850 AN INTRODUCTION TO ENTOMOLOGY 



entire length. Veins Cu2 and 2d A coalesce at their tips, except in 

 Chalarus. In this genus vein Mi +2 is atrophied and the medial cross- 

 vein absent. Cells R and M are long. 



The flies hover in shady places. They are sometimes found on 

 flowers, and may be swept from low plants; our most common species 



Fig. 1 103. — Wing of Pipunculus. 



measure about 3 mm. in length, not including the wings. The larvas 

 so far as known are parasitic upon bugs. 



This small family is represented in North America by about 

 thirty species, nearly all of which belong to the genus Pipunculus. 



Family SYRPHID^ 

 The Syrphus-Flies 



The family Syrphidae includes many of our common flies ; but the 

 different species vary so much in form that no general description of 

 their appearance can be given. Many of them mimic h>Tnenopterous 

 insects, thus some species resemble bumblebees, others the honey- 

 bee, and still others wasps ; while some present but little resemblance 

 to any of these. 



The most distinctive characteristic of the family is the presence 

 of a thickening of the membrance of the wing, which appears like a 

 longitudinal vein between veins R and M. This is termed the spu- 

 rious vein, and is lacking in only a few members of the famil}^ ; it is 

 represented in Figure 1104 by a band of stippling. Vein R4+5 is 

 never forked; the tips of vein R4+5 and Mi +2 coalesce; and the first 

 anal cell is closed. 



The antennae are three-jointed; the third segment usually bears 

 a dorsal arista, bu^ sometimes it is furnished with a thickened style. 

 The face is not furnished with longitudinal furrows to receive the 

 antennas as in the Muscidae. The frontal lunule is present, but the 

 frontal suture is wanting. 



The adults frequent flowers and feed upon nectar and pollen. 

 Some fly with a loud humming sound like that of a bee, others hover 

 motionless except as to their wings for a time, and then dart away 

 suddenly for a short distance, and then restime their hovering. 



