210 MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 



Happily, the breeding of these flies in excrement ordinarily 

 causes no menace to human health ; because (unlike the house- 

 fly) they do not commonly visit human habitations and human 

 foods, but confine their explorations as adults almost exclu- 

 sively to flowers out-of-doors. 



B. INJURIOUS HABITS. 



Few large families of insects are on the whole less detrimental 

 to human interests than the Syrphidae. Yet it is incorrect to 

 state, as some of our text-books do, that none of the species 

 are injurious ; for although the family includes no well-known 

 pests in this country, there are two important ways in which 

 the Flower-flies are injurious in the larval stage. 



1. As Crop-Pests. The few species which are phytophagous 

 are occasionally seriously destructive to crops. The most 

 notable of them in America is Toxomerus* politus which has 

 come to be known as the Corn-feeding Syrphid-fly. This 

 species has been reported as feeding on corn in abundance as 

 follows: New Jersey, 1885 (44), 1899 (53) and 1913 (42); 

 Florida, 1886 (44) ; Missouri, 1889 (45); Delaware, 1900 (50) ; 

 and North Carolina, 1913 (35). I found them (pupae) abund- 

 ant on field corn (in the axils of the leaves) at the Ohio State 

 University farm, September, 1915; and Professor Z. P. Metcalf 

 sent me larvae and pupae (attached among the glumes on the 

 tassels) from West Raleigh, North Carolina, in late August, 

 191 5 with the statement that they were again plentiful there. 



The species is evidently widespread and common on corn, 

 but only a few cases are known where its attacks were con- 

 sidered serious; notably in Florida and Missiouri (loc. cit.). 

 They feed on pollen grains and on the saccharine cells at the axils 

 of the leaves. The former habit might seriously interfere with 

 fertilization and the consequent yield of grain, if the larvae were 

 abundant; while the latter attack was stated to produce a wilt- 

 ing and browning of the lower leaves similar to the injury from 

 chinch-bugs. This species is not yet recorded from Maine but 

 will probably be found to occur within the State. The puparia 

 are often heavily parasitized which may explain why they are 

 not oftener seriously destructive. 



*Mesogramma. 



