34 



found two applications of the poison dust (one part of London purple and sixty parts of 

 wood ashes) quite sufficient to keep the plants free from the young grubs. I am inclined, 

 however, to recommend the use of plaster instead of ashes in a wet season. It seems to ad- 

 here better to the leaves when rain falls on them. 



To my surprise there was here no second brood of the beetles this year. A few 

 belated individuals appeared, but nothing that deserved the name of a brood. Of course 

 the earliest potatoes were ripe before the usual second emergence, but the late ones grew 

 and were green almost till frost came, but were perfectly uninjured after the beginning 

 of July. I cannot learn if this is usual, for I can find no one who has been sufficiently 

 observant, or who is sufficiently acquainted with the habits of insects in general, and with 

 those of Doryphora 10-lineata in particular, to tell me. They come, they are here, they 

 go, but when, why and how they come and go is a matter which no one here seems to 

 have considered. Another year I shall try and make more general observations on this 

 point. 



Not only is the potato beetle less mischievous here than it was in Ohio, but all the 

 others named follow suit. The apples are much less infested with worms ; blister beetles 

 I have scarcely noticed ; corn worms are quite innocuous, and as for the cherry weevil, 

 though the crop this year was not heavy for all kinds of cherries, and the fruit should, 

 therefore, be at its worst, I have not seen a score of them all through the summer. I 

 noticed one or two on my own trees showing the crescent cut, but no more. It was 

 almost as safe to eat the fruit unexamined, as it is in England. 



--^L.u By the way, I never hear any apprehension expressed concerning the migration of 

 Conotrachelus nenuphar across the Atlantic. Though fruit is less abundant there than 

 here, yet the introduction of the pest would be a very serious drawback to the enjoy- 

 ment of plums, peaches, and cherries, not to mention the loss caused by its attacks on the 

 apple. 



On the other hand, if these insects are less injurious in Pennsylvania than in Ohio, 

 the imported currant worm is more so, and the growth of currants is greatly limited by 

 its ravages. Yery few persons seem to know what can be done by the use of poison to 

 rescue the bushes and the currants. Great, but totally unfounded prejudice also exists 

 against the use of poison, even on potatoes j many people seeming to fear lest the potato 

 should absorb suAcient arsenic as to render its use as a table vegetable dangerous. It is 

 needless to say that all such ground of alarm has long been set at rest in the minds of 

 those who have followed the progress of economic entomology. But prejudice is blind 

 to reason and slow to die away. 



In addition to this the various web-worms on the forest trees are vastly more numer- 

 ous here than they were at Yellow Springs. In earliest spring and before the leaves are 

 generally out, the American Lackey Moth ( G. Americana ) takes possession of the cherry 

 trees and covers the young foliage with its net. Soon afterwards the Forest Lackey 

 (C. sylvatica ) follows on the same tree, but more frequently on the apple, and later still 

 the walnuts are attacked by the fall web worm ( H. textor ), whose nests remaining on 

 the trees after the fall of the leaf, disfigure them through the winter. 



This year, also, the oak catarpillar f D. Senatoria ) has wrought great ravages in the 

 forest. I have seen hillsides that looked as if fire had passed over them in consequence 

 of the destruction of the foliage by millions of this species. In the woods they could be 

 found crawling over almost every square foot of ground, and lying dead by dozens in 

 every pool of water. The sound of their falling frass, too^ was like a slight shower of 

 rain. Farmers tell me they have never known them so abundant before within their 

 recollection. Harris says this species live on the white and red oaks ( Q. alba and 

 rubra ) in Massachusetts. Here the white oaks were untouched, and the red oak is 

 n«t abundant. The food of the caterpillars was almost exclusively the foliage of the black 

 oak (Q. tinctoria)^ the scarlet oak (Q. coccinea), and the bear or scrub oak f Q. ilici- 

 folia J, 



EXPERIENCE WITH INSECT POWDERS. 



I have used the Pyrethrum powder, Buhach " mixed with ten parts of flour, as 

 the easiest and most effectual remedy for the cabbage worm. It was mixed in 1881 and 



