EXPERIMEXT STATION REPORT. 559 



upon it that, there was scarcely room for another. So conspicuous are 

 they that they are readily noticed, and their presence is easily deter- 

 minable. The eggs hatch early in August, and the young caterpillars 

 feed only upon the surface of the leaf, causing them to turn brown, as 

 if they had been burned, somewhat like the efEect produced on elms 

 by the work of the larva? of the elm-leaf beetle. The caterpillars also 

 attack the fruits of the apple and pear. While still young they make 

 a regular dwelling, in which they hibernate during the winter. This 

 is constructed at the ends of the twigs, and made by drawing together 

 a few leaves, lining them with silk and surrounding them with a mass 

 of silken tlireads. They are thus rather conspicuous, and so firmly are 

 the tents fastened to the twigs that they can rarely be removed without 

 using considerable force. The young caterpillars cease feeding and 

 retire into these tents late in September, and there they remain during 

 the winter in a sort of half dormant condition. They become active 

 again about the middle of April, or with the opening out of the new 

 foliage, and feed upon the buds — in some cases even before the leaves 

 have actually unfolded. When feeding upon the foliage they devour 

 everything except the midrib, or, in leaves in which the veins are 

 strong, tlii€'y leave the entire skeleton, giving the tree a very curious 

 appearance. When the caterpillars are numerous they devour not 

 only the buds, leaves and blossoms, but even the green fruit, feeding 

 continuously until early June ; then they spin an open cocoon of coarse 

 silk among the leaves, where they have been feeding, and transform to 

 the pupal stage. They remain in this condition about a month, and 

 then the moths emerge to begin again the life cycle which was started 

 with their appearance. There is therefore only a single brood; but 

 caterpillars appear twice, and where the insects are numerous there 

 may be a defoliation of the trees in spring by the hibernated larvae and 

 again in the fall l)v those that hatched after midsummer. 



Irritation Caused by Hair. 



The caterpillars of this brown-tail moth are clothed with hairs that 

 produce a poisoning or '"nettling" effect when applied to the skin. 

 From experiments made under the direction of Dr. Fernald, it seems 

 very certain that there is no real poison involved, but the hair, when 

 examined under the microscope, appears barbed and set with small 

 spurs or processes, which break off very readily. When a few of these 

 hairs are placed on the skin and rubbed lightly the small barbs break. 



