Some Ectoparasites in the Soutli African Museum. 297 



connecting the closely approximated points of the long transverse 

 bands stretching inwards from the antennals. 



A. Anterior pair of spines thin Mackayia heteracanthus. 



A. A. Anterior spines peg-like B. 



B. Lateral bands with distinct median projecting incrassation on segments 6 and 7 

 only ; on 4 and 5 the bands are merely swollen on the inner median aspect 



Giebelia mirabilis. 



B.B. Lateral bands on segments 2-7 with projections on the inner middle 

 aspect C. 



C. Larger species (1'97) all over especially in the breadth of the prothorax and 

 abdomen. The central marginal pair of bristles on tergites 6-8 forming two 



divergent lines . . each bristle or hair being nearer to the marginal bristle 



before and below the stigma than to its neighbour Giebelia hexakon. 



Smaller species (1'81). The central marginal pair of bristles on tergites 6-8 iu 



parallel rows . . each bristle nearer its neighbour than to the stigmatic bristle 



Mackayia dimorpha. 



There are other very slight and possibly inconstant differences 

 between dimorpha and hexakon 2 2 , e.g. in the 1st antennal joint 

 (longer in hexakon). Again the entrant heads of the abdominal 

 lateral bauds are more angled on their outer aspect in dimorpha. In 

 hexakon they are almost round. 



The most remarkable differences are probably in the dimensions 

 of the head. 



These 2 2 are, however, somewhat difficult to separate. It does 

 not seem advisable to enumerate minute comparative differences as 

 their significance can be estimated only when more species are 

 known. We venture to think that many species of Giebelia and 

 Mackayia will yet be found on Tubinarial hosts. 



Special reference has been made in the above tables to six spines 

 or pegs on the head. As these are probably important throughout 

 the group, their arrangement in the four species now dealt with may 

 be graphically put thus : 



Giebelia lie.rakon 



Giebelia mirabilis <f . 

 Mackayia dimorpha 



