36 



brooded; that the eggs are laid by the adult upon the young wheat 

 in autumn ; that the larvae hatch and hibernate within the stem, 

 pupating in May and emerging late in that month and early in June. 

 They leave the stem, in fact, at about the time the young Isosoma 

 tritici commences its attack upon the wheat, and consequently these 

 two species, although specifically clearly distinguished, nevertheless 

 alternate like two broods of the same form. 



Concerning the distribution of this species, it can, at present, only 

 be said that it occurs in Western and Southern Illinois and in parts 

 of Indiana adjacent. As this insect inhabits the wheat only during 

 the period of the growth of the plant, escaping before the grain is 

 harvested, and passing the interval as a free imago, it is difficult 

 to see how its injuries may be prevented, unless, indeed, late sow- 

 ing, as practiced for the Hessian fly, may be found to affect this 

 straw-worm also. 



2. The Lesser Wheat- Stra.w Worm. 

 (Isosoma tritici, Eiley.) 

 Order Hymenoptera. Family Chalcidid.e. 



(Plate I, Fig. 5.) 



Observations made during the present season add one or two 

 points of interest to the life history of this destructive species. The 

 period when it begins its injuries has heretofore been a matter of 

 inference, but it was this summer found by Mr. Garman at work in 

 the wheat as early as June 5, many of the larvae being at this time 

 only a millimetre in length, and evidently but recently hatched. 

 The exact character of the injury produced by these young larvae is 

 well illustrated by the accompanying figure, exhibiting the cavity 

 from which a very small straw worm was removed. 



The parasitism of Eupelmus allyni upon this species and Isosoma 

 hordci has been placed beyond question by recent observations of 

 Prof. French, reported in the Canadian Entomologist for July, 1884, 

 pages 123 and 121. As evidence on this point, he says : 



"A single joint of rye containing several galls formed by Isosoma 

 liordei was put into a bottle and corked up, so that no insects could 

 get out or in. In due course of time a specimen of E. allynii was 

 found in the bottle, and the hole from which it had gnawed its way 

 out of one of the galls was plainly to be seen. Afterward the other 

 galls gave forth I. hordei. In this case there could be no question 

 but that the specimen of E. allynii came from the gall made by 

 I. hordei. If no hordei had hatched from the other galls, this would 

 have been evident, for the galls made by this species are too char- 

 acteristic to be mistaken by any one at all familiar with their work. 



I have bred quite a number of this species from the inside of the 

 stems of wheat ; and in all cases they came from the cavities in- 

 side the stalk that had been gnawed by Isosoma tritici. Though 

 this species of Isosoma makes no gall, its manner of eating the 



