370 REPORT OF THE COMMISSIONERS OF 



From ten to fifteen days are passed in the pupal state. At the end of this period, 

 the wingless female emerges and crawls upon her cocoon, pairing takes place, and 

 immediately afterwards deposition of the eggs begins, as stated by Dr. L. O. Howard. 

 They are laid in masses as described above, the eggs of a cluster ranging in number 

 from iooto 500, as given by several writers. In what appeared to be a good sized 

 mass collected in Albany, there were 330 eggs. After her full complement has been 

 discharged, the female dies and drops to the ground. In Albany there is normally 

 one annual generation, but in New York city and vicinity and in Boston, Mass., there 

 are two broods, while at Washington, D. C, there are three broods each year, according 

 to Dr. Howard. 



The young larvae feed upon the under surface of the foliage (Plate 1, figure 6), and 

 as they increase in size more and more holes are eaten, till, when full grown, all but 

 the main ribs of the leaves, well represented in plate I, are devoured. A peculiar habit, 

 recorded by the late Dr. Lintner but not observed by others outside of Albany, is the 

 girdling of elm twigs by the larvae of this insect. This is caused by their eating a 

 portion of the bark around the twig near the beginning of the season's growth (Plate 

 I, figure 8). The affected tips soon die, break off, and fall in numbers to the ground. 

 The larvae drop from the trees readily, specially when young, suspending themselves 

 by silken threads, and then may be blown or carried considerable distances. When 

 nearly full grown, the caterpillars travel to a great extent ; this is said to be specially 

 true of the larger ones, females, and more likely to occur if they are very abundant. 

 At such times there may be quite a migration to other trees. The cocoons are 

 found very generally on the trunks and particularly on the under side of the larger 

 branches. 



The wingless females, at the time they emerge from their cocoons, attract large 

 numbers of the opposite sex. Dr. Lintner records an instance of one attracting one 

 hundred males within an hour. Collections at electric lights in Poughkeepsie, N. Y., 

 by Dr. Dyar, show that the males fly during July and into August. 



Though this insect is commonly destructive to comparatively few trees, it has been 

 recorded as feeding on a number of others, as the following list will show : Linden, 

 horsechestnut, buckeye, maples (specially the soft and Norway), box elder, honey 

 locust, apricot, garden plum, wild plum, garden cherry, choke cherry, rose, pear, apple, 

 quince, ash, elm (several species), sycamore or buttonwood, butternut, black walnut, 

 hickory, oak, birch, alder, willow, poplar, spruce, fir, larch and cypress. 



This native species "ranges from Jacksonville, Fla., to Nova Scotia on the eastern 

 coast and extends west certainly as far as Keokuk, la., and probably farther," according 

 to Dr. L. O. Howard. It has been recorded as common in Nebraska, and reported as 

 present in Oregon. 



