2 BULLETIN 436, U. S. DEPAETMENT OF AGRICULTURE, 



DISTRIBUTION. i 



So far as known, the distribution of this flea-beetle is confined to 

 those areas of the southwestern United States that are normally 

 semiarid in chmate. As was stated in a preceding paragraph,, th© 

 observations by the writer and his associates have been confined to) 

 California, Arizona, and New Mexico, and the species has been col- 

 lected in practically aU of the lower altitudes throughout these 

 States. Collections in the higher altitudes show the species to be 

 usually absent. This is no doubt due to the annual rainfall, which . 

 usually increases with the altitude. An exception to this rule, how- 

 ever, was found by Mr. F. H. Gates, during the fall of 1915, when 

 he took several of the adult beetles at Prescott, Ariz., elevation 

 5,000 feet, where they were injuring Sudan grass. The writer, three 

 months previous to this, had made observations throughout northern 

 Arizona, stopping at Kirkland, Prescott, Ash Fork, Flagstaff, Hol- 

 brook, Wilhams, and Joseph City, aU of which are located at altitudes 

 over 3,000 feet, and although a careful and prolonged search was 

 made upon various known food plants, not a specimen was found 

 and no injury was apparent except at Prescott, where typical fecsd- 

 ing scars were found on corn. 



Through the kindness of Dr. F. H. Chittenden, the writer was per- 

 mitted to make use of certain records in the files of his office and 

 found that Prof. E. S. G. Titus had collected the species upon sugar 

 beets at Lehi, Utah, and Huntington Beach, Cal.; that Mr. E. L. 

 Crow found specimens at Yuma, Ariz.; and that Mr. H. O. Marsh 

 collected specimens feeding upon com at Anaheim, Cal.; the type 

 specimens were secured at Los Angeles, Cal., and Dr. George H. Horn 

 reported it as also occurring in Arizona. Only one other observation 

 has apparently been recorded;^ this was by Dr. A. W. MorrOl, who 

 mentions it as occurring upon Sudan grass at Phoenix, Ariz. 



ECONOMIC CONSIDERATIONS. 



To understand properly the nature of insect damage to crops 

 growing on irrigated tracts in the southwestern semiarid regions of 

 the United States one should know something of the existing condi- 

 tions. A tract of land is often found, varying from 200 to 100,000) 

 acres or more, entirely surrounded by thousands of acres of land 

 which is practically worthless from an agricultural standpoint; yet. 

 growing upon this land are weeds and grasses which serve as the 

 native food plants for certain insects. When this comparatively 

 small irrigated or dry-farm tract is planted to any crop, such as com, 

 milo maize, Kafir com, etc., a great many of these insects quickly 

 attack the new growing crops and feed upon them. Then, when 



1 Morrill, A. W. Report of the entomologist of the Arizona Commission of Agriculture and Horti- 

 culture. Ariz. Com. Agr. Hort., 6th Ann. Rpt., p. 33, 1914. 



