20 MONTANA EXPERIMENT STATION BULLETIN 366 



Effect of Mormon Crickets on Range 



No definite information has been available as to the effect 

 of Mormon crickets on the range. Through the increase in funds 

 made available during the past biennium, and with the coopera- 

 tion of the Bureau of Entomology and Plant Quarantine, and 

 the Forest Service, it was possible to employ Mr. Nolan Keil 

 who made a study of the relationship between Mormon crickets 

 and range plants. The work was carried on in the drainage of 

 Slim Sam Creek, Twp. 6n, r. lw, above Radersburg. All of these 

 observations were made where precipitation was abundant and 

 the crickets were not forced to eat certain plants because of 

 drought. Further, the crickets migrated to higher elevations be- 

 fore some of the later plants of the lower elevations appeared. 



The entire area in which observations were made was be- 

 tween 5000 and 6000 feet in elevation and on a general south 

 and east slope of an open range nature with occasional patches 

 of trees. The trees were both deciduous and evergreen. The 

 most common deciduous trees were Populus (cottonwood) , Salix 

 (willow) , and some Alnus (alder) . The most common ever- 

 greens were Pseudotsuga (Douglas fir) , Pinus (pine) , and Picea 

 (spruce) . 



The excellent moisture conditions persisting throughout 

 April, May, June and the first half of July increased the normal 

 length of life for many of the more succulent plants. As the 

 crickets preferred many of these to the grasses, this may ex- 

 plain to some extent the small damage to grasses this year. 



A collection of 203 species of range plants was made, of 

 which 55 were fed upon by Mormon crickets. Injury to these 

 plants was divided into feeding on leaves and feeding on flowers 

 and seeds. 



The 10 plants showing greatest injury to leaves, in order 

 of damage suffered, were: wild onion (Allium nuttallii), nodding 

 onion (Allium cernum), larkspur (Delphinium bicolor), bitterroot 

 (Lewisia rediviva), mouse ear (Cerastium arvense), shooting star 

 (Dodocatheon conjugens), violet (Viola nuttallii), dandelion (Tar- 

 axacum officinale), yellowbell (Fritillaria pudica), and yarrow 

 (Achillea millefolium). The first grass to appear in this series 

 was fifteenth in order of injury sustained. 



The 10 plants showing greatest injury to flowers and seeds 



