348 



AN ECONOMIC ENTOMOLOGY. 



Fig. 399. 



vestiture is confined to the thorax or trunk, and such species are 

 sometimes of use in pollcnizint;^ flowers. I have found several 

 species about fruit-blossoms in sprini;, moving from flower to 

 flower, and, adiiering to the vestiture, I have found pollen grains 

 in considerable number ; so the insects are probably of some 

 importance in this direction. We have one very large species, 

 Eristalis tenax, appearing late in fall, often in houses, and so 

 closely resembling a honey-bee as to be generally mistaken for 

 one ; for which reason it has been called the " drone-fly." It is 

 frequent in greenhouses about the time 

 that chrysanthemums are in bloom, and 

 gardeners have assured me that poUen- 

 izing this flower is done by it entirely ; 

 hence they call it "chrysanthemum 

 flv." It is not at all unlikely that this 

 is the case ; indeed, it is even proba- 

 ble, though sufficiently direct observa- 

 tions have not as yet been made in the 

 matter. In this connection it is inter- 

 esting to find that the body vestiture 

 of the Syrphids is often composed of 

 spurred and branched hair, similar to 

 that found in bees, and in the " drone- 

 flv" this character is especially marked. 

 As widely divergent as the flies 

 themselves are the larvae and their 

 feeding habits. In fact, there is no sort 

 of agreement ; and while some are pre- 

 daceous, feeding upon plant-lice or 

 other insects, many feed in living or 

 decaying vegetable substances, or in 

 the foulest excrementitious material. 

 Those forms that most concern the agri- 

 culturist are the feeders on plant-lice, 

 and these may be found at almost any 

 time during the summer in almost every 

 aphid colony, busily engaged in lessening its numbers. The 

 larvcE are e-asily overlooked, as they are usually green or yel- 

 lowish in color, like the insects among which they feed. They 



^-tZ^ 



Body vestiture of Eristalii 

 tenax : a, entire hair; 5, c, d 

 parts of same; all greatly en- 

 larged. 



