159 



Prof. H. Garman, of the State College of Kentucky, who has studied this 

 insect and published his obiservations (Bulletin 30, Kentucky Agricultural Expe- 

 riment Station), gives also the following differences : " Under the microscope 

 another difference is apparent. The first two divisions and the under-side of those 

 following are roughened with very fine raised lines, directed crosswise of the body 

 in the wheat Bulb-worm-*^, while in the Frit Fly grub the first divisions and the 

 underside of those following in the region of the joints are roughened instead, with 

 numerous scale-like thickenings of the cuticle, with the hind edge of each thickening 

 finely toothed." 



2. The Wheat-stem Maggot, — This resembles the last in shape and structure, but is 



conspicuously different by reason of its colour, which is clear, glassy green, and 

 also by its much larger size, which is \ inch when full-grown. 



3. The Hessian Fly. — This is proportionately much broader than the other two, of a 



clearer white than the American Frit Ply maggot, and nearly always shows a 

 green stripe down the centre. Instead of the two hook-like Ijlack jaws, which 

 are present in the two previously mentioned maggots, the Hessian Fly larva has 

 a horny, forked organ, sometimes called the " breast-bone." Length of maggot 

 when full grown, ^ inch. 

 In the chrysalis stage the diff'erences are equally marked : 



1. The American Frit Fl.y.-^The pupa-case is shaped as shown above (Fig. 1), and is 



of a pale chestnut-brown. 



2. The Wheat-stem Maggot changes to a pale translucent green pupa. 



3. The Hessian Fly. — The piipfB>of this insect are of a deep, rich brown, like small 



flax-seeds, Fig. 4, and it is in this stage that farmers will most easily and surely 

 recognize the Hessian Fly when present. 



Co 



Fig. 3. 



Fio- 4 



-1. ij^. -r. 



The attacks of these three insects also differ somewhat, although the effect 

 upon the crop is of course similai*. The only known method of attack upon our 

 grain and grass crops by the Frit Fly is by the larvae attacking the young shoots 

 at the ground. The Qgg is probably laid near the base, on the upper side of the 

 leaf, and when it hatches the young maggot works its way down and destroys the 

 centre of the young stem. There are, however, sometimes as many as four or 

 five puparia found in a single dead shoot. These do not appear to always lie in the 

 centre of the stem, but between the bases of the sheathing loaves; but when there 

 is only one larva it is generally in the middle of the shoot. This attack is very 

 similar to an injury to grain by an insect of the same family Oscinis, which has been 

 known for many years in Europe, and which is sometimes very injurious to oats and 

 barley. 



The Hessian Fly (Fig. 3) lays its eggs in the crease on the upper side of the 

 leaves, and the 3'oung maggots work their way down to the heart of the plant just 

 inside the leaf wheieon they hatched. They lie there until full grown, and turn to 

 " flax seeds," two or three being frequently found round one stem. They have not the 



* = Wheat-stem Maggot. — I have used this name heretofore because the stem attack, which I have styled 

 "Silver-top," is the more conspicuous of the two injuries committed by this insect. 



