In the Lepidoptera, olfactory pits are much like those of flies. Hauser describes in detail those of Vanessa io. Those of the moths were not examined, but they can be readily and satisfactorily proved to be the site of the olfactory sense.
Fig. 273.—Longitudinal section through the third antennal joint of a fly (Cyrtoneura stabulans), showing the compound pits from above and in section.—After Hauser.
Fig. 274.—Antenna of Adelops, showing the olfactory organs (p) in the five last joints.
Historical researches in respect to the Coleoptera generally gave a very unfavorable result, contrary to Lespès’s views. That author states that in the Carabidæ the pits are found on the four first joints, but Hauser could discover them in none which he examined. Usually only tactile bristles occur, so also in the Cerambycidæ, Curculionidæ, Chrysomelidæ, and Cantharidæ. In a blind silphid beetle (Adelops hirtus) of Mammoth Cave we have found well-marked olfactory organs (Fig. 274). Similar organs occur in the antennæ of the Panorpidæ.
Olfactory pits, however, without doubt occur in Silpha, Necrophorus, 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 Staphylinus they are less like them, being distinguished by their somewhat larger size and their often more oval form. In Philonthus æneus about 100 such small pits occur irregularly on the terminal joints; besides, in this species on each side of the terminal joint is an apparatus which is like the compound pit generally occurring in the Diptera.
Fig. 275.—Olfactory pits of the antenna of Melolontha vulgaris.—After Kraepelin.
