8 BULLETIN 273, U. S. DEPARTMENT OP AGRICULTURE. 



ing was completed. In 1914 there was an abnormally late spring, 

 which shortened the hatching season, and wind dispersion was noted 

 about one week after the first date and continued about the same 

 period after the last was observed. The total period over which 

 windspread may be expected is from 27 to 30 days in a normal 

 spring, and from 18 to 20 days during a late spring. Ordinarily the 

 maximum dispersion is effected during 10 to 15 days of high tempera- 

 tures and favorable winds. 



LONGEVITY OF FIRST-STAGE LARVAE AFTER BECOMING ENTRAPPED IN 



TANGLEFOOT. 



In connection with the experiments conducted by using tanglefoot 

 on screens to catch caterpillars blown by the wind, it became essential 

 to know about how long they would live after becoming entangled. 

 As a test, tanglefoot was smeared at various depths on heavy paper 

 and 100 caterpillars dropped into these. Examinations were made 

 at intervals from the time the experiment was started, and it was 

 noted that after three hours practically all were living; after six 

 hours only two were attempting to move, and these were in a very 

 thin smear. After eight hours 65 were dead, and 35 showed signs of 

 life when disturbed. The following morning, after 24 hours, all were 

 dead except seven, and these were in very thin smears, which had 

 little effect upon them. 



The length of life depended upon the density of the tanglefoot in 

 which they were placed. If the caterpillars in attempting to free 

 themselves became submerged below the spiracles, which often hap- 

 pened in 3 to 5 hours, they died shortly after. As a result, cater- 

 pillars lodged in globules of tanglefoot on the screens died in 4 to 6 

 hours, while those in very thin spots lived 24 or more. 



SCREEN EXPERIMENTS AT SALISBURY BEACH, MASS., IN 1913. 



April 24, 1913, a large screen (PL III, fig. 1), as described, was 

 erected on the edge of the marsh area near the beach, on a site which 

 was 1 mile distant from infested woodlands to the northwest, 1| 

 miles to the west, and 2 J miles to the southwest. The area to the 

 east, composed of sand dunes, contained small amounts of vegetation, 

 on which gipsy moths could thrive, but this was properly scouted 

 and cleaned for an experiment on reinfestation by the wind. 



The temperature, wind direction, and wind velocity were taken 

 each day at alternate hours from 9 a. m. to 5 p. m., and the screen 

 was examined most days when the winds were fair for windspread 

 from the west. Mr. F. W. Graham was in attendance at this screen 

 and made many of the following observations and notes. 



No larvae were blown on the screen, which was one-fifth mile from 

 the ocean, by winds coming directly from the east. Larvae were 



