190 INSECTS AFFECTING VEGETATION 



lieved to be single-brooded, and to hibernate in its galls in the wheat 

 stems in the larval stage, transforming to pupa and adult insect in 

 the following spring or early summer. 



The Wheat Straw-Worm. This insect is very closely allied to 

 the joint-worm. It is distinguished, however, by its habit in living 

 free within the hollow stems or culms of wheat, and producing no 

 gall or deformation in the walk of the stem, as do the former species. 

 Its work within the stem is indicated by the eaten and torn inner sur- 

 face, and as a rule it does not occur in as great numbers as does the 

 joint- worm. It winters in the stem in the pupal stage instead of the 

 larval stage, as does the joint-worm, and is double-brooded. 



The adults of the two broods of this insect are quite dissimilar 

 in appearance, and have been described as distinct species. The 

 adults, consisting of both sexes coming from the over-wintered pupa?, 

 are rather minute, and the females are wingless or with the wings 

 greatly aborted and functionless. The eggs of this brood are depos- 

 ited about the last of April or early in May near the embryo head of 

 the wheat, which at this season is only a short distance above the 

 ground. These develop and produce the adult of the second genera- 

 tion in June. This generation is much larger and more robust than 

 the spring generation, and consists entirely of females provided with 

 fully developed wings. They are therefore capable of flying readily 

 about and constitute the migratory brood. The eggs from this brood 

 of large-sized females are deposited in or near the joints of the straw, 

 more frequently near the second joint below the head. The worms 

 on reaching maturity enter the pupal or chrysalis stage in the fall 

 and emerge as adults the following spring. 



The damage from the wheat straw-worms is not often of a serious 

 nature, but is quite general, and is probably very commonly over- 

 looked on account of the concealed habits of the larvae, and this is 

 especially true of the wheat straw-worm, the falling of the grain 

 being often attributed to other causes. 



The remedy for both of these insects is in burning the stubble 

 which harbors the over-wintering stages. This burning may be done 

 either directly after harvest or at any time during fall or winter, or 

 prior to the earliest emergence of the adults, which may begin by the 

 latter part of March. 



The Wheat Bulb-Worm. The parent of the wheat bulb-worm 

 is a minute two-winged fly or gnat, not at all related to the Hessian 

 fly, except in its habit of breeding in wheat and various grasses, 

 and the damage due to it is doubtless very often confused with that 

 done by the more dreaded species. 



The wheat bulb-worm fly is a native American species, and 

 doubtless originally bred in various wild grasses. It is known to at- 

 tack timothy and blue-stem and other grasses, and also rye, oats, and 

 barley, as well as wheat. It is not nearly so destructive an insect as 

 the Hessian fly, yet sometimes causes considerable loss. The flies ap- 

 pear in September and October and deposit eggs (less than 0.025 of 

 an inch in length) on the young wheat plants. The pale watery- 

 green footless maggots hatching from these eggs work their way down 



