In a similar way acted the species of Sarcophaga, Calliphora, and Cynomyia. Hauser, in experimenting with these, placed a dish with a large piece of decayed flesh on his writing-table. In a short time specimens of the flies referred to entered through the open window of the room. The oftener he drove them away from the meat would they swarm thickly upon it. Then closing the window and catching all the flies, he deprived them of their antennæ and again set them free. They flew about the room, but none settled upon the flesh nor tried to approach it. Where a fly had alighted on a curtain or other object, the decayed flesh was placed under it so that the full force of the effluvium should pass over it, but even then no fly would settle upon it. =Experiments testing the influence of the antennæ of the males in seeking the females.=—For this purpose Hauser chose those kinds in which the male antennæ differ in secondary sexual characters from those of the female, and in which it is known that they readily couple in confinement, as _Saturnia pavonia_, _Ocneria dispar_, and _Melolontha vulgaris_. The two first-named insects did not couple after the extirpation of their antennæ. Of _Melolontha vulgaris_ twenty pairs were placed in a moderately sized box. On the next morning twelve pairs of them were found coupling. Hauser then, after removing the first lot, placed a new set of thirty pairs in the same box, cut off all the antennæ of the males and those of a number of females. On the following morning only four pairs were found coupling, and at the end of three days five others were observed sexually united. From these experiments Hauser inferred that those insects deprived of their antennæ were placed in the most favorable situation, such as they would not find in freedom; for the space in which the insects moved about was so limited that the males and females must of necessity meet. But at the same time the results of the experiments cannot absolutely be regarded as proving that the males, after the loss of their antennæ, were then not in condition to find the females, because in the case of the above-mentioned moths, under similar conditions, after the extirpation of the antennæ no sexual union took place. If, however, the experiments made do not all lead to the results desired, Hauser thinks that the results agree with those of his histological researches, that in the greater number of insects the sense of smell has its seat in the antennæ. His results also agree with those of Perris. =Structure of the organs of smell in insects.=—The olfactory organs consist, in insects,—_i.e._, all Orthoptera, Termitidæ, Psocidæ, Diptera, and Hymenoptera, also in most Lepidoptera, Neuroptera, and Coleoptera,— 1. Of a thick nerve arising from the brain, which passes into the antennæ.