94 BOARD OF AGRICULTURE. [Pub. Doc. 



grown the caterpillars are one and one-half to two inches in 

 length, with yellowish, longitudinal markings, and clothed 

 with grayish hairs. They wander about on walks and fences 

 in search of places to pupate, and in this latitude often find 

 shelter beneath loose rubbish on the surface of the ground ; 

 otherwise, the cocoons are placed at the base of the tree or 

 on fences near the ground. Pupation takes place in Sep- 

 tember, and the white moths do not emerge until the fol- 

 lowing July. As already pointed out, the web worm is 

 extensively preyed upon by birds. It is also parasitized 

 by various ichneumon flies. In eastern Massachusetts it 

 is often confounded with the brown-tail moth, whose webs, 

 however, are much smaller and more compact, and whose 

 caterpillars feed outside of the web, returning to it for 

 shelter only. 



A common practice among farmers is to burn the webs by 

 means of a torch. If this is done as soon as the insects ap- 

 pear, no strong objection can be raised against the practice, 

 as the large branches will not be injured, as is often the case 

 where tent caterpillar webs are burned in this way. A 

 better practice is to spray thoroughly with arsenate of lead 

 as soon as the first webs are noticed. The poisoned foliage 

 will be drawn into the web, and the caterpillars destroyed. 



And right here we may well emphasize a unique property 

 of arsenate of lead. This insecticide adheres in a notable 

 degree to the foliage, and trees that have been thoroughly 

 and heavily sprayed with it in the spring will be exempt 

 from damage by the web worm in the fall. 



Some years ago the writer sprayed part of a row of pear 

 trees, about May 15, to destroy the brown-tail moth. Va- 

 rious strengths of arsenate of lead were used, and it was 

 found that trees sprayed with this insecticide at the rate of 

 3 or more pounds to 100 gallons of water were completely 

 exempt from damage by the web worm the following Au- 

 gust. Lower proportions of the poison did not give satis- 

 factory results, while the trees in the row that were not 

 sprayed were badly injured by the web worm. As the trees 

 sprayed were in the middle of the row, the result of the 

 treatment was unmistakable. 



