35 



ON THE LIFE HISTOEY OF THE WHEAT BULB WOEM 

 {Meromyza ame'hcana, Fitch). 



This beautiful and interesting insect develops, as our acquaint- 

 ance with it improves, from the author of a conspicuous but in- 

 significant mischief (as it was known three years ago) to a dan- 

 gerous and occasionally very destructive secret enemy to wheat 

 culture in the United States. Having published an elaborate ac- 

 count of it in my Eeport for 1883, I give here only a brief 

 summary of the facts hitherto ascertained concerning its life his- 

 tory, with a report and discussion of the observations of the 

 present season. 



Previous to the publication of that article the species was re- 

 garded as single-brooded. I there gave, however, evidence of the- 

 existence of a second brood, summarizing the facts as follows:* 



From the above we may infer with certainty the existence of 

 two broods of this insect, the larvae of one appearing in autumn 

 and of the other in summer. It must be admitted also, that we 

 have not excluded the bare possibility of a third brood, at least 

 under favorable circumstances, which may develop in August and' 

 September in volunteer wheat and rye, or, possibly, in grass, or 

 some other plant. 



"Assuming that there is no such brood, we find the life history 

 to be about as follows: The eggs from the autumnal brood of 

 the flies are doubtless laid as soon as the wheat is ready for 

 them. From these eggs the worms hatch in September and Octo- 

 ber, doing usually much damage to wheat in fall, but continuing 

 the work in spring. By the middle of April they commence to 

 pupate, but do not all complete this transformation before the middle 

 of May. The pupal state lasts about a fortnight, the flies emerg- 

 ing from May 1 to June 1, or thereabouts. 



"Late in May and early in June the eggs for the next brood 

 are laid under and about the sheaves of the upper leaves of the 

 now heading wheat and rye; and these hatching, the larvae of the 

 second brood' make their way inward to the tender base of the 

 young pedicel of the head, just above the upper joint. Here they 



♦Pages 21 and 22. 



