leaves must be changed every day, there is not so much trouble. An important thing to remember with larvae in jars is to thoroughly wash out the jars with cold water every day. If, however, a caterpillar has spun a web on the side and is hung up to moult, it must not be disturbed. In changing the food it is better not to remove the caterpillars from the old food, but having placed a new supply in the jar, cut off the piece of leaf upon which they are and drop it into the jar. If they are not near the moult a little puff of breath will generally dislodge them. Some caterpillars, as _Papilio turnus_, which spins a platform to which it retires after feeding, can best be fed upon a living tree out of doors, but must be covered with a gauze bag to keep off enemies. A piece of paper should be kept _attached_ to each breeding jar or cage, upon which regular notes must be taken _at the time_, giving the dates of every noticeable feature, particularly the dates of the moults and the changes which take place in the form and color at that time." The necessity of outdoor work is further felt in the determination of the facts in the life-history of some insects which have an alternation of generations, as some Gall-flies (_Cynipidae_), and most Aphides. To successfully study these insects constant outdoor observation is necessary, or the species must be inclosed in screens of wire or netting outdoors on their food-plant. Many insects which breed on the ground or on low herbage may be very successfully watched and controlled by covering the soil containing them or the plant on which they feed with a wire screen or netting. The use of wire screens is also advisable in the case of wintering pupae or larvae out of doors. Many species can be more easily carried through the winter by placing them outdoors under such screens during the winter, which insures their being subjected to the natural conditions of climate, and then transferring them to the breeding cage again early in the spring. This is advisable in the case of Microlarvae and pupae. Species which bore in the stems of plants may be easily cared for and leaf-mining and leaf-webbing forms can be secured under screens or covers out of doors for the winter in sheltered situations. Many species which, if kept in a warm room can not be reared, will, if subjected to freezing weather under slight protection in the open air, emerge successfully the following spring.