14 MONTANA EXPERIMENT STATION BULLETIN 408 



than desirable. As the amount of grain 

 going into storage and as the length of 

 time it is kept in storage increases, we can 

 expect continued increase in the impor- 

 tance of stored grain pests of all kinds. 

 The more common of these pests are 

 discussed in the Twenty-eighth Report of 

 the State Entomologist, Montana Agricul- 

 tural Experiment Station Bulletin 384 on 

 pages 12 to 16. Single sheet leaflets deal- 

 ing with these insects are also available 

 from the Montana Extension Service, and 

 may be obtained by asking for Circular figure's, sawtooth 



Series A— 18, 21, 24, 32 and 43. grain beetle. Greatly 



enlarged. 



OTHER IMPORTANT IXSECT PESTS, 1941-42 



NEW INTRODUCED LIVESTOCK PESTS 



primary screw worm. - The adult primary screw worm 

 (Cochliomyia americana C. and P.) is a bluish-green fly with a 

 striped thorax. It is a little larger than a housefly, and when at 

 rest the wings are held a little more directly over the back than 

 in the house fly or the larger blue bottle flies. 



Montana is far out of the normal range of this pest, and its ap- 

 pearance in this State in the summer of 1941 came as a surprise. 

 Apparently it gained entrance to Montana in the early spring of 

 that year through the introduction of cattle imported from Mexico. 

 No reports of this pest were received during 1942, and it is most 



unlikely that it would 

 be able to stand the rig- 

 ors of the winter in this 

 latitude. Trouble, then, 

 would be expected only 

 from southern cattle 



_, . _. . . brought into the State 



Figure 4. Primary screw worm taken , <? . , 



from a calf near Custer, Montana. Enlarged. ana rrom native cattle 



running with or near 

 them, and this difficulty would end with the advent of win- 

 ter. Some loss was experienced throughout the summer of 1941, 

 and possibly it may be years before it again appears in our region. 

 The adult females lay their eggs in the wounds of many do- 

 mesticated animals, injuries such as those caused by barbed 'wire, 



