The Ohio ^atura list, 
PUBLISHED BY 
The Biological Club of the Ohio State University. 
LIBRAR 
NEW YOU 
BOTANY 
QAROfcf' 
Volume XI. 
MAY. 1911. 
No. 7. 
TABLE OF CONTENTS. 
Metcalf— Preliminary Report on the Life-history of Two Species of Syrphidae 337 
Dickey — A Note on the Evaporation Gradient in a Woodlot 347 
Stover — Notes on New Ohio Agarics III 349 
Stover— An Ohio Station for Mitremyces cinnabarinus 350 
Stover — Two Unreported Ohio Species of Uneinula 351 
Wells— Meetings of the Biological Club 352 
PRELIMINARY REPORT ON THE LIFE-HISTORIES OF 
TWO SPECIES OF SYRPHIDAE. 
C. L. Metcalf. 
For many years it has been well known that the larvae of 
certain genera of Syrphidae feed upon plant lice (Aphidae) and 
are important agents in keeping these highly injurious insects in 
check. It is therefore believed that the following notes on the 
immature stages of two species of these flies, although incom- 
plete, are of enough interest to warrant this preliminary report. 
The work has been done under the able direction of the Pro- 
fessors of Entomology at the Ohio State University. It was 
taken up at the suggestion of Professor James S. Hine, to whom I 
am especially indebted for many valuable suggestions and 
criticisms. 
DESCRIPTION. 
Didea fuscipes Loew. 
LARVA. 
Length, 12-15 mm., width 5-6 nun., height 3-4 mm. The 
larvae are testaceous brown, footless, eyeless grubs. The head 
is not distinctly differentiated. Shape flattened, sub-cylindrical 
blunt at the posterior end, tapering and obtusely pointed in front 
when extended (Fig. 2.) The head segments are usually very much 
retracted when the larva is at rest giving to the anterior end a bluntly 
rounded appearance. The body is divided up into twelve more 
or less apparent segments, each, except the first two and the last, 
marked by several transverse folds of the integument. On the 
elevations of these folds in each segment are situated twelve long 
bristles in a transverse row. Of these the four nearest the mid- 
