TICKS OF THE BELGIAN CONGO. 



317 



The sexes are very distinct. In the male the dorsal surface of the body is covered 

 by a hard scutum, whereas in the female the scutum only covers a part of the body. 

 When the male feeds his body swells only slightly, when the female feeds her body 

 swells to a great size owing to her integument being highly distensible. Upon the 

 dorsal surface of the basis capituli note the two porose areas which characterize the 

 females of all Ixodid ticks. The structural points to note in a description of a tick 

 concern (1) the scutum : its size, shape, grooves, emargination, punctations and 

 colour ; (2) the capitulum : the shape of the basis capituli, the form of the palps and 

 the structure of the hypostome ; (3) the ventral aspect : position of the sexual orifice, 

 anus, anal grooves, plates or shields, and spiracle ; (4) the legs : the structure of 

 the coxae, trochanters, and tarsi. 



The nine genera of Ixodidae are Ixodes, Haemaphy salts, Dermacentor, Rhipicentor, 

 Rhipicephalus, Margaropus, Boophilus, Hyalomma and Amhlyomma (including the 

 sub-genus Aponomma). Their degrees of affinity are indicated by the following 

 scheme (Warburton) : — ■ 



Ixodidae 



Prostriata 



Metastriata 



Brevirostrata 



Group 1 



Longirostrata 



Group 2 Group 1 



Group 2 



1. Ixodes. 2. Haemaphy salts. 



3. Dermacentor. 



4. Rhipicentor. 



5. Rhipicephalus. 



6. Margaropus. 



7. Boophilus. 



8. Hyalomyna. 



9. Amblyomma. 



(Sub-genus 

 Aponomma) . 



The Ixodidae fall into two divisions, the Prostriata and Metastriata, of which 

 the first comprises but one genus, the second comprising the eight remaining genera. 

 The terms Prostriata and Metastriata refer to the position of the anal grooves which 

 in Ixodes surround the anus in front, whilst in other Ixodid ticks the grooves are 

 -either posterior to the anus or obsolete. 



