130 MASS. EXPERIMENT STATION BULLETIN 192. 



The Gypsy Moth (Porthetria dispar L.). 



Early in January, 1917, several batches of the eggs of this insect, col- 

 lected from trees shortly before, were submerged in two or three feet of 

 water in a pond, two lots being left in the basement of the screenhouse as 

 a check on the hatch of the others. The hatch of those kept in the base- 

 ment was nearly perfect, while less than 1 per cent of those taken from 

 the pond May 16, and none of those removed May 24, May 29 or June 

 2, hatched. All these eggs were put on sand in pails when taken from the 

 water, and kept in the upper part of the screenhouse, as were also those 

 from the basement. A lot taken from the pond June 7 was put at once 

 on the station bog, the egg masses being spread under the vines, with 

 care to place them as a moth might lay them. This lot was observed 

 until July 4, and but one egg was known to hatch, a newly hatched worm 

 being found on a vine above the eggs June 21. These results confirm 

 those of former years in showing that the eggs do not endure very late 

 holding of the winter water. 



Mr. C. W. Minott of the Bureau of Entomology and the writer co- 

 operated in an experiment at the Wankinco bog in 1917, to determine the 

 amount of the wind drift of the first-stage caterpillars. A horizontal 

 tanglefoot-covered screen was used. This was placed 583 feet on its 

 south side, 837 feet on its northeast side, and 635 feet on its northwest 

 side from the upland. It covered 53| square feet, and during the wind- 

 drift period caught two of the larvae. If this shows fairly the wind drift 

 onto the central part of the bog, 1,634 gypsy worms per acre blew onto 

 it during the season. This result is significant, as the bog is so large and 

 its environs were so little infested in the early spring that it seemed 

 doubtful if the experiment would pay. 



On June 15, 1917, a grower told the wTiter he had recently successfully 

 treated gypsy caterpillars floating on the flowage of some bogs with 

 kerosene. He used 5 gallons to 6 acres, and poured it on the water on 

 the windward side. The worms must have been fully a third grown. 



On June 9 the writer sprayed oak bushes much infested with gypsy 

 caterpillars with Black-Leaf 40 used at the rate of 1 part to 400 parts of 

 water, with resin fish-oil soap added at the rate of 2 pounds to 50 gallons. 

 The worms were in their second, third and fourth stages, being from 6 to 

 15 millimetres long, and the spray killed all it hit. Other bushes covered 

 Avith gypsy worms were sprayed with Black-Leaf 40 used at the rate of 

 1 part to 800 parts of water, with soap as before. This treatment was 

 partially effective, but very many caterpillars survived it. On June 19 

 infested bushes were sprayed with Black-Leaf 40 used at the rate of 1 

 part to 400, soap being added as before. The caterpillars were in theii- 

 third, fourth and fifth stages, being 10 to 22 millimetres long, and the 

 treatment killed most of them, though many of the larger ones survived. 

 Nearly full-grown caterpillars were sprayed July 5 with Black-Leaf 40 

 used at the rate of 1 part to 200, with soap as before. This was not 

 effective. 



