62 NEW YORK STATE MUSEUM 



through the epidermis of the leaf. The three to five larvae in an 

 egg mass enter through the same orifice, excavate the interior 

 of the leaf for from two to four days, desert the mine and 

 wander to other leaves, often to a considerable distance, where 

 each larva excavates a retreat of its own. The number of larval 

 migrations under natural conditions has not been ascertained. 

 Larval existence is never less than two weeks and probably 

 averages about three weeks. Transformation to the pupa occurs 

 within the mine, the duration of this stage being from six and 

 one-half to ten days. There appears to be but one generation 

 in the northern states, while in the latitude of Washington there 

 may be two generations. The above outline of the life history 

 is an abstract from a more detailed account by Chittenden. 



Natural enemies. This insect is subject to attack in its 

 southern range at least, by the wheel bug, P r i o n i d u s or 

 Aril us cristatus Linn. This large, predaceous bug preys 

 upon the larvae while still within the mine. T r i c h o g r a m m a 

 odontotae How. is recorded as a common egg parasite, while 

 Derostenus primus How. has also been reared from 

 the eggs and is probably a secondary parasite. Two para- 

 sites of the larvae have been recorded, namely, Sympiezus 

 u r o 1 a t a e How. and Spilochalcis odontatae How. 



Control measures. These must obviously be restricted to the 

 more valuable shade trees on lawns and roadsides and, as a 

 rule, are unnecessary in New York State. Thorough and timely 

 spraying with an arsenate of lead, using about two pounds (15 

 per cent arsenic oxid) to fifty gallons of water ought to be 

 effective in protecting the foliage. The application should be 

 made at about the time the leaves are full grown and in New 

 York State the advisability of the treatment must be determined 

 largely by the abundance of the insects. Numerous beetles and 

 slight injury to many leaces in June are liable to result in severe 

 damage during July and early August, unless repressive measures 

 are adopted. 



Jarring the beetles into inverted umbrellas or other mechanical 

 collectors has been suggested for a few trees in yards or lawns. 

 This would be especially applicable to the small trees which, 

 by the way, are the most liable to injury. This treatment would 

 have to be repeated every few days so long as the insects con- 

 tinued abundant. 



