igio] Pediculoides Noxious to Man 39 



season, has varied from one to ninety-five per cent. Here, too, 

 we have found the mite generally in the cells in the straw occupied 

 by the joint worm larvae. It has been found that in central Ohio, 

 September sown wheat was much more seriously affected by the 

 joint worm than that sown in October, and also that the infesta- 

 tion is worse in both cases on poor soil than on that of an average 

 degree of fertility, and still less on good soil. The infestation was 

 invariably worse in fields lying adjacent to or where wheat had 

 been grown the previous year. Another interesting fact was 

 revealed, and that is that fall plowed fields showed the least 

 infestation of all. Therefore, it appears that moderately late 

 sown wheat on good soil and on land not devoted to wheat the 

 previous year, nor lying adjacent to such fields, has escaped with 

 the least injury, and that less difficulty with the dermatitis is 

 experienced where such wheat has been threshed from the field 

 and as soon as possible after the grain was harvested. As the 

 joint worm winters over in the stubble, where this can be burned 

 during the fall, winter or spring, the destruction of the pest in the 

 field will be complete. Where this cannot be done, much good 

 may be accomplished by raking over in the spring the last year's 

 stubble fields and burning the stubble thus collected. So impor- 

 tant are these measures that practicing physicians might almost 

 include them with their prescriptions for this painful skin disorder. 



Explanation of Plates. 



Plate III. 



Fig. 1. Pediculoides vcntricosus Newport, ungravid 9 • Stage in which the 

 mite is both migratory and predatory and in which it attacks humans. From 

 photograph by Dr. Jay F. Schamberg. Greatly magnified. 



Fig. 2. The Angoumois grain moth, Sitotrosa cerealella Ohv., a, eggs en- 

 larged; b. b., bernels of wheat infested by larvae; c, larva, enlarged; d, pupa; 

 e, moth with wings spread; /, same with wings closed as at rest. Figs, b.b., ori- 

 ginal remainder, after Chittenden, Farmers' Btilletin, U. S. Dept. Agrictilture, 

 No. 45, p. 6. 



Fig. 3. Pediculoides ventricosus, gravid 9 ■ Greatly enlarged. Redrawn 

 from Brucker. 



Plate IV. 



Illustrating various forms of the dermatitis lesions caused by attacks of 

 Pediculoides ventricosus. From Photographs by Doctor Schamberg. 



Plate V. 



Fig. 1. Lesions caused by bites of Pediculoides ventricosus, in experiment 

 of Dr. Joseph Goldberger. From drawing by F. H. Wilder. Courtesy of Public 

 Health and Marine Hospital Service. 



Fig. 2. Showing reduction in yield of wheat attacked by jointworm, 

 Isosoma tritici Fitch. The tube at left contains yield from 100 heads from tmin- 

 fested straws: tube at right contains yield from 100 heads from infested straws. 

 Photographed by W. J. Phillips, Bureau of Entomology. 



Fig. 3. Showing attack of joint-worm, Isosoma tritici, in field. Note the 

 enlarged and distorted stems. From photograph by Geo. I. Reeves, Bureau 

 of Entomology. 



