THE CARROT RUST FLY 11 



harvested at the normal time in the fall and taken from the field, the number of 

 rust flies which survive is reduced to a minimum. In 1929, when 74 percent of 

 the carrots left in the field over winter were infested, 79 rust fly pupae per square 

 foot of soil were found the following spring; but only 3.3 pupae per square foot 

 were found where heavily infested carrots were harvested. In the four years 

 when records were obtained, the number of pupae found where carrots were left 

 in the ground was 25 to 80 times more than where the carrots were harvested. 



DESCRIPTION! 



Egg 



White, oblong, about four times as long as broad, length varying from 0.6 mm. 

 to 1 mm., marked longitudinally by narrow ridges and furrows. Furrows between 

 ridges with circular pits so that sculpture resembles the surface of a peanut shell. 

 Constricted at one end, forming a knob or pedicel which is about one-third as 

 wide as the widest part of the egg. (See Plate 1.) 



Larva 



Length 6 to 9 mm., width 1 to 2 mm. When newly hatched, it is generally 

 colorless with white opaque spots, later becoming creamy white in color and 

 gradually darkening until, when full grown, it is a dark straw-yellow. The head 

 is sharply pointed and bears two prominent black hooks for gnawing. The rear 

 end is blunt and obliquely docked and bears the dark-colored caudal spiracles. 



Pupa 



Length 4.5 to 5 mm., width 1 to 1.25 mm., but varying considerably in size. 

 Bright amber brown in color, compact, and prominently obliquely docked behind. 

 When the adult emerges, this docked portion acts as a lid, opening at the posterior 

 tip and usually remaining hinged at the forward edge. 



Flies 



Length 4.5 to 5 mm. Males slightly smaller than females. Wings thin, slightly 

 iridescent, and extending nearly half their length beyond the abdomen. Abdomen 

 and thorax shiny, black, sparsely clothed with short yellowish hairs. Head and 

 legs pale yellowish brown. Eyes black. Basal joint of antenna same color as head, 

 but terminal joint black or tipped with black. Abdomen of male rounded at 

 apex; of female, sharply pointed at apex. 



LIFE HISTORY. SEASONAL HISTORY, AND HABITS 



HIBERNATION 



The carrot rust fly hibernates in a puparium in the soil within a few inches 

 of the plant in which the larva developed. In the field most of the puparia are 

 4 to 6 inches beneath the surface, although a few have been found deeper. 



In the fall of 1927 about a bushel of infested carrots was placed in a sunken 

 screen cage containing 10 inches of soil, and the larvae were permitted to enter 

 the soil naturally. The following April the soil in this cage was carefully removed 



'Adapted from Harvey. Maine Agr. Expt. Sta. Ann. Rpt. for 1893:178, with changes based on 

 study of specimens reared and collected at Waltham. 



