1897.] Entomology. 549 
weeks later the eggs hatch into young, which crawl upon leaves and 
buds. Some of those on the buds survive until the following May to 
lay eggs for the summer brood which develop in the galls. No males 
were found during the two years study. Concerning the formation of 
the galls the author writes: “That this insect by its own operations is 
able to cause a young twig to develop into such an abnormal form is 
very interesting. Physiological botany teaches that all such growths 
as galls caused by insects, and callouses which grow over wounds 
inflicted on trees, are the result of what is known as stimulation. The 
stimulation or irritation in this case is the puncture of the setz of the 
hibernating female into the bud, as previously described. Botanists 
agree that stimulation of this nature sets up a division of the plant cells. 
Each cell divides in the middle, producing two, which after reaching 
full size divide as did the parent cell, thus producing four. As this 
goes on, a swelling is naturally produced, and this swelling is the gall. 
It is not necessary that the insect should sting or poison the plant ; the 
piercing of the setz is sufficient cause for the formation of the gall. 
Essentially the same thing occurs when a limb of a tree is sawed off. 
The inner bark, the growing part of the tree, is injured or stimulated, 
and the cell division begins, causing a swelling or callous, which grad- 
ually grows over the end of the limb. Why the gall should take on 
its characteristic form and color has not been explained. 
“As a result of thestimulation, there may be in addition to the cell 
divisions a deposition of material in the cells, as starch, proteids, resin, 
etc., which appear as minute granules of definite character. The plant 
cells of the gall produced by the insect are abnormally large, with thin 
walls, and contain more starch than those of the unaffected parts of the 
same stem. It may be that this starch is the food on which the young 
lice subsist.”—C. M. W. 
Hemiptera.—Mr. Elmer D. Ball finds’ that all the forms of the 
genus Clastoptera hitherto described from North America with the pos- 
sible exception of C. brevis (Walk.), may be referred to four species, 
viz., C. delicata Uhl., O. proteus Fitch, C. xanthocephala Germ., and 
C. obtusa Say. The species are well figured and described. 
Willis Grant Johnson, A. M., has described’ and figured five new 
species of scale insects belonging to the genera Aspidiotus and Chio- 
naspis, with notes on their habits and parasites. 
Dr. Philip R. Uhler has published‘ a summary of the collection of 
? Proc. of the Iowa Acad. of Nat. Sci., 1895, ITI, 182-194. 
* Bull. Ill. State Lab. of Nat. History, IV, 380-395. 
* Proc. U. S. Nat. Museum, XIX, 255-297. 
38 
