T^he Ohio ^N^aturalist, 



PUBLISHED BY 



The Biological Club of the Ohio State University, 



Volume XII. MARCH, 1912. No. 5. 



TABLE OF CONTENTS. 



Metcalf— Life-Histories of Syrphidae III -177 



SCHAFFNER— A Revised Taxonomy of the Grasses 490 



TIiNE— Ohio Moles aud Shrews 494 



LIFE-HISTORIES OF SYRPHIDAE III. 



C. L. Metcalf. 



Syrphus Americanus Wiedemann. 



This is one of the most common species in the state, the adults 

 especially abundant about all kinds of blossoms in July and August, 

 as well as very early in the spring. The larvee are active and 

 greedy and found preying on a number of different aphids in large 

 numbers. It would seem to be one of the most important species 

 of Syrphidae in the state from an economic standpoint 



Egg. 



Elongated-ovate in outline, sub-cylindrical, narrower and 

 truncate at micropylar end, nicely rounded off at the opposite 

 end, broadest in front of the middle (Fig. 42); somewhat flat- 

 tened to the surface to which it is attached, slightly humped or 

 rounded up above (Fig. 41). Length about 0.9 mm., diameter at 

 middle about 0.3 mm. Color chalk white, hence conspicuous on 

 the darker surface of leaf or twig on which it is usually deposited. 



The entire exposed surface of the egg is beautifully sculptured 

 except a small region around the dark micropyle. This sculptur- 

 ing consists of microscopic projections of the surface arranged in 

 lines running longitudinally-obliquely around the egg. Each 

 projection consists of a long, slender, irregular body (seven or 

 eight times as long as broad) sometimes bent, with about twelve 

 to twenty slender arms reaching out in all directions from it. The 

 space between these bodies is roughly a half wider than the body 

 itself. Into these spaces the anns project, most of them meeting 

 similar projections from the same or another body, many branching 

 so as to form a delicate network of slender white anns between the 

 larger bodies. Fig. 43 is a fair representation of a small part of 

 the surface of the egg-shell, highly magnified. The projections 

 are chalk white, the depressions between them shaded, appearing 



477 



