THIRD ANNUAL REPORT OF STATE ENTOMOLOGIST. 187 



(1905). The difficulties attendant upon the extermination or even 

 the material reduction of this insect in back yards and other small 

 orchards within the city limits can scarcely be appreciated by those 

 who have not made a study of the life habits of this insect and of the 

 conditions in such orchards. A similar situation is to be found in 

 Flathead County. The writer has not had opportunity to make an 

 examination of the orchards where the moth has been working in 

 this county but has been informed that the pest has been greatly 

 reduced in numbers. The accompaning photograph (see plate III) 

 is of a backyard in Missoula. The photograph was taken to show 

 the method of banding, and the background and surroundings were 

 not particularly noticed in taking the photograph. The picture shows 

 admiralby the adverse conditions under which the State's officials are 

 working in fighting this pest. The cracks and corners in the board 

 fence and old door as well as the hiding places to be found in the 

 vegetation and in the unstirred soil make a combination of con- 

 ditions all but impossible of overcoming unless a complete renova- 

 tion is made. Contrast with this the photograph shown in plate 

 IV. Nothing is to be seen in this orchard but the trees, the soil 

 and the shadows of the trees. In such an orchard as this a much 

 greater measure of success may be obtained. 



LIFE ZONES IN MONTANA. 



The Division of Biological Survey of the Department of Agri- 

 culture has made a study of the temperature and other features that 

 control the distribution of plants and animals. Of the various fac- 

 tors aside from such obvious barriers as mountains and oceans it has 

 long been known that temperature is the most potent factor that 

 governs the limits beyond which particular species cannot go. In 

 his interesting and valuable paper on this subject, Prof. C. Hart 

 Merriam states that "the northward distribution of plants and ter- 

 restial animals is governed by the sum of the positive temperatures 

 for the entire season of growth and reproduction, and that the south- 

 ward distribution is governed by the mean temperature of a brief 

 period during the hottest part of the season." These statements 

 may be considered as laws. 



A minimum temperature of 60 degrees C (43F.) was assumed as 

 being the lowest at which plants were physiologically active and 



