246 THE MONTHLY BULLETIN, 



easily observed in the field. The maggot firmly supports itself by the 

 large posterior end, raises itself up and begins to blindly move its mouth- 

 end about in quest of food. If it touches a plant louse it immediately 

 lifts it into the air and suelvs it dry. This is very rapidly repeated, with 

 very disastrous results to the lice. When the larva is full grown it seeks, 

 some sheltered spot in which to pupate (transform into the adult fly). 

 This it may do on the stems or upon the surface of a leaf. The puparium 

 is a long, roundish, or oval, brown body, showing no signs of life. 

 The adult fly removes one end of the case to escape. The adults are 

 usually dark with transverse yellow bands across the abdomen. They 

 are very swift fliers and are often mistaken for bees. They are com- 

 mon around flowers, feeding upon the nectar and from this habit get 

 the names ''flower or honey flies." On hot days they are sometimes 

 very numerous and are called "sweat flies" in the Eastern States. 

 They deposit their eggs singly upon leaves and twigs which are infested 

 with plant lice and these give rise to the green larv^. 



While these insects do much to prevent the spread of the plant lice, 

 they are in turn preyed upon by other insects. Ants, which foster and 

 protect the plant lice, kill and carry off the larvae in large numbers and 

 greatly reduce their efficiency. Internal parasites also prey upon them. 



There are three species here which are doing good work in keeping 

 down plant lice : a very large species, Lasiophthicus pyrastri Linn., the 

 American syrphid, Syrphus americanus Wied. and the small species 

 Allograpta ohliqua Say. 



THE LARGE SYRPHID FLY. 



Lasiophthicus pyrastri Linu. 

 (Fig. 242.) 



General Appearance. — This is one of the larger syrphid flies, being 

 nearly one half of an inch long. The large compound eyes occupy most 

 of the head and are dark Indian red or brown. The face is yellow and 

 hairy, with median dark line ; antenna are black with long dorsal arista ; 

 thorax iridescent dark blue or green, covered with long, fine hairs or 

 pubescence; scutellum same color as the mesothorax; legs — coxa? dark; 

 femora dark with tips light; tibia^ amber or yellowish, slightly darker at 

 tips; tarsi dusky; abdomen velvety black with three pairs of marginal 

 curved transverse bands on the dorsum. These bands do not come 

 together in the middle and so really form six broken bands. The eggs 

 are very small and white. The larva?, when full-grown, are nearly three 

 fourths of an inch long and vary from light green to light brown in 

 color. The puparia are brown. 



Distribution. — This is an exceedingly common species found all over 

 the State. 



