The Cabbage Root Maggot. 535 



be easily attached to assist ia inserting the instrument if necessary. The 

 reservoir in our instrument (Fig. iS) is 2 feet long, 2^3 inches in diame- 

 ter, and holds 2 quarts of liquid. 



All the parts of the injector are made of brass or tin except 

 the simple discs of leather used in the valves, v. These can be 

 -easily replaced when worn. The price at which it can be made and sold 

 -will depend upon the demand and also on its size and the material 

 •of which the reservoir (r) is made, whether tin or brass. The 

 reservoir in the one shown in operation in figure 18 is 2 feet 

 long, 2^ inches in diameter, and holds about 2 quarts of the 

 liquid. This is about the right size for use against the Cabbage 

 Root Maggot, as one filling of the reservoir will treat about 

 500 plants, using a teaspoonful at each plant. It could easily be 

 made larger without adding much weight to the instrument, for a 

 slight increase in the diameter of the reservoir would greatly in- 

 crease its capacity. Mr. McGowen can make them any size de- 

 sired. The one shown in figure 18 can be made for from $3 to $5, 

 depending on the demand for it and the material used ; in large 

 quantities, they could doubtless be made for less. The brass in- 

 strument we have has a capacity of 2 quarts and weighs when 

 empty ^y^, pounds, and when full of water 4 pounds more. Thus 

 in gardens it will require but little more than the weight of the 

 loaded instrument to force it into the soil. But if a larger instru- 

 ment was needed it might be well to have a foot-rest attached 

 near the bottom. 



In fact, we believe the instrument can be so adapted as to work satisfactorily 

 wherever the liquid is now used against underground insects. For instance, 

 it will facilitate the application of the liquid to the new Grape Root-worm. 

 {Fidia viticida) which has recently appeared in Ohio ; and it is possible, as 

 Prof Cook suggested in 1880, that the Peach Borer {Sannina e.vitiosa) may 

 be killed by the substance, especially on small trees where it works almost 

 entirely on the roots (we shall try some experiments in this line in the 

 spring). Many other instances might be mentioned where it would be prac- 

 ticable to use the liquid, now that we have a suitable instrument to apply it. 

 In fact, this simple and cheap injector should open up a whole field of ex- 

 perimentation with this liquid ; why not use it against the root form of the 

 Black Peach Aphis (discussed in Bulletin 49) or the Wooly Aphis of the 

 apple. 



The liquid is very volatile and will thus quickly evaporate if 



