The Ohio T\(^aturalist, 



PUBLISHED BY 



The Biological Club of the Ohio State Uni-versity. 

 Volume XI. MAY, 1911. No. 7. 



TABLE OF CONTENTS. 



Metcalf— Preliminary Report on the Life-history of Two Specie.s of Syrpliidae 337 



DiCKEV— A Note on the Evaporation Gradient in a Woodlot 347 



Stover — Notes on New Ohio Agarics III 349 



Stover— An Ohio Station for Mitremyees cinnabarinus 350 



Stover— Two Unreported Ohio Species of Uncinnla 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 lar\'ae of 

 certain genera of Syrphidae feed upon plant Hce (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 man}^ valuable suggestions and 

 criticisms. 



DESCRIPTION. 



Didea fuscipes Loew. 



LARVA. 



Length, 12-15 mm., width 5-6 mm., 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- 

 337 



