2:0 EXPERIMENTAL FARMS 



7-8 EDWARD VII., A. 1903 



The White Cedar Twic-BCRni?.— For the past two years the White Cedar or 

 American Arbor-vita^ has been seriously disfigured in the Ottawa district by the at- 

 tacks of the caterpilhirs of some minute moths. These have been reared, and, through 

 the kindness of Mr. Aug. Busck, the species have been identified. The injuries of 

 these minute insects have been so severe throughout the Ottawa district, both on 

 cultivated trees and in the woods and swamps, as to give a rusty sickly appearance to 

 all of the Wiiite Cedars in the district, on account of the large number of the tips 

 of the young twigs which have been killed by the minute caterpillars boring inside 

 them in autumn and again in spring after they had revived from their winter torpor. 

 These tiny caterpillars are about one-eighth of an inch long when wintei sets in, very 

 slender, of a general olive green colour, brownish tr)wards anal end. The head is black 

 and shining, the thoracic shield piceous. These caterpillars pass the winter singly 

 inside the mines and revive again the next year in the hot weather at the end of 

 April. They are about one-quarter of an inch long when full grown. The beautiful 

 little m.oths, silvery wliite with brown markings, were found flying in clouds around 

 th? trees during the latter half of June. It had been noticed last year that there were 

 apparently two different kinds of moths at work on the White Cedars. Consequently, 

 last spring a supply of the infested twigs were sent to Mr. Busck, the eminent tineido- 

 logist of the United States National Museum, who kindly examined the material care- 

 fully and sent me much valuable information concerning the species he found. Mr. 

 Busck writes as follows : — 



' June 13th. I hurry to inform you that the moths from the mines on Thuya 

 occidentalis which you sent me last week for determination, are now issuing, and 

 I find that only a small fraction prove to be Becurvaria thujaella, Kearfott. The 

 large majority (20 to 1) belong to what Packard described as Bucculairix thuiella. 

 The species, however, does not belong to Bucculatrix, but to the genus Argyresfhia, 

 Hubner, and should thus be known as Argyresihia thuiella, Packard. 



' This then is the species which is of economic importance in your case, and I am 

 very glad to have become personally acquainted with it.' 



June 18. — ' Please send me some more of the infested twigs of Thuya occidentalis, 

 because this morning I have found a third species of moth which has issued from the 

 material you sent me before. I should like to get more of this, and there are still 

 several points in the life history of all three species which might profitably be studied 

 more carefully. 



' So as not to get matters mixed up, let me recapitulate. First. I have bred in 

 very large numbers a small pearly white moth with brownish obscure markings (costal- 

 dorsal and apical spots), white head and thorax, white brown-ringed antennae. This 

 is a species of Argyresthia and is the same as was described as Bucculatrix thuiella 

 by Packard. This, in spite of the fact, as I was well aware, that Packard described 

 cocoons from which his moths were supposed to have issued, while the present species 

 does not spin a cocoon, but issues directly from the mines (at least, in captivity), as 

 you have rightly observed. 



' Packard may have observed and wrongly connected with his species other small 

 cocoons, for example those of Becurvaria thujaella, which may have been quite nu- 

 merous in his lot and which are rather striking objects, naturally connected with the 

 issuing species, whichever it be. Strangely enough, the genus Argyresthia generally 

 spins just such a cocoon as described, and I have another species on Cypress which has 

 nice normal cocoons; so, in this particular our species is aberrant. My reasons for 

 identifying the species as Packard's Bucculatrix, which I have all along suspected to 

 be an Argyresthia, are shortly that: (1) no Bucculatrix, so far as I know, feeds on 

 tliis group of plants; (2) a large part of the genus Argyresthia is attached to Juni- 

 perus and its allies; (3) Packard's description fits our species well; (4) no other 

 species is known on Thuya, which could possibly be confounded with it; (5) his 

 f^g^Ti-e — however poor — is not that of a Bucculatrix, but fits decidedly the present 

 rpecies. 



