66 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
In 1921 the soil was so dry that the roots were not so thoroughly 
moistened by the corrosive sublimate. That the material actually 
destroyed or drove off the maggots is shown by the plain evidence of 
tunnelling seen on many plants where no maggots could be detected. 
In the second series one, eight day old and two, ten day old maggots 
survived with the corrosive sublimate, while the creosote dust has 
again had a marked effect, though not so pronounced as the corrosive 
sublimate. The small number found on the check is hard to explain. 
The mortality is here much greater than we would have expected and 
greater than was actually obtained in other experiments. 
These experiments do not settle exactly in what way these two materials 
affect the maggots. It has been said that the corrosive sublimate does 
not destroy the eggs, but repels the young maggots after they hatch. 
In all our experiments, however, we have never known eggs to hatch 
after having been properly treated with corrosive sublimate; such eggs 
after a few days invariably shrivelled up. As for the larvae, it is im¬ 
material, from a practical standpoint, whether they are merely driven 
off, killed outright, or their constitutions undermined to such an extent 
that they die a lingering death, as long as we can state definitely that 
maggots up to a certain age are prevented from injuring the plant. We 
would gather from these figures that it is quite safe to treat with cor¬ 
rosive sublimate up to at least 14 days after the eggs have been laid and 
with creosote up to 12 days and that maggots up to 8 days old in the 
case of corrosive sublimate or 7 days old in the case of creosote are de¬ 
stroyed or driven off. 
The efficiency of these treatments is dependent largely upon the 
season. We know, for example, that when the soil is fairly moist the 
corrosive sublimate penetrates better and is much more effective than 
when it is dry. Accordingly, it would be interesting to compare the 
current year’s results with those of 1921, which was a very dry year, 
whereas in 1922 the precipitation was comparatively heavy and the soil 
was continuously moist. 
Unfortunately no figures are available in the case of creosote dust, but 
the results of similar experiments with corrosive sublimate upon maggots 
of known age are shown in the accompanying tables. Two lots of 
maggots were treated, one under both laboratory and field conditions 
and one under field conditions only. 
The following are the results in tabulated form for the first lot. 
