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STATE BOARD OF AGRICULTURE. 



all the joints from the top to the bottom. In the case of the flj, the in- 

 jury is due to the presence of maggots and flax-seeds between the true 

 stem and the leaf-sheith. The joint-worms burrow inside the walls of 

 the stem itself, causing it to become swollen and full of cavities and to 

 take on a woody structure toward nmturity. Fig. 23 shows a char- 

 acteristic straw, the swellings showing the number of little cells present. 

 lOach cell contains a tiny larva, Avhich later changes to a pupa and later 

 to an adult, winged, wasp-like creature of very small size. This adult 

 pierces the straw of a growing young wheat plant and deposits her eggs 

 for the next generation. 



The thickening of the straw interferes, of course, with the proper fill- 

 ing out of the head and also renders the straw brittle. While wheat 

 attacked by joint-worms is not so likely to lodge as that harboring 

 the fly, it is apt to produce shriveled berries, often cutting down the 

 jield very materially. None of the varieties which we have examined 

 seem to be resistant to the attacks of the joint-worms, and in our plots 

 we have examined over a score of different varieties. 



One brood each year is the rule, the eggs being laid in the yonnii- 

 growing plants, and the winter being passed in the cells made in tlw 

 straw. 



. FiQ. 20. Wheat Joint-worms; pupae ia straw en.arged (Original). 



Often the first intimation of trouble that the farmer has, is when 

 he discovers that the wheat is shriveled after threshing. He may blame 

 it to rust, or he may notice quantities of short sections of woody straw 

 which fall out by themselves, and which may cause him to question the 

 matter further. These short sections of woody straw are quite char- 

 acteristic of joint-worm work, and to the experienced eye immediately 

 point to the cause of the trouble. 



The adult insect that comes out in the spring, is a member of the 

 order of wasps, but so small that it would take a number to bulk as 

 large as a mosquito. The color for the most part is black. There are 

 four wings, and in the place of the sting is a slender tool for laying the 

 eggs. If it so happens that young wheat plants are accessible when 

 the adults emerge, they are immediately utilized as repositories for 

 eggs. 



