THE onion-fly: first indications of attack, 



175 



The pupa state ordinarily continues for about a fortniglit in summer 



when the front end of tlie puparium is 

 broken open, and the lly emerges and 

 escapes from the ground. The general 

 appearance of the ily is shown in Fig. 

 48 (after Fitch), and in Fig. -to, ante, 

 page 109, a more accurate view of the 

 wing is given, in enlargement. The 

 last brood of larvae pass the winter in 

 the pupa state, and the flies emerge in 

 earlv June, or about the time w'hen the 



Fig. 48. — The Onion-flj^, Phorbia " . . t j. 



CEPARUM (Meigen), enlarged. voung onions are in readiness to receive 



their eggs. 

 Commencement and Progress of an Attack. 

 The first indications of an attack by the larvae upon young onions, 

 the method of their procedure, and the progress of the injury, are so 

 well presented by Dr. Fitch (Eleventh Report on the Insects of the 

 State of New York, in Trans. N. Y. State Agricut, Soc, for 1866, p. 

 489) that we give it here : — 



'•The first indication which we have that our onion bed is invaded 

 by this enemy, we discover that two or three of the young plants are 

 wilted down and lying on the surface of the ground, perhaps changed 

 to a yellow color, and the plant next in the row to those prostrate ones 

 probably has its lower or outer leaf similarly wilted and prostrate, al- 

 though it is green and shows no wound or other indication of disease, 

 and the other leaves of this plant are erect, and to the eye appear per- 

 fectly healthy ; but on feeling them we find that they are soft and 

 flaccid, not firm and substantial, like those of the unaffected plants. 

 Thus by the feeling of the leaves we readily detect those plants which 

 have worms in their roots. 



'•' On carefully digging up and examining the 

 afiected plant, if it is young and the roots small 

 and cylindrical, wo commonly find it completely 

 cut asunder, as represented in Fig. 40, only the 

 thin outer skin remaining, Avhereby the slightest 

 pull upon the top draws it up out of the ground. 

 Later in the season, when the round bulb is be- 

 ginning to be formed, as in Fig. 50, 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 

 Fig. 49.— Young onion in feeding. And by this interior cavity the central 



attacked bv the onion- , , , i , -i /• ii • f 



worm (after Fitch). leaves of the plant are severed from their connection 



