74 The American Naturalist. [January, 



The policy of the Museum at large, with regard to the use of its col- 

 lections by students, is a broad and liberal one. Students are welcome 

 in all departments, and every facility is given to systematists of recog- 

 nized standing. 



On the Girdling of Elm Twigs by the Larvae of Orgyia 

 leucostigma, and its Results. 2 — The white-marked tussock-moth 

 Orgyia leucostigma, has, for a long term of years, been exceedingly de- 

 structive to the foliage of the elms, horse-chestnut and fruit trees in 

 Albany. Fruit trees of considerable size have been killed by their 

 defoliation within a few days, toward the maturity of the caterpillar. 

 Large elms and horse-chestnuts have had the foliage entirely consumed, 

 only the ribs and principal veins remaining. 



In the summer of 1883, a new form of attack by this insect was ob- 

 served by me in Albany. About the middle of June of that year, the 

 sidewalks, streets and public parks where the white elm, Ulmus ameri- 

 cana was growing, were seen to be thickly strewn with the tips of elms 

 two to three inches in length, bearing from four to ten fresh leaves, and 

 comprising nearly all of the new growth of the season. On examina- 

 tion, it was found that above the point where the tips had been broken 

 off, the bark had been removed for an extent averaging about T V of an 

 inch, apparently by an insect. 



As the Orgyia larva? were then occurring in abundance on the trees, 

 they were suspected as being the authors of this injury, and the suspi- 

 cion was verified by ascending to a house-top, where the roof was 

 found to be heaped in the corners with the severed tips, and the cater- 

 pillars engaged upon the branches in the girdling. The explanation 

 of the breaking-offwas simple. With the removal of the bark, the 

 decorticated portion— not exceeding, in many instances, in thickness 

 the diameter of a large pin — dried, and becoming brittle, was readily 

 broken by a moderate swaying of the wind. 



The girdling of the twigs in this manner could serve the Orgyia no 

 such purpose as attends the girdling of several other insects, as the 

 Elaphidion primers of oaks and maples, where it enables the insect to 

 attain greater security for its transformations through this method of 

 reaching the ground, or the Oncideres twig-girdler, where the dead 

 wood affords suitable food for the larva. Probably the conditions of 

 grow tli .luring the spring of this year were such as to render the young 

 bark at the point attacked particularly attractive to the lame; but 

 why, after feeding upon it to so limited an extent, it should cease' and 

 resume its feeding on the leaves, can not be explained. In a few in- 

 :iation for the Advancement of Science, at its 

 . 3, 1895. 



