THE BREEDING OF INSECTS. 



333 



siphon, as air can not enter at either end. If the 

 bore of the siphon is considerably larger than the 

 stream of water flowing into the aquarium, the water 

 in the aquarium will be kept at a constant level, 

 which will be that of the outer end of the siphon. 



To prevent the escape of the insects through the 

 siphon, a cylinder of fine wire gauze, closed at each 

 end with a disk of cork, is fitted over the inner end 

 of the siphon (Fig. 293). 



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 



Fig. 295. — A root cage. 



frame holding two plates of glass in a vertical posi- 

 tion and only a short distance apart. The space be- 

 tween the plates of glass is filled with soil in which 



