ZOOLOGICAL ABSTRACTS 
MORPHOLOGICAL STUDIES ON THE INJURY TO 
APPLE CAUSED BY CERESA bubalis 
J. C. GOODWIN AND F. A. FENTON 
Histological studies through lesions made in apple wood by 
Ceresa bubalis, the buffalo treehopper, revealed the cause of the 
peculiar rolling out of the wood characteristic of wounds pro- 
duced by this insect. Sections were made through one, two and 
three year old lesions. A layer of corky tissue is formed over 
the wood cells that are cut by the ovipositor and exposed to the 
air. The two layers of corky bark adjacent to each other do not 
unite and this bark formation results in a wedge-shaped section 
of the limb being separated from the remainder. Because of this, 
part of the cambium layer is isolated from the rest, and is pre- 
vented from uniting with the other cambium to heal over the 
wound. The severed part, as well as the other cells, continues 
to grow and the force exerted results in the peculiar rolling of 
the tissue. Older lesions increase in width but there is a cor- 
responding decrease in depth. The mechanical injury is very 
severe and there are evidences that decay sets in due to the wounds. 
While these may eventually heal over the decay has already 
entered the heart wood and ultimately this secondary injury 
may kill the entire limb. 
Iowa State College 
NEST-DIGGING AND EGG-LAYING HABITS OF 
BELL’S TURTLE 
( Chrysemys Marginata Belli Gray) 
FRANK A. STROMSTEN 
During the summer of 1921 some forty or fifty Bell’s turtles 
dug their nests on the side of a small hill just north of the Iowa 
Lakeside Laboratory. This afforded an excellent opportunity 
for the study of the nest-digging and egg-laying habits of this 
