3 i 4 THE STUDY OF INSECTS 



nearly naked. The wings are much longer than the abdomen, and when 

 at rest they lie parallel to each other upon it. 



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

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

 measure about \ of an inch in length, not including the wings. The 

 larva? so far as known are parasitic upon leafhoppers. 



This small family is represented in North America by about thirty 

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



Family Syrphid^e 

 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 hymenopterous insects, 

 thus some species resemble bumblebees, others the honeybee, 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 membrane of the wing, which appears like a longitudi- 

 nal vein between veins R and M. This is termed the spurious vein, and 



R, /?* + J /? 4 + 5 



Fig. 556. — Wing of Erislalis. 



is lacking in only a few members of the family; it is represented in Fig- 

 ure 556 by a band of stippling. 



The adults frequent flowers and feed upon nectar and pollen. Some 

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

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

 a short distance, and then resume their hovering. 



The larvae vary greatly in form and habits. Some prey upon plant 

 lice, and are often found in the midst of colonies of these insects; some 

 feed in the stems of plants and in bulbs; others feed on decaying vege- 

 table matter, and live in rotten wood, in mud and in water; and others 

 live in ordure or in decomposing animal remains. Some are found in 

 the nests of ants; and some in the nests of bumblebees and wasps. 



The larvae of the genus Volucclla live as scavengers in the nests of 

 bumblebees and of wasps (Vespa). Some of the species in the adult state 

 very closely resemble bumblebees. 



The larvae of the genus Microdot! are hemispherical, slug-like crea- 



