INSECTS INJURIOUS TO WHEAT. 



95 



stubble. From them the wingless females emerge in early 

 spring and j^lace their eggs upon the young wheat, usually 

 on or near the growing head. These become mature in 

 June, and from them the winged females develop. Singu- 

 larly, there are no males in this brood, they appearing only 

 in the spring, while in the summer brood the females are 

 so large and robust that they were at first mistaken for a 



Fig. 56. — Adult of Joint-worm {Isosoimi irlticl Harr.). a, female; 

 h, male; c, d, antennae of same; e, f, abdomens of same. 

 (After Riley.) 



separate species. ^' These deposit their eggs in or near 

 the joints of the straw, more frequently the second below 

 the head,'' becoming full-grown by fall, and passing the 

 winter in the stubble as jDupa?. The two species may also 

 be separated by their manner of injuring the straw. The 

 Joint-worm {tritici) makes more or less apparent galls in 

 the walls of the culm, while the Straw-worm [gr ancle) 

 forms no galls and but fewer individuals infest a straw. 



Owing to their small size and retiring habits these little 

 parasites of the wheat-plant — and they also infest barley 



