THE ALFALFA CATERPILLAR. 7 



During the season of 1913 in Arizona the outbreak was heavier 

 in the Salt River Valley than it has been for several years — at least 

 the heaviest since the bureau began its investigations four years ago. 

 The report of the outbreak for this year is taken from the notes of 

 Messrs. R. N. and T. Scott Wilson, both of whom were located at 

 Tempe, in the Salt River Valley, this past year. The greatest amount 

 of damage was done to the fourth crop, although the third crop was 

 considerably reduced. The species reached destructive numbers in 

 the eastern part of the valley, especially in the vicinity of Chandler, 

 earlier than in other parts, so that the third crop was considerably 

 damaged and in some fields totally destroyed. On July 22 Mr. T. 

 Scott Wilson reported considerable damage to a field on Mr. Knep- 

 per's ranch, and stated that in large spots, perhaps as large as 50 

 to 100 yards across, the alfalfa was completely defoliated. On July 



29 the same observer states : " Mr. Lang's field, 3 miles north of 

 Chandler, shows more damage than any other field I have seen this 

 year. * * * The entire field is damaged, but on spots where the 

 land is rather poor the alfalfa did not grow as rapidly as in other 

 places, and after irrigation it came up quickly and at this tender 

 stage the worms attacked it, completely stripping it of leaves." 

 Mr. R. N. Wilson had previous to this, on July 25, made a similar 

 but more general note in which he says : " The butterflies are now 

 very numerous, and the larvae have stripped large patches in several 

 fields. * * * The most serious damage began in the central 

 part of the valley about a week or two weeks later than that de- 

 scribed in the foregoing notes and was much more severe. On July 



30 Mr. T. Scott Wilson reported very serious damage 6-| miles south 

 of Tempe. This field had about 25 to 50 per cent of the alfalfa de- 

 stroyed." Then, on August 7 : " In Mr. Harmon's field, 1| miles south 

 of Tempe, there are a great many pupae and larvae. The alfalfa is 

 almost completely bare of leaves." And on the same date he noted 

 that Mr. Olsons's alfalfa in an 80-acre field, 1 mile south of town, 

 was almost destroyed. Of course he meant the crop then present. 

 On August 14 he mentions seven different ranches that had almost 

 the entire fourth crop destroyed by Eurymus. A day later Mr. Wil- 

 son visited several fields south of Phoenix and found the fourth crop 

 here completely defoliated. It is thus seen that the damage ran into 

 thousands of dollars just to this one crop alone. One can hardly 

 anticipate exactly what would have been the resulting damage had 

 these caterpillars gone on unmolested and produced another genera- 

 tion of butterflies. Fortunately, however, the disease already men- 

 tioned appeared at this time and prevented a large percentage, pos- 

 sibly 90 to 95 per cent, from ever reaching the pupal stage. 



We thus have a history of the several outbreaks during the last few 

 years in these two larger valleys of southern Arizona and California. 



