94 
reach them with insecticides, even if we have such as would readily kill 
them. Of such a nature is the "Boll" or "Corn worm," the larva of 
ReliotMs armiger, which in tomatoes lives in the fruit, and in corn lives 
in the ear • in both cases safe from any application we can make. We 
have next a series of forms which in their injurious stage live in the 
soil itself and feed upon the roots of our crops. In cases such as I have 
mentioned our battery of poison is of little or no avail, because there is 
no proper opportunity to make use of it. We must adopt other tactics 
and, if possible, use preventive measures. These may be either posi : 
tive, as where we cover a tree trunk with a substance mechanically 
protecting it from injury ; or they may be more indirect, as when we 
change a crop, or plant late, or early, to avoid the period at which 
injury is done. This latter means of prevention is one which, in my 
opinion, is worthy of the closest attention and consideration on the part 
of entomologists. Not the mere planting early or late, but the question 
of so arranging farm practice as to avoid insect injury to the important 
crop. Insects have a life history which in the vast majority of cases is 
practically invariable. There is, usually, a fairly well-marked date of 
appearance, a tolerably defined period of adult life, and a normal period 
of development. The first and most important problem to be solved is 
the exact life history of the injurious species. That done before the mat- 
ter of insecticides is to be considered at all, the question should be : Can 
we avoid trouble or injury by modifying our practice without impairing 
quantity, quality, or price of crop I In many more cases than is usually 
believed a mere change of time will avoid injury. I do not claim any 
originality in this suggestion, and need only instance the fact that by 
a proper attention to the date of sowing, damage from the Hessian fly 
may be avoided. Eotation of crops, if intelligently practiced, will fre- 
quently prevent trouble when insecticides are out of the question. Our 
fellow- member, Mr. Webster, applied this principle in dealing with the 
Diabrotica longicornis, easily controlling what threatened at one time 
to become a very serious pest. Trap crops, planted principally to save 
the more important staple, are often available. For instance a full 
crop of late squashes may be obtained, free from the borer, Melittia 
ceto, if summer squashes are first planted and the Hubbards and Mar- 
rowfats somewhat delayed. The summer squashes will attract the 
vastly greatest percentage of moths to oviposition, and these may be 
removed after getting an early crop, filled with the larvae that would 
otherwise have attacked the later vines. The proposition to use corn 
as a trap crop to prevent injury from the Boll worm to cotton has been 
forcibly urged by Mr. Mally in a recent bulletin from Dr. Biley's office. 
Methods of cultivation are frequently of use — as for instances in 
squashes again, where borers attack the vines near the roots, In fer- 
tile soil the joints maybe covered at intervals and roots will be formed 
at every such joint sufficient to mature the fruit, even if entirely cut off' 
from the original base of supplies. I have mentioned only a few instances 
