ENTOMOLOGY 



An extensive series of experiments in the control of the alfalfa 

 seed chalcis fly was planned in the spring of 1915, and arrangements 

 were made with eleven alfalfa seed growers near Buckeye and Chandler 

 for testing out the trap border control method mentioned in the last 

 report. The heavy rainfall in the late winter resulted in such variability 

 in the growth of alfalfa that in several instances the growers abandoned 

 their plans for producing a seed crop in the fields in which the tests 

 were arranged for, and in other cases the growers failed to follow the 

 plan agreed upon owing to a misunderstanding of their directions to 

 workmen. In all other cases the period of eight or ten days allowed 

 between the cutting of the borders and the main part of the field re- 

 sulted in too slight differences in the setting of seed pods. The outcome 

 was disappointing in view of the time and efforts made to arrange for 

 the cooperative experiments on a large scale. It is believed that in 

 further work along this line fourteen to fifteen days should be allowed 

 for the differences between the trap borders and strips and the main 

 part of the field. Continuous oversight of such experiments, which it 

 has not been possible to give so far, will be necessary before they can 

 be conducted satisfactorily. 



Work against the harvester ants in the ten-acre field near Phoenix 

 has continued. Conditions in the field were more unfavorable than 

 would occur in the average field. Owing to lack of care during 1915 a 

 heavy crop of foxtail grew in the field in the spring of 1916. This was 

 cut, and on May 12, when the season's work against the ants began, it 

 was lying on the field so as to make it difficult to find the nests. During 

 the season a total of 74 nests were found and treated, including many 

 weak colonies which appeared to consist of only a few individuals in 

 each case. The nature of the nests is indicated by the fact that an 

 average of only 1.3 ounces of London Purple were needed for each 

 nest during the season, whereas two seasons ago in the same field the 

 poison required for the 168 nests averaged 2.7 ounces each. The labor 

 and expense for the treatment has been increased disproportionately to 

 the possible injury from the ants owing to the splitting up of the 

 larger nests. Eliminating labor which should be charged to the ex- 

 perimental end of the work and putting all expenses on a basis of 

 practical farm work the cost for the year 1916 averaged about 64 cents 



