The Ohio ^J^Catiiralish 
PUBLISHED BY 
The Biological Club of the Ohio State Uni'versity. 
Volume IV. APRIL, 1904. No. 6. 
TABLE OF CONTENTS 
Cook— G alls and Insects Producing Them 115 
Cook— Galls and Insects Producing Them. Appendix 1 140 
News and Notes 148 
GALLS AND INSECTS PRODUCING THEM * 
Melvillk Thurston Cook. 
Part VI. Flower and Fruit Galls. 
Galls affecting flowers and fruits are not so abundant as those 
affecting leaves, but in many cases the insect which produces 
flower or fruit galls also produces leaf galls. No sharp line of 
distinction can be drawn between flower and fruit galls, since the 
gall may form and mature without indication of fruit or may 
form in the flower and mature as the fruit develops. Thus far I 
have collected five species of flower and fruit galls representing 
three orders of insects. 
I. GALLS OF THE ACARINA. 
Phytoptus sp. — on Euphorbia corallata E. (Figures 70 ; 71a, 
b ; 72a, b). This mite produces galls on both leaf and flow'er. 
The structure of the gall is the same in both cases and is identi- 
cal with Phytoptus galls, previously described in Part I, (Figures 
8-1 1 ). All my specimens of this gall were well advanced. The 
structure of the leaf of E. corallata (Eig. 70) is typical. When 
attacked by the Phytoptus the leaf becomes very much modified 
by thickenings, ridges and convolutions (F'igures 71a, b). The 
palisade cells divide so that it is impossible to distinguish them 
from the mesophyll, and the intercellular spaces are obliterated as 
the result of the rapid cell division. The new cells are small and 
ver}’ rich in protoplasm, but gradually become filled with tannin 
as the gall approaches maturity. The tannin first forms in the 
outer and most exposed cells of the gall while the inner layers of 
cells retain their protoplasm very late. The Phytoptus restricts 
its attacks to these inner and more protected parts. From a study 
of these galls it is apparent that the Phytoptus is not working on 
Contributions from the Department of Zoology and Entomology, Ohio State Univer- 
sity, under the direction of Proi. Herbert Osborn, No. 17 . 
