PACKABD.] THE ONION-FLY. 741 



wbereby some of the flies are liable to be always present in the garden, 

 in readiness to deposit their eggs; and maggots of widely-different sizes 

 are commonly met with in the same onion. 



"The eggs or 'fly-blows' are loosely placed upon the onion slightly 

 above the surface of the ground (Fig. — ), some of them being dropped 

 along the thin edge of the sheath or white membranous collar, which is 

 formed by the base of the lower leaf clasping around the stalk, and 

 others are crowded into the crevices between the bases of the leaves, 

 slightly above where they issue from this sheath. From two to six or 

 more egg's are usually placed on particular jilants here and there through 

 the bed. They are perceptible to the eye, being white and smooth, 

 four-hundredths of an inch (0.04) long, and a fourth as thick, and of an 

 oval form." When the minute maggot hatches from the eg<^, it works 

 its way downward iuside of the sheath, its track being marked by a 

 slender, discolored streak, till it reaches the root, on which it feeds till 

 it is wholly consumed, only the thin outer skin remaining. After eating 

 the bulb of one plant they attack the next, until sometimes a third or 

 a half of the bed is destroyed. 



The first indication that the plant has been attacked is afforded by 

 the leaves turning yellow and wilting. "On carefully digging up and 

 examining the affected plant, if it is young and the root small and 

 cylindrical, we commonly find it completely cut asunder as represented 

 in Fig. — , only the thin outer skin remaining, whereby the slightest pull- 

 ing upon the top draws it up out of the ground. Later in the season, 

 when the round bulb is beginning to be formed, as in Fig. — , we find a 

 hole perforated in its side, opening into a cavity in the interior, and the 

 earth around this perforation is wet and slimy, forming a mass of filthy 

 mud in which those worms are lying which are not engaged in feeding. 

 And by this interior cavity the central leaves of the plant are severed 

 from their connection with the fibrous rootlets, as shown in the figure, 

 whereby it is now these central and not the outer leaves which first 

 turn yellow and die, and all the upper portion of the root soon becomes 

 soft and putrid, while the bottom part, continuing to be nourished by 

 the fibrous rootlets, remains sound, and the worms now crowd into this 

 part to feed, whereby it sometimes presents a wonderful appearance, 

 being thronged with worms wedged together side by side in a compact 

 mass, all with their heads downward, eagerly consuming the last 

 remains of food there is there, and only the rounded hind ends of their 

 bodies exposed to view, these forming an even surface similar to the 

 cobble-stones of a street-pavement, as represented in Fig. — ." 



The maggot attains its growth, in summer, in about a fortnight, and 

 changes to a pupa either in the cavity in the onion or in "the wet, slimy 

 earth which is in contact with the onion. It here ceases to move, it 

 becomes contracted and shorter in length, its skin hardens and changes 

 to a tarnished yellow and finally to a chestnut color with a stain of 

 bla(;k at each end." This is the pupa-case, and the true pupa is inside. 

 In this condition it lies about two weeks before the fly escapes. 



In Essex County, Massachusetts, this fly is very destructive. The 

 maggots appear about the middle and last of May, and by the third 

 week in August the larvai are not found, only the pupa-cases. 



Description. — Tlie larva or raaggot is ehiniug, ilull white, cylindrical, taperiag to a 

 point in front, and when crawling and elongated, nearly the whole length of the body 

 becomes tapering. At the forward end the jaws appear under the skin as a short black 

 stripe. The hind end is cut off abruptly in an oblique direction, foruiiug a tlattened 

 Burtace, on which, slightly above llie center, are two elevated dots of a cinnamon-brown 

 color, and appearing somewhat like a pair of eyes; and around the margin are eight 

 small projecting teeth, of which the two lowest ones are largest ; and a little forward 



