1921] McColloch: Method for Studying Insects 229 
bug (Toxoptera graminum Rond) and corn leaf aphis (Aphis 
maidis Fitch). 
Certain modifications in the method of handling the plants 
were necessary for these insects. In order to confine them on 
the stalks of the plants, a small cell was formed in one side of 
the cotton stopper (Fig. 1l-c). The cotton fibers served as 
effective barriers in holding the insects in the cell and exact data 
could be obtained on molting and the length of instars, and, in 
the case of the aphids, on the number of young produced. This 
method was also used to study certain phases of activity of 
several parasites of the Hessian fly puparium. The parasites 
were confined in the cells with plants containing flaxseed in 
their natural position and the behavior and methods of oviposi- 
tion of the parasites were easily observed. In a similar manner 
a study was made of the chinch bug egg parasite (Eumicrosoma 
benefica Gahan). Good results were obtained in confining leaf- 
feeding insects on the leaves by inverting another bottle over 
the plant or by lowering the plant so as to bring a part of the 
leaf into the cell. 
In conclusion, a brief summary is given of the more impor- 
tant advantages of this method of growing plants for life 
history studies. 
1. By certain modifications this method may be enlarged to 
facilitate more extended observations on a much larger number 
of insects. 
2. The manipulation of plants in a water culture has proved 
very satisfactory in growing most of the staple crops, it being 
easily done and facilitates handling the plants in making close 
observations. 
3. This method is especially valuable where the work is 
done under constant conditions, since it eliminates the factor 
of variation in plant food. 
4. The use of the water culture enables one to study many 
phenomena in the insect’s life history that normally are difficult 
to observe and which often necessitate the destruction of the 
plant. 
5. When plants are grown by this method, they may be 
removed and examined under the microscope or binocular 
without injury to the plant. 
