A genus of Ichneumons, parasitic upon _Periplaneta_ and _Blatta_. _Ref._--Westwood, Trans. Ent. Soc., Vol. III., p. 237; Ib., Ser. II., Vol. I., p. 213. _Symbius Blattarum_, Sund. INSECTA (_Coleoptera_). The apterous female is parasitic upon _P. americana_ and _B. germanica_. _Ref._--Sundevall, Isis, 1831. * * * * * SENSE OF SMELL IN INSECTS. Since the printing of the sheets which describe the organs of special sense, we have become acquainted with two experimental researches of recent date, instituted for the purpose of determining whether other organs, besides the antennæ, may be specially concerned with the perception of odours by Insects. Prof. Graber (Biol. Centralblatt, Bd. V., 1885) has described extensive and elaborate experiments upon various Insects, tending to the conclusion that the palps and the cerci may be sensitive to odours, and that in special cases the palps may be even more sensitive in this respect than the antennæ. Cockroaches, decapitated, but kept alive for some days, were found to perceive odours by means of their cerci. His general conclusion is that Insects have no special sense of smell, but that various parts of the surface of the body are furnished with nerve-endings capable of perceiving strong odours. Prof. Graber’s results are known to us only through the abstract given by Prof. Plateau in the paper next to be mentioned. Prof. Plateau (Compt. rend. de la Soc. Entom. de Belgique, 1886) relates experiments upon the powers of scent resident in different organs of the Cockroach. Two Cockroaches had their palps (maxillary and labial) removed; two others had the antennæ removed. An evaporating dish, 8 inches in diameter, was then partly filled with fine sand. In the centre of the dish was set a circular box of card, without bottom, 2 inches in diameter, and 1-4/5 inches high. In this box bread moistened with beer, a bait very attractive to Cockroaches, was placed, and renewed daily. The four Cockroaches were allowed to run about in the dish outside the box, and to feed upon the bread at pleasure by climbing over the enclosure. Observations were made late at night for a month, when it was found that, except on the first night, when the Insects ran all over the dish, none of the Cockroaches without antennæ made their way to the food; while twenty-three times one of the Cockroaches without palps, but with antennæ intact, was found to be feeding; in one instance, both were so found. Plateau observes that a special sense of smell can only be claimed for organs which are able to detect faint and distant odours, and that experiments made with powerful odours close to the body of the Insect may lead to fallacious results. The perception of faint odours cannot be effected by the palps or cerci of the Cockroach, but only by the antennæ. THE END. Printed by McCORQUODALE & CO, Limited, Leeds.