LIST OF ILLUSTRATIONS. 23 Figs. 1-43.-Stigmal plates of Dermacentor. Plate. Fig. 1.-D. reticulatus, male, from Europe.. 1 Fig. 2.-Ditto, female, from Europe. Fig. 3.-D. electus seu variabilis, male, from North America... Fig. 5.-Ditto, female.... Fig. 6.-Ditto, section..... Fig. 7.-D. occidentalis, male, from California. Fig. 8.-Ditto, female.... Fig. 9.-D. andersoni, male, from Montana.. Fig. 10.-Ditto, female, from Montana.. Fig. 11.-Ditto, section...... Fig. 12.-Ditto, isolated goblet.. Fig. 13.-Ditto, isolated hair near margin of plate.... Fig. 14.-D. venustus, male, from Texas.. Fig. 15.-Ditto, female, unmounted.. Fig. 16.-D. paruma pertus, female, from California.. Fig. 17.-D. parumapertus marginatus, male, from Arizona.. Fig. 18.-Ditto, female...... Fig. 19.-Ditto, female, from New Mexico.. Fig. 20.-D. nigrolineatus, male...... Fig. 21.-Ditto, male, from Oklahoma.. 4 5 5 6 6 7 8 9 9 10 10 11 11 12 12 13 13 14 14 15 15 16 17 18 19-20 21 22 23 23 Fig. 22.-Ditto, male, from New York. Figs. 28 and 29.-Ditto, male, right and left plates, from Montana Figs. 30 and 31.-Ditto, female, right and left plates, from Montana Figs. 44-48.-Entire body. Fig. 44.-D. andersoni, male, ventral view, from Montana Fig. 45.-Ditto, dorsal view.... Fig. 46. Ditto, young female, dorsal view.. Fig. 47.-Ditto, ditto, ventral view...... Fig. 48.-Ditto, hexapod larva, ventral view.. Plate. 30 30 31 31 29 Figs. 49 to 70.-Outlines of capitulum and digit of Dermacentor. Figs. 49 to 50.-D. reticulatus, male and female.............. 32 Figs. 51 to 52.-D. electus seu variabilis, male and female.. 32 Figs. 58 to 59.-D. parumapertus marginatus, male and female... 33 Figs. 82 to 100.-Dorsal view of terminal portion of trochanter I of Dermacentor. Figs. 82 to 83.-D. reticulatus, male and female...... Figs. 84 to 85.-D. electus seu variabilis, male and female.. Figs. 86 to 87.-D. occidentalis, male and female... Figs. 88 to 89.-D. andersoni, male and female... Fig. 90.-D. venustus, male....... Figs. 91 to 92.-D. parumapertus marginatus, male and female.. Figs. 95 to 96.-D. salmoni, male and female..... Figs. 97 to 98.-D. variegatus seu albipictus, male and female... Figs. 101 to 119.-Coxa I of Dermacentor. 36 36 36 36 36 36 36 36 36 36 Figs. 101 to 102.-D. reticulatus, male and female.............. 38 38 38 38 38 Figs. 110 to 111.-D. parumapertus marginatus, male and female.. 39 39 39 Figs. 116 to 117.-D. variegatus seu albipictus, male and female.. 39 39 Figs. 120 to 134.-Intercoxal fields of Dermacentor. Figs. 120 to 121.-D. reticulatus, male and female..... Fig. 128.-D. parumapertus marginatus, male. Figs. 129 to 130.-D. nigrolineatus, male.. Figs. 131 to 132.-D. salmoni, male and female... Plate. 40 40 41 41 42 42 42-43 43 43 SUMMARY. The specific determination of ticks is attended in many cases with considerable difficulty. In view of the importance of these giant mites as transmitters of disease, every newly recognized character which can be utilized in classification is of value. In the present paper the microscopic structure of the stigmal plates is shown to be a taxonomic character of considerable importance in the genus Dermacentor. The species of Dermacentor which has been shown experimentally by King and Ricketts to act as transmitter of Rocky Mountain spotted fever in Montana is Dermacentor andersoni. The tick which Salmon and Stiles (1901) considered identical with Dermacentor reticulatus of Europe is shown to represent a new species, Dermacentor salmoni. For bibliographic references, see Stiles & Hassall, Index Catalogue of Medical and Veterinary Zoology Bull. 39, U. S. Bureau of Animal Industry. (8) |