but in Philonthus and Staphy- 

 linus they are less like them, being distinguished by their somewhat 

 larger size and their often more oval form. In Philonthus <.i } neus 

 about 100 such small pits occur irregularly on the terminal joints ; 

 besides, in this species on each side of the terminal joint is an 



FIG. 275. Olfactory pits of the antenna of Melolontha vul- FIG. 276. Antennal pit of 



garis. After Kraepelin. Melolontha vulgaris, seen in 



vertical section. After Hauser. 



apparatus which is like the compound pit generally occurring in 

 the Diptera. 



Very remarkable pits occur in the antennal lamellae of Melolontha 

 vulgaris (Fig. 275) and other lamellicorns. On the outer surface of 

 the first and seventh (in the female the sixth) antennal leaf, as also 

 on the edges of the other leaves, only arise scattered bristles ; on 

 the inner surface of the first and seventh leaves, as also on both sur- 

 faces of the second to sixth leaves, are close rows of rather shallow 

 depressions of irregular form, some circular, others regularly hex- 

 agonal. Their number is enormous : in the males 39,000, in the 

 females about 35,000, occur on each antenna. 



The antennal pits and teeth of Dyticus marginalls are morphologi- 

 cally and physiologically identical with those of bees and wasps. In 

 Anophthalmus bilimekii, Hauser found on the last antennal joints 

 about 60 teeth, which essentially differ in form from those previously 



