298 



SUMMER MANAGEMENT 



the sheathed larvae crawl up grass or weed blades and stems, coming 

 to rest when the moisture evaporates and resuming the journey 

 when the vegetation is again wet. In this way they get up high 

 enough to be taken in by a sheep or lamb when grazing. After 

 being swallowed, they continue their development and attain ma- 

 turity in two or three weeks (Fig. 191). 



All that is known of the life history of the stomach worm has 

 been very briefly reviewed in the foregoing. So far as the writer 

 is aware, no one has yet determined how long an individual worm 



O.Iran 



O.lm 



FIG. 191. The ensheathed larva of the stomach worm on grass blades. (From Bureau of 

 Animal Industry Circular No. 93.) 



may live in the stomach of the host. If, as is maintained, none of 

 the eggs hatch in the stomach, then it would seem possible to 

 determine this point, and it would be valuable information. The 

 writer has observed very heavy infestation in sheep after they have 

 been confined continually in dry lots during the winter months. 

 Lambs born in the same dry lots were carried through entire 

 summer seasons without becoming infested. Therefore, it would 

 seem that the worms that were in the sheep when they came from 

 the pastures remained in them throughout the entire winter. 



Examining for Stomach Worms. Mature stomach worms are 

 from three-fourths to an inch in length. They look like a red and a 

 white thread intertwined. In conducting a post mortem for the 

 purpose of determining whether there is an infestation of stomach 



