430 FIFTH KEPORT OF THE ENTOMOLOGICAL COMMISSION. 
tion. Now, the cottonwool is placed by botanist* in a genus different from that of 
tlu- willows, and the strangest thing about it is that the willows are not injured to 
the same degree, even where growing in the neighborhood of the injured cotton- 
wood. This is partly due, perhaps, to the fact that the willow does not suffer so much 
from defoliation as doee the < <>ttonwood, though it is possible that aspecial cottonwood 
feeding race of the speeiee has been of late yean developed in those sections where 
the tree is so largely planted. This would be parallel to the well-known case of the 
apple-maggot (Trypeta pomonella), which, though infesting wild haws and crabs in 
-,wfg|f ff, - 7 
"Fig. 158. — Grub of streaked cot ton wood beetle a eggs, 6, one enlarged; c, newly 
hatched larva? ; d d d. larva- of different ages: e, pupa. nat. size; f. one of the 
middle segments of the body of larva seen from above, showing tubercles, en- 
larged. After Riley. 
all parts of the country, has only taken to feeding on and injuring cultivated apples 
in some of the New England States." 
This last conclusion is rendered all the more plausible from the fact that, so far as 
known, the species in the Eastern States is confined to willow and does not attack 
the cottonwood. 
The perfect beetles wiutered in sheltered localities. In the spring, as soon as the 
cottonwoods begin to leaf out, the beetles pair, aud the females begin laying their 
eggs (fig. 158, a, b). These are placed upon the young leaves in dense ma— 
from ten to a hundred eggs. Each egg is elongate-oval, pale yellowish-white in 
color, rather soft, and about 0.5 mm long. The larva* (fig. 158, c, d) soon hatch and 
develop very rapidly. At first they are black in color aud gregarious in habit, skel- 
etonizing the leaf in the immediate vicinity of the egg-shells. With the succeeding 
molts the color becomes lighter and they separate, feeding upon leaves at some dis- 
tance from their place of birth. These larva?, like those of other species of the genus, 
are peculiar for emittiug from the tips of the tuberculous spines, with which they 
are furnished, a milky liquid, of a pungent, but not altogether disagreeable, odor. 
On attaining full growth they transform to pupa 3 upon the leaf, fastening their hind 
legs to the leaf, and partially throwing off the last larval skin. The perfect beetles 
issue soon after. There are at least three annual generations, and probably more, as 
the development of the insect is very rapid. Professor Snow states* that in the 
month of August only fifteen days are occupied from the hatching point to the issu- 
ing of the adult. 
* Observer of Nature, Lawrence, Kaus., November 23, 1876 . 
