394 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



about the remarkable increase of the latter species during the past 

 few years is difficult to conjecture, but there can be no question of the 

 effective manner in which they have supplemented each other's 

 work and reduced the numbers of Heterocampa to a minimum. This 

 same principle, namely, the sequence of natural enemies working 

 together in harmony on different stages of the host is what is hoped 

 may be the final result of the introduction of parasites and natural 

 enemies of the gypsy and brown-tail moths which is now being at- 

 tempted in Massachusetts. 



FUMIGATION BOX MATERIALS 



By W. E. Hinds, Entomologist to Alabama Experiment Station 



In connection with investigations relating to fumigation, the 

 writer, assisted by Mr. W, F. Turner, has had occasion to test a variety 

 of materials such as are commonly used in fumigation boxes or tents, 

 to determine their comparative resistance to the transmission of air. 

 The economic entomologist is frequently called upon to recommend 

 materials and types of construction for fumigation outfits. This 

 paper is offered in the hope that the experiments reported may be 

 valuable for their suggestions in this direction. Naturally the material 

 with which fumigation treatment is to be made is one of the first factors 

 to be considered. 



Our work thus far has been principally with carbon di-sulfid and 

 with this substance, the problem of constructing a gas-tight container 

 is complicated especially by its chemical properties. One volume of 

 carbon di-sulfid liquid is supposed to produce 375 volumes of vapor. 

 Naturally therefore, in a closed container, the pressure of gas from the 

 evaporating liquid is a considerable factor. In an experiment to 

 determine the amount of this pressure, a two-necked Wolff bottle 

 was used as the container. In one opening a mercury manometer 

 was tightly fitted through a rubber stopper. Through the other neck, 

 a small quantity of liquid carbon di-sulfid was introduced and the 

 opening then closed tightly with a rubber stopper coated with glycer- 

 ine. In this tight apparatus, the pressure produced by the evaporation 

 of the liquid at a room temperature of 60 degrees F., amounted in a 

 few minutes to more than 2.5 pounds per square inch, or more than 

 .15 of an atmosphere. At higher temperatures, the pressure would 

 be very much greater than this. In all ordinary fumigation chambers, 

 the leakage has been found to be so great that the evaporation of 

 liquid carbon di-sulfid produces no increase of pressure even with a 



