Collecting and Rearing Insects 665 



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 17X13X1^ inches thick, grooved all 

 around about i 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 



