“The base consists of a round plate of strong zinc, with two vertical rims, an inch high, placed one within the other, an inch apart, and soldered to the basal plate so that the outer one is water-tight. The inner rim must be perforated with small holes as close to the bottom as possible. The space inside the inner rim must be filled with fine sand, on which the pupæ should be laid. The space between the two rims is then filled with water, which, finding its way through the holes in the inner rim to the sand, causes the necessary moisture. Over the whole is put a bell-shaped cover of wire gauze, which must fit tightly over the outer rim. In this receptacle the pupæ remain untouched, and receive fresh moisture, as above indicated, if required by the drying of the sand.”
The hardy pupæ 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 (Entozoöns), etc., which affect dying or dead pupæ and larvæ 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 pupæ 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.
It is very desirable in transmitting insects from the field of exploration, or from one entomologist to another, for information, exchange, or other purpose, that they be properly secured and packed. Pinned and mounted specimens should be firmly fixed in a cigar box, or a special box for mailing, and this should be carefully but not too tightly wrapped with cotton or other loose packing material to a depth of perhaps an inch, and the whole then inclosed in stiff wrapping paper. It is preferable, however, to inclose the box containing the specimens in a larger box, filling the intervening space, not too firmly, with cotton or other packing material. Where specimens are to be sent to a considerable distance it is advisable also to line the box in which they are placed with cotton, which serves to catch and hold any specimens which may become loose in transit. In the case of alcoholic specimens each vial should be wrapped separately in cotton and placed in a strong wooden or tin box. Special mailing boxes for alcoholic specimens have been devised, and a very convenient form is herewith figured. It is an ordinary tube of wood, with a metal screw top, and the interior lined with rough cork. These tubes are made in various sizes to accommodate vials of different dimensions.
Fig. 126.—Wooden-tube mailing-box: a, tube; b, cover (original.)
In mailing living specimens the essential thing is a strong box, preferably tin, made as nearly air-tight as possible. I have found it very convenient on long trips to carry with me a number of tin boxes in the flat ([Fig. 127]), combined in convenient packages, ready to be bent and improvised in the field. For this purpose get any tinsmith to make out of good tin a number of pieces cut of the requisite dimensions both for the bottoms and the covers, carefully cutting the corners to permit the proper bending of the sides. These improvised boxes will prove useful for keeping living larvæ with their food-plants, especially if tied up in stout brown paper to prevent any exit from the unsoldered angles. They will also answer admirably for mailing or otherwise sending specimens to their ultimate destination. In the case of larvæ a quantity of the food-plant should always be inclosed in the box.