6 BULLETIN 986, U. S. DEPARTMENT OF AGRICULTURE. 



Although never believing in the old vegetarian theory of the 

 earlier entomologists, the writer decided to give this theory a test. 

 First a minute examination was made of the blackberry plants, in- 

 cluding all parts both in and above the ground. Not a single chigger 

 was found on them. Then the examination was extended to the 

 other plants growing on the vacant lots — goldenrod, several grasses, 

 and a number of common weeds. Each plant species was taken by 

 itself, specimens were pulled up, shaken over white paper, taken to 

 the laboratory, and even examined in parts with the microscope. 

 After several days of fruitless attempts to locate the larvae feeding 

 on plants the work was stopped, for evidently they could not have 

 been feeding normally on these, or at least a few of their enormous 

 numbers would have been encountered. 



About this time there appeared in this country the extensive paper 

 by Drs. T. Kitashima and M. Miyajima (7) entitled, "Studien ueber 

 die Tsutsugamushi-krankheit," in which is given, among other 

 things, a summary of the work on the life history and habits of the 

 Japanese chigger, Trombicula coarctata Berlese (J). These writers 

 claimed to have reared this chigger mite from field mice and to have 

 established the fact that it was normally parasitic on the same. A 

 few days later Dr. Miyajima, who happened to be visiting in this 

 country, called at the Bureau of Entomology while in Washington. 

 During his stay he reiterated his statement that the Japanese chigger 

 was normally parasitic on field mice and also said he believed that 

 it normally parasitized various other mammals. 



Following the conference with Dr. Miyajima. it was decided at 



once to investigate the small rodents which were known to exist in 



the vicinity and on the ground of the infested lots. A dozen traps 



were procured and trapping began with "these on September 13 and 



continued until September 24. In all, traps were set in 21 different 



situations, including 13 in the infested area and 8 on adjoining unin- 



fested ground. Small mammals, chiefly rodents, were caught and 



examined microscopically in the laboratory as follows : 



September 13 4 September 18 2 September 23 1 



September 15 3 September 19 1 September 24 1 



September 16 1 September 20 1 



September IT 2 September 22 1 



In all, 17 small mammals were caught, all within 11 days. Among 

 those obtained the following were determined by Dr. Ned Dearborn, 

 of the Bureau of Biological Survey: House mouse (Mus musculus) ; 

 common meadow mouse {Microtus p ennsylv aniens) ; short-tailed 

 shrew {Blarina hrevicauda) . 



Not only were the skins of these mammals examined carefully, but 

 the ears and some of the other parts were removed and washed 

 violently in alcohol and the washings examined. As a result of these 

 examinations not a single chigger was found. 



