460 APPENDIX III 



cage can be made by combining a large lamp-chimney 

 with a small flower-pot. 



" The root-cage. For the study of insects that infest 

 the roots of plants, the writer has devised a special form 

 of breeding-cage known as the root-cage. In its simplest 

 form this cage consists of a frame holding two plates of 

 glass in a vertical position 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 them- 

 selves. Immediately 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. 



"Aquaria. For the breeding of aquatic insects aquaria 

 are needed. As the ordinary rectangular aquaria are 

 expensive and are liable to leak v/e use glass vessels 

 instead. 



" Small aquaria can be made of jelly-tumblers, glass 

 finger-bowls, and glass fruit-cans, and larger aquaria can 

 be obtained of dealers. A good substitute for these is 

 what is known as a battery -jar (fig. 168). There are 

 several sizes of these, which can be obtained of most 

 dealers in scientific apparatus. 



"To prepare an aquarium, place in the jar a layer of 

 sand ; plant some water-plants in this sand, cover the sand 

 with a layer of gravel or small stones, and then add the 

 required amount of water carefully, so as not to disturb 

 the plants or to roil the water unduly. The growing 

 plants will keep the water in good condition for aquatic 

 animal life, and render changing of the water unnecessary, 



