The hardy pupae of most Noctuids and Bombycids, as well as those of many Rophalocera, may be handled with little danger, but other species, if handled at all, or if the cocoons which they make for themselves are broken, can seldom be reared. Constant precautions also must be exercised in the care of the soil and the breeding cages. One of the great drawbacks is the presence of mites and thread worms (Entozoons), etc., which affect dying or dead pupae and larvae in the soil. They also affect living specimens and are capable of doing very considerable damage. To free the soil of them it is necessary at times to allow the earth to become dry enough to be sifted, and then after removing the pupae submit it to heat sufficient to destroy any undesired life there may be in it. _The Insectary._--Up to the present time the work of rearing insects has been largely confined to the breeding cage and breeding jar, already described, which have been kept in the rooms of the investigator. The advantages of having a special building for this purpose are at once apparent and need not be insisted upon. One of the best establishments of this kind is that of the Cornell University Experiment Station, which was fully described in Bulletin No. 3, of that station, November, 1888. The Kansas Experiment Station has a similar building, and one has recently been built for the use of the Entomological Division of the United States Department of Agriculture. The insect-breeding house, or insectary, should comprise a building having workrooms, or laboratories, for microscopic and general work in the study and preparation of specimens, and also a conservatory for the rearing of specimens and the growth of plants, and, where applied entomology is concerned, special rooms for the preparation and the test of insecticides. The building proper should also have a basement storage room for hibernating insects. The laboratory should be fitted with all the apparatus used in the study of insects, including microscopes and accessories and a dark-room for photographic purposes. DIRECTIONS FOR TRANSMITTING INSECTS.