DISPERSION OF GIPSY-MOTH LAEV^ BY THE WIND. 



19 



FEEDING OF LARVAE PRIOR TO DISPERSION BY THE WIND. 



Several of the first-stage caterpillars of various sizes caught on the 

 screens during 1913 and 1914 were selected and examined for the 

 presence of plant cells in the alimentary tract. As all caterpillars 

 blown any reasonable distance by the wind are newly hatched, first- 

 stage specimens, it is impossible to ascertain from a superficial ex- 

 amination which have taken food and which have not. Before the 

 examinations were made it was necessary to fix the material, stain 

 with eosin and methylene blue, section with a microtome, and mount 

 on slides, and this work was performed at Bussey Institute, Harvard 

 University, under the direction of Dr. R. W. Glaser of the Bureau of 

 Entomology. 



Caterpillars were selected during the two seasons which had been 

 borne by the wind a distance of 1, 2, and 6 or more miles, respec- 

 tively, from the nearest source of infestation. Results were as 

 follows : 



Table VII. — Percentages of small caterpillars having fed which were caught on screens 



during 1913 and 1914. 



Year. 



Locality and distance carried by wind. 



Number of 



caterpillars 



that had 



fed. 



Number of 



caterpillars 



that had 



not fed. 



1913 





13 

 1 



2 



7 

 



7 



1914 



Isles of Shoals, N. H. Infestation in brushland around screen 





 5 





Isles of Shoals, N. H.; 6 miles or more from infestation on the main- 



8 





Merrimac, Mass.; J to 1 mile from heavy infestation in all directions. . 

 Total 



2 





23 22 











Of the 45 small caterpillars prepared and examined during the two 

 years that experiments were conducted, 23, or 51 per cent, had con- 

 sumed a very small amount of food, while the remainder, 40 per 

 cent, showed no signs of it. 



COMPARISON OF WEATHER DATA BETWEEN PROVIDENCE, R. I., AND 

 AMHERST, MASS., WITH REFERENCE TO DISPERSION IN 1913. 



The period in which first -stage larvae were borne by the wind in 

 1913 in eastern Massachusetts was from May 9 to June 5, inclusive. 

 After comparing the hourly wind direction from 7 a. m. to 6 p. m. 

 when there was no min and the temperature was 50° F. or above at 

 Providence, R. I., 1 and Amherst, M;iss.,' one notes a slight difference 

 in the total wind movement in (lie various directions. For instance, 

 in Providence the wind blew from the northwest 92 hours, from the 



iei recorda at Providence weri soured from n 

 those :ti Amherst from tbe Experiment Station. 



il the u. 8. Weather Bureau, and 



