246 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



coloration ; in fact nearly all the various color varieties may be found upon the same 

 tree. The fall generation is, however, on the whole, darker, with browner hairs 

 than the spring generation. 



As soon as the young caterpillars hatch they immediately go to work to spin a 

 small silken web for themselves, which by their united efforts soon grows large 

 enough to be noticed upon the trees. Under this protecting shelter they feed in 

 company, at first devouring only the green upper portions of the leaf and leaving 

 the veins and lower skin unmolested. As they increase in size they enlarge their 

 web by connecting it with the adjoining leaves and twigs ; thus as they grad- 

 ually work downwards their web becomes quite bulky, and, an it is filled with brown 

 and skeletonized leaves and other discolored matter, as well as with their old skins, 

 it becomes quite an unpleasant feature in our public thoroughfares and parks. The 

 caterpillars always feed underneath these webs; but as soon as they approach ma- 

 turity, which requires about one month, they commence to scatter about, searching 

 for suitable places in which to spin their cocoons. If very numerous upon the same 

 tree the food supply gives out, and they are forced by hunger to leave their shelter- 

 ing homes before the usual time. 



When the young caterpillars are forced to leave their webs they do not drop sud- 

 denly to the ground, but suspend themselves by a fine silken thread, by means of 

 which they easily recover the tree. Grown caterpillars, which measure 1. 11 inches 

 in length, do not spin such a thread. Both old and young ones drop themselves to 

 the ground without spinning when disturbed or sorely pressed by hunger. 



Pupa and cocoon. — Favorite recesses selected for pupation are the crevices in bark 

 and similar shelters above ground ; in some cases even the empty cocoons of other 

 moths.* The angles of tree-boxes, the rubbish collected around the base of trees 

 and other like shelters are employed for this purpose, while the second brood prefer 

 to bury themselves just under the surface of the ground, provided that the earth be 

 soft enough for that purpose. The cocoon itself is thin and almost transparent, and 

 is composed of a slight web of silk intermixed with a few hairs, or mixed with sand 

 if made in the soil. 



The i)upa (Fig. 86, d and e) is of a very dark-brown color, smooth and polished, 

 and faintly punctate ; it is characterized by a swelling or bulging about the middle. 

 It is 0.60 inch long and 0,23 inch broad in the middle of its body, or where it bulges 

 a little all round. 



The moth (Fig. 86,/). — The moths vary greatly, both in size and coloration. They 



,9 ^ ^ J 



Fig. 87. — Ryphantria ciinea ; a-j, wings of a series of moths, showing the variations from the pure 

 white form to one profusely dotted with blacls and brown. 



have, in consequence of such variation received many names, such as cunea Drury, 

 textor Harr., punctata Fitch, punctatissima Smith (Fig. 87). But there is no doubt, as 

 proven from frequent breeding of specimens, that all of these names apply to the 



* We have known the substantial cocoon of Cerura tobe used for this purpose. 



