1908 ENTOMOLOGICAL SOCIETY. 47 



OBSERVATIONS ON THE SORGHUM MIDGE. 

 By R. C, Treherne, Ontario Agricultural College, Guelph. 



Before commencing the discussion of my subject, I should like it under- 

 stood at the outset that the observations recorded have not yet been con- 

 firmed by repetition, and, no doubt, therefore, some of them may not be 

 entirely correct. The first study of the life-history of any insect is apt to 

 be wrong in many respects, as we find, for instance, was the case with the 

 first published statements made at the bejfinning of the Mexican Cotton-boll 

 Weevil investigations, I purpose, therefore, to give a mere outline of such 

 observations on the life-history, distribution and habits of the Sorghum 

 Midge as came under my notice during this summer of 1908, and crave 

 indulgence for the apparently inconclusive form of some of my records. 

 Again I ask you to bear in mind that the work was undertaken by a student, 

 the result of whose work still awaits proof. 



Sorghum is grown in Louisiana in comparatively small areas, nearly 

 every plantation, however, possessing a patch which rarely exceeds half an 

 acre in size. General, therefore, as the growing of this crop would seem to 

 be, it has for a considerable time been regarded as one which did not mature 

 its seed. Investigations into the cause of this non-maturity did not greatly 

 exercise the minds of the planters for the reason that the crop was not grown 

 for its seed production, but was grown rather for green feed and for the 

 manufacture of molasses. General theories were advanced as to the cause 

 of this non-fruitage, but the attacks of the Sorghum Midge on the ovaries of 

 the sorghum plant now seem to be the most potent and the main cause as 

 yet determined. Yet it would be incorrect to say that the failure of 

 sorghum to mature its seed in Louisiana was entirely due to the work of 

 this midge, for the reason that the Sugar-cane Borer, Diatroea saccharalia, 

 F., the moth Nigretia sorghieUa, Riley, the Sorghum Smuts, the English 

 Sparrows and I have no doubt yet other destructive agencies, are all means 

 which help to prevent the sorghum crop from maturing its seed in the 

 South. 



So far as we know, this insect was first mentioned and described by Pro- 

 fessor D. W. Coquillet in Bulletin 18, N. S. Bureau of Entomology, on 

 "A Cecidomyiid Injurious to the Seeds of Sorghum." His description was 

 taken from some specimens sent from Alabama in 1895. The midge seems 

 not to have attracted further attention until 1907, when Mr. C. R. Ball, 

 of the TJ. S. Department of Agriculture made a number of observations on 

 its destructiveness in Louisiana. During this summer of 1908, systematic 

 investigations on the life-history and habits of this midge, were begun, with 

 the result that Professor F. M. Webster, who has the matter in hand, pos- 

 sesses considerable data to verify and to resume work on, if bo desired, at an 

 early date next year. 



With the adult flies of this species, the two sexes are of practically the 

 same dimensions, the females, however, on a superficial examination, 

 appearing, on account of their length of ovipositor and somewhat plump 

 abdomens, to be the larger. The abdomens of both sexes are brick red in 

 general color, while their heads and thoraxes present black indications. The 

 antennae of the males are considerably longer than those of the females and 

 it is by this characteristic that the two sexes are most easily recognized, 

 The females are somewhat more sluggish in their movements than the males. 

 The males, on the other hand, are the more active and are usually seen on 



