1909.] PUBLIC DOCUMENT — No. 31. 61 



can be done as long as i^resent conditions remain unchanged. 

 Bulletin JSTo. 126 contains the conclusions drawn from this 

 work thus far. 



Studies on the distribution of insect jDests in Massachusetts, 

 and of the factors determining this, have been continued since 

 the last report, but the pressure of other work has prevented 

 much progress in this line. It has become evident, however, that 

 in southeastern Massachusetts the climatic conditions are such 

 that many animals and plants can survive the winters there 

 when this would not be possible in most, probably any, other 

 parts of the State. Study of the lines of dispersal of insect 

 pests shows many southern forms spreading to the north and 

 east from their earlier homes, together with a probably gradu- 

 ally increasing jDower of resistance to low temperatures. This 

 indicates that some, at least, of these insects may be able to 

 live in the southeastern portion of this State if they once reach 

 so far. The reverse condition also holds for northern forms, 

 some of which can undoubtedly live and become injurious in 

 the colder parts of the State. To determine the limits of the 

 possible distribution of these pests is important, as this knowl- 

 edge will be of much practical utility. It is hoped that more 

 time can be devoted to this subject in the future. 



Spraying has been from its very beginning an empirical sub- 

 ject. Many thousands of experiments have been made and the 

 results compared, to learn the causes of success and failure. 

 In spite of this little real progress has resulted in the determina- 

 tion of the fundamental principles, or what might perhaps be 

 termed the science of spraying. Thus far the work has been 

 done wholly with commercial materials varying in composition, 

 both qualitatively and quantitatively, and in most cases with 

 no knowledge of the nature of the variations. The only new 

 line of research taken up by this division during the past year 

 has been on this subject. The plan is to obtain the various 

 stomach poisons in as nearly an absolutely pure condition as 

 possible; to determine their exact composition, qualitatively 

 and quantitatively, and then to test them on foliage of different 

 kinds, under varying conditions of heat, light, temperature, 

 humidity and wind, and to study the results in the hope that 

 by working with materials of unusual purity and known com- 



