644 
Collecting and Rearing Insects 
and only a short distance apart. The space between the plates of glass, 
is filled with soil in which seeds are planted or small plants set. The width 
of the space between the plates of glass depends on the width of two strips 
of wood placed between them, one at each end, and should be only wide 
enough to allow the insects under observation to move freely through the 
soil. If it is too wide, the insects will be able to conceal themselves. Im¬ 
mediately outside of each glass there is a piece of blackened zinc which slips 
into grooves in the ends of the cage, and which can be easily removed when 
it is desired to observe the insects in the soil.” 
Many caterpillars and other larvae which live above ground in the larval 
stage when ready to pupate crawl down to the ground and burrow into it. 
For these soil must be provided in the rearing-cages, or the larvae when 
ready to pupate must be removed from the meat-safe and bell-jar cages 
to boxes containing soil. This soil must not be allowed to dry out entirely, 
nor yet must it be too moist. Experience is the only teacher that will deter¬ 
mine for the novice the “just right” condition. 
It may be necessary to keep pupae, in cocoons or in underground cells, over 
winter, for many insects, especially in the eastern and northern states, pass 
the winter in the pupal stage. “ Hibernating pupae may be left in the breed¬ 
ing-cages or removed and packed in moss in small boxes. Great care should 
be taken to keep moist the soil in the breeding-cages, or the moss if that 
be used. The cages or boxes containing the pupae should be stored in a 
cool cellar, or in an unheated room, or in a large box placed out of doors 
where the sun cannot strike it. Low temperature is not so much to be feared 
as great and frequent changes of temperature. Hibernating pupae can 
be kept in a warm room if care be taken to keep them moist, but under such 
treatment the mature insects are apt to emerge in midwinter.” Eggs of 
insects, laid in the fall, may also be kept over winter, but one must be careful 
to preserve them in a cold place—as an unheated attic or cellar. 
Directions for making and maintaining observation beehives and 
formicaries (artificial ant’s nests) are given on pp. 532 et seq. and pp. 548 
et seq. of this book. 
Aquarium. —Many accounts of how to make and keep up aquaria have 
been published. The following directions have been written by Miss Isabel 
McCracken, an assistant in my laboratory, who has made and successfully 
maintained many small aquaria in schools: 
To make the aquarium get a board 17X13X1J inches thick, grooved all 
around about 1 inch from the edge with a half-inch groove, and painted 
white. This is for the base. Get two pieces of double-thick glass 15X9 
inches for sides and two pieces 11X9 inches for ends. Set the glass into 
the grooves of the wooden base, bind the corners where the edges of the 
glass come together with strips of coarse muslin or cambric glued on the 
