302 TRANSACTIONS OF THE 



Tarring the trees in October and the beginning of November, 

 and again in March, if faithfully done, and repeated as often as 

 necessary, will be found a good remedy. Circular troughs sur- 

 rounding the trunks of trees and secured as described in my 

 Treatise, and kept filled with cheap oil, have proved to be elfec- 

 tual in preventing the ascent of the insects when crawling up the 

 trees. 



During high winds many of the canker worms are shaken down, 

 and will immediately crawl towards the trees and ascend the 

 trunks. If during the time when they are eating, the leaves of 

 the trees ai'e occasionally tarred, or if the troughs are kept filled 

 with oil, or- with diluted gas tar, many of the Avoi-ms will be 

 caught and thereby destroyed. This has been the case here within 

 the past ten days, during which thousands of the worms have 

 been seen caught in the tar and unable to extricate themselves. 

 By jarring and shaking the trees many of the worms will be dis- 

 lodged, and if they hang suspended, their threads can be broken 

 with a long stick, and then they will fall and loose their clew to 

 the limbs, and will have to get up again by the trunks, in which 

 case the tar and oil will effectually arrest their progress. 



These insects have done a great amount of damage in the 

 vicinity of Eoston during the present month; and though their 

 numbers have lessened very much witliin the past three days, 

 many still remain on the trees. The time of their entire depart- 

 ure is, however, at hand. Eirds and toads have been feasting 

 upon them, and have done their share in lessening their numbers. 

 The ichneumon flies, peculiar to these vermin, are very abundant 

 this year, and will render important service in preventing their 

 increase. Yours truly, 



Thaddeus William Harris. 



Dr. Gardner then proceeded to review this letter : He said that 

 these worms differ from the " canker worm," in the lact — accord- 

 ing to his observation — that they do not descend into the ground 

 to change into the chrysalis, but undergo this change in a rude 

 cocoon which they form on the end of the branch; that they then 

 come forth — both sexes winged — and unite in the branches and 

 lay their eggs. That there is evidently, therefore, only a waste 

 of time and money in tarring trees for this species of worm — ex- 

 cept to catch the fiew dislodged by the wind. He requested in- 

 formation for some effectual substitute. He recommended a 

 light kept burning, into which these millers would fly and be con- 

 sumed. 



