Insects the larvae of which live in wood are particularly subject to verdigris, as the Cerambycidae and Elateridae in Coleoptera, the Uroceridae in Hymenoptera and Sesiidae in Lepidoptera. In Hymenoptera the families Formicidae, Mutillidae, and the endophytous Tenthredinidae verdigris very rapidly, and most Diptera also. With all these insects japanned or silvered pins should be used, or when not too large the insects should be mounted on triangles. This verdigrising is associated with what is known as greasing, and this, as just indicated, is also associated with endophytous larval life. The verdigris may be prevented by the methods indicated, and I would strongly advise, as a good general rule to be followed, the rejection of the ordinary pins for all species which, in the larva state, are internal feeders. But there is no way of preventing greasing or decomposition of the fats of the body, which may affect a specimen years after it has been in the cabinet. If the specimen is valuable the grease may be absorbed by immersion in ether or benzine, or by a longer treatment with powdered pipe-clay or plaster of Paris. Insects collected on seabeaches, and saturated with salt water, also corrode the common steel pin very quickly and should be mounted on japanned pins. It is also advisable to rinse such specimens thoroughly in fresh water before mounting. The conviction has been forcing itself on my mind for some time that the naphthaline cones tend to promote greasing and verdigris, and carbolic acid in some small vessel secured to the cork, were, perhaps, preferable. THE REARING OF INSECTS. _General Directions._--The importance, even to the mere collector, of rearing insects to obtain specimens for the cabinet has been referred to from time to time in these pages. The philosophic study of entomology, however, requires much more than the mere collecting of specimens, and one of the most profitable and, at the same time, most fascinating phases of the study relates to the life-history and habits. In no branch of natural history are biologic studies more easily carried on, or the biologic facts more remarkable or interesting. The systematist by such study will be saved from the narrow and hair-splitting tendencies which study of slight difference of characters tends to, while to the economic entomologist it is most essential. In the rearing of insects success will be attained in proportion to the extent to which the conditions of nature in the matters of temperature, moisture, food-supply, and conditions for pupation, are observed.