The olfactory pits of the Tipulidæ seem to have a somewhat different structure, since the external passage is closed. It is circular, surrounded with a slight chitinous wall, and not covered with bristles. Such pits in their external appearance are like those of the locust (Caloptenus) and many Hymenoptera. They are situated usually on the third antennal joint. _Pachyrhina pratensis_ L. has about 60 of them, as have _Tipula oleracea_ L. and Ctenophora. 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. [Illustration: 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. ] [Illustration: 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. [Illustration: FIG. 275.—Olfactory pits of the antenna of _Melolontha vulgaris_.—After Kraepelin. ] [Illustration: FIG. 276.—Antennal pit of _Melolontha vulgaris_, seen in vertical section.—After Hauser. ]