1924 ENTOMOLOGICAL SOCIETY 31 



The entomologist is also confronted with climatic conditions which in many 

 sections of the country are most variable. Meteorological data is often most 

 difficult to interpret satisfactorily in so far as its effect on insect increase is 

 concerned. 



Few seasons are comparable as to weather conditions, and when information 

 is tabulated covering a decade or more showing the effect of any control measure, 

 be it natural or artificial, which indicates that all the results point in the same 

 direction, there is evidently something wrong, either with the compiler or the 

 compilation. 



It is said that statistics can be used to prove almost anything that is desired, 

 and we as entomologists should exercise great care so that the conclusions that 

 are drawn will be well balanced and will stand the test of time. 



In some sections of North America weather conditions remain rather con- 

 stant for considerable periods, and this simplifies the weather factor. In most 

 sections, however, these conditions are not so stable and more complications 

 result. 



Both temperature and humidity are important, and react on the insect in 

 all its stages. Our knowledge is very limited along these lines, although here 

 and there attention has been given to the behaviour of some of our insect pests 

 from this angle. 



There is great variation in different species in this respect. Our experience 

 in shipping parasites and predaceous insects has been that lack of a reasonable 

 amount of moisture usually causes high mortality. This is particularly notice- 

 able when the insects are not dormant. 



Certain Tachinid puparia do not require moist conditions. They can be 

 shipped without special precautions of this sort, and can be handled successfully 

 with a minimum amount of care. Excessive temperatures often cause high 

 mortality among insects. In the case of the gipsy moth, high temperatures, 

 particularly if accompanied with insufficient or unsatisfactory food, furnish 

 conditions favourable to an outbreak of the wilt disease which frequently sweeps 

 away large numbers of the caterpillars. 



Late frosts shortly after hatching, particularly if accompanied with heavy, 

 beating rains, frequently result in the destruction of many small larvae, due to 

 temporary shortage of food supply or the inability of the small caterpillars to 

 reach food after they have been washed or blown from it. The best records 

 that we have been able to obtain indicate an enormous rate of mortality in the 

 first and second larval stages. When weather conditions are very unfavourable 

 in the spring it is doubtless true that only the most vigorous larvse survive. 

 In the winter, when the temperature drops below 20° F., gipsy moth eggs 

 are killed unless they are protected by snow or ice or have been deposited in 

 concealed situations. This has been demonstrated by the experimental work 

 conducted by Dr. J. N. Summers. 



I have referred to the gipsy moth because of more intimate personal know- 

 ledge of this insect. The same factors are present and affect other insects to a 

 greater or less extent. 



There are other factors which have a bearing on the increase of insect life, 

 but those already mentioned are among the most important. 



From what has already been said it would appear to most persons, except 

 the trained entomologist, that insect life would be sufficiently held in check 

 without help from other sources. This is not the case, however. The novice 

 needs only to make collections of insects that are attracted to strong lights 

 during the summer to be convinced that widespread havoc would result were 



