ENTOMOLOGY 



C. T. VORHIES 



The chief activity of this department during the summer and 

 autumn months of the year 1918-1919 lay in continuing the investi- 

 gations planned and begun the previous year on grazing range 

 rodents, with special reference to the Large Kangaroo Rat, Dipoaomys 

 spectahilis. The chief base of operations for this work is on the U. S. 

 Range Reserve on the northwest slope of the Santa Rita Mountains. 

 Difficulties in securing some of the fencing materials needed, and 

 also in securing labor when wanted, owing to war conditions, de- 

 layed the completion of the fences for the experimental areas until 

 late autumn. It was expected, when plans were made", to have these 

 fences finished by July, 1918, in time for the summer growing sea- 

 son. However, the summer rains of that year were so scanty that 

 practically no grass growth occurred on the selected areas, but the 

 delay in fencing did not afYect the course of the experiments, which 

 were in many phases postponed one year by the unfavorable season. 

 Life-history and ecological studies of the Large Kangaroo Rat, and 

 to some extent of the Merriam Kangaroo Rat (Dipodomys merriami), 

 and of the jack rabbits and occasionally of other rodents, were con- 

 tinued throughout the year, resulting in the securing of considerable 

 valuable data. 



The fencing was finally completed in November, 1918, with 

 the assistance of two University professors while the University 

 was closed on account of the influenza epidemic. Approximately 

 eight hundred dollars were expended by the Forest Service in ma- 

 terials and construction of these fences under the cooperative agree- 

 ment whereby the U. S. Forest Service, the U. S. Biological Survey, 

 the Carnegie Institution, and the University of Arizona Experiment 

 Station are working on this grazing range project. 



As opportunity offered, the department also carried on the 

 work of building up the collection of Arizona insects. Two steel 

 cabinets containing four dozen Schmitt boxes were secured in which 

 to house the collection. Some investigation of the distribution of 

 the Arizona wild cotton (Thurberia thespcsioides) and of the native 

 boll weevil which lives upon it was conducted during the year. 

 This was undertaken with reference to the possible future bearing 

 of the results upon the extension of the area of cultivated cotton up 

 the Santa Cruz and Rillito valleys. 



