Bias, the more conservative approach of Zumpt for this difficult 

 problem is utilized here. 



Theiler and Robinson (1953B) stress the difference between 

 this species and R. capensis Koch, 18/^., and R. serranoi Santos 

 Bias, 1950, two ticks not known to occur in t"He Sudan. In our 

 territory, R. sulcatus is easily differentiated from all species 

 but R. s. sangiiineus in its coarser forms. In northern Sudan 

 and usiially in Central Sudan, R. s, sanguineus is usually not 

 coarse enough to be confused wlthll ." Sulcatus , but in southern 

 areas both species may superficially resemble each other. Al- 

 though Nevimann's original description of R. sulcatus , together 

 with its illustration, was excellent, the~perplexing variation 

 in R. s. sanguineus and the previously unrecognized fact that 

 the^latter species has a pattern of large punctations, no matter 

 how densely punctate it may be, has long confused the real iden- 

 tity of R. sulcatus. We have spent dozens of hours trying to 

 differentiate among hvmdreds of collections of R. s. san^iineus 

 before the arrival of R. stilcatus specimens from Dr. Theiler 's 

 reared series. Afterwards, no question concerning their specific 

 differences remained. 



If one turns a questionable male obliquely to the light, 

 punctations of coarse R. s. sang\iineus will be observed to be 

 relatively shallow, mostly nondiscrete and sloping. Most im- 

 portant, a few n»re or less clearly defined rows of widely- 

 spaced, large, deeper, punctations will be noted among the shal- 

 lower interstitial punctations. In R. sulcatus no row formation 

 of large punctations is present, large punctations are numerous 

 and deep, and medium size punctations are also deep. Specimens, 

 if well preserved, should be briskly rubbed with damp tissue 

 paper until their surface shines in order best to distinguish 

 these characters. 



In females, the relative isolation of large punctations among 

 small or medium size ones usually differentiates R. s. sanguineus 

 from R. sulcatus in which large and medium size punctations are 

 indiscriminately scattered. The actual relatively greater length 

 of the sulcatus scutiam, which gives a first impression of being 

 even longer than it is, easily distinguishes most specimens. 

 Some variable R. s. sanguineus females may so closely approximate 

 this elongate sculal appearance that care must be used when apply- 

 ing this character. 



_ 764- 



