1924 



ENTOMOLOGICAL SOCIETY 



49 



The figures for 1923 show a distinctly smaller probability of the pest being 

 swept westward from the New York state boundary line than is the case in the 

 Connecticut valley and most evidently so in eastern Massachusetts. Further- 

 more, it has taken over twenty years for the gipsy moth to spread from the 

 vicinity of Boston, Mass., to the New York state line, and if the wind is an 

 important factor, as is doubtless the case, we must conclude that the westward 

 spread into New York state will be still slower. 



The records of the United States Weather Bureau for New England and 

 eastern New York stations are the basis for the following: 



The eastern component for Albany for the past nine years, May 16th to 

 June 8th, has ranged from 1.4 to 22.8 per cent., the average being 11.9. Similar 

 figures for Burlington, Vt., show a range from 2.1 to 12.5 per cent., and an average 

 of 6.4 per cent. Records for a six-year period for Northfield, Vt., indicate a 

 range of 5.4 to 11.2 per cent., with an average of 7.4 per cent. 



It is evident from the above that east winds are much less prevalent in 

 western Massachusetts and eastern New York than on the eastern coast of New 

 England and consequently less likely to carry gipsy moth caterpillars westward. 



In view of the recently discovered infestation in northwestern Vermont, our 

 tabulation of the principal wind components from Burlington and Northfield, 

 Vt., stations for the period when wind-spread is likely to occur is of special 

 interest to Canadians and is reproduced below: 



Summary of Percentages and Principal Wind Components 

 7 a.m. to 7 p.m., May 16th to June 8th. 





Burlington, Vt. 



Northfield, Vt. 





North 



South 



East 



West 



North 



South 



East 



West 



1915 



34.1 



24.9 



36.01 



15.7 



29.7 



26.8 



36.2 



23.4 



39.7 



28.2 



61.9 



52.11 



64.1 



57.5 



54.43 



43.9 



60.5 



40.5 



8.3 

 8.2 



5.06 

 2.1 



12.5 

 6.5 

 4.5 

 5.8 

 4.7 



29.4 

 15.5 

 14.65 

 26.3 

 11.0 

 23.6 

 26.6 

 22.6 

 29.5 



27.3 



43.9 

 40.8 

 45.8 

 29.5 

 48.6 



56.' 7 

 45.4 

 53.7 

 36.3 

 56.9 

 36.4 



'5.'i 

 5.8 

 6.0 



11.2 

 8.2 

 8.0 





1916 





1917 





1918 



30 7 



1919 



17 



1920 



1921 



5.1 

 21 6 



1922 



?2 3 



1923 



23 7 







Average percentage 



29.61 



51.46 



6.4 



22.13 



39.3 



47.5 



7.4 



19.9 



The southern component is especially important to Canada. This averages 

 for Burlington 51.46 per cent., the range being from 64.1 per cent, to 28.2 per 

 cent. The average for Northfield is 47.5, the extremes being 56.7 per cent, and 

 36.3 per cent. 



The weather records were supplemented by releasing from the weather 

 stations named above and localities in Bradford, Vt., Deerfield, Easthampton, 

 and Sheffield, Mass., East Granby, Conn., and Copake Falls, N.Y., nearly 7,000 

 hydrogen-inflated toy balloons for the purpose of obtaining records of actual 

 drift. The balloons were liberated at hourly intervals from 7 a.m. to 6 p.m., 

 eastern standard time, additional balloons being released on the quarter hours 

 between 9 and 11 a.m. and 3 to 5 p.m., and on the half hours from 11 a.m. to 

 3 p.m., and at 5.30 p.m., except when temperatures were below 60°F., or during 

 the prevalence of rain. Observers were also instructed to go on to a fifteen- 



