366 THE ANIMAL PARASITES OF MAN 



6. Fam. Ixodidcz (Ticks). 1 



Comparatively large acarines with a leathery skin ; they are flattened 

 in form, but after sucking blood the abdomen becomes spherical ; the 

 chelicerae are rod-like and possess a serrated terminal joint, bent hook- 

 like ; the median parts of the pedipalpi (maxillae) form a rostrum fur- 

 nished with barbed hooks (fig. 236) ; the maxillary palpi themselves are 

 club-like or rounded ; the legs are composed of six segments with two 

 terminal ungues ; often also with " sucking-discs " ; the stigmata are at the 

 sides of the body, posterior to the fourth pair of legs. The larvae are 

 six-legged. 



[The true ticks (Ixodidce) are all blood-suckers, and as far as is 

 known they do not take vegetable food at all. Not only are the 

 Ixodidce important as actual parasites, but they are most so on 

 account of the fact that they are the active agents in carrying 

 various diseases in animals and apparently in man. It has been 

 conclusively proved that the Bont tick (Amblyomma hebrceum) is 

 the carrier of the fatal " heart-water fever " so rife amongst sheep in 

 South Africa, that the dog tick (Hcemapsyllis leachi) is the agent by 

 which the protozoa that cause malignant jaundice in dogs is dis- 

 tributed, that Texas fever in cattle is spread by Rhipicephalus 

 annulatus, and Coast or Rhodesian fever by R. appendiculatus and 

 R. Simus. Their importance as disease carriers amongst mammals 

 is therefore considerable, and it may prove to be so for man. 2 

 They frequently attack man (vide p. 368) ; but chiefly, according to 

 my observations, in their early stages in Europe ; this is not so, how- 

 ever, abroad (vide. p. 373). The life-history of a number of ticks has 

 been clearly demonstrated. Mr. Wheler has shown that in Ixodes 

 reduvius it is as follows. The female deposits her eggs in masses upon 

 the ground, and then gradually reducing in size as the eggs pass out 

 until she finally remains a mere shrivelled empty bag and then dies. 

 The eggs are oval, golden-brown in colour and smooth ; in length 

 they are 0*59 mm. ; as in all Ixodidae they are covered with a 

 glutinous secretion, by means of which they adhere together in 

 masses. These egg masses may be deposited anywhere on the 

 ground, but amongst rough coarse herbage seems to be the favourite 

 place. The egg stage may last as long as twenty-two weeks, or it 



1 Pagenstecher, H. A., Beitr. z. Anat. d. Milben., 1861, ii., Lpz. ; Bertkau, Ph. 

 " Bruchstucke -a. d. Lebensgeschichte unserer /ecke" (Verh. d. nat. Ver. d. pr. Rheinl. 

 u. West/., Stzgsber., 1881, p. 145) ; Johannessen, A., "Acute Polyurie bei einem Kinde 

 nach dent Stiche eines Ix. ric." (Arch. /. Kinderhlkde., 1885, vi., p. 337) ; Blanchard, R., 

 " Penelr. de I'lx. ric. sous la pcau de I'homme " (C. R. soc. bioL. 1891 [9], p. 689) ; Neu- 

 mann, G., " Revis. de la fam. des Ixodides III." (Mem. soc. zooL, France, 1899, xii., 

 p. 107). 



2 This has been recently proved in Uganda so called tick fever in 



