494 THE ANIMAL PARASITES OF MAN 



Texas fever in cattle is spread by Rhipicephalus annulatns, and Coast 

 or Rhodesian fever by R. appendiculatiis and R. simus. Their im- 

 portance as disease carriers amongst mammals is therefore consider- 

 able, and it may prove to be so for man. 1 They frequently attack 

 man, but chiefly, according to my observations, in their early stages 

 .in Europe; this is not so, however, abroad. The life-history of 

 a number of ticks has been clearly demonstrated. Mr. Wheler has 

 shown that in I.rodes rediimus it is as follows : the female deposits 

 her eggs in masses upon the ground, 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 Ixodidcv 

 they are covered with a glutinous secretion, by means of w 7 hich 

 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 \veeks, or it may only take eight weeks. In the case 

 of the bont tick a single female may deposit 15,000 or more eggs. 

 The process of egg-laying is described as follows by Mr. Wheler : 

 "When egg-laying is about to take place, the head is further 

 depressed till it rests close against the under side of the body. 

 In this attitude the end of the rostrum actually touches the genital 

 orifice, the palpi being at the same time widely opened out. Behind 

 the head and from beneath the shield, at what for the purposes 

 of explanation may be described as the back of the neck, a white, 

 perfectly transparent, delicate gelatinous membrane is brought down 

 through inflation, either with air or with a transparent fluid, above 

 the head, which it temporarily conceals. The end of this mem- 

 brane terminates in two conical points which appear to be covered 

 with a glutinous secretion, and at the same time an ovipositor of a 

 somewhat similar character, but only semi-transparent, is pushed 

 forward from the genital orifice. This latter is a tube, within which 

 is the egg. As the ovipositor projects it turns itself inside out, like 

 the finger of a glove, leaving the egg protruded at the end and lying 

 between the two finger-like points of the membrane. The membrane 

 and the ovipositor are then withdrawn each from the other. The 

 egg adheres to the former, which collapses through the withdrawal 

 of its contents, dragging the head forward and depositing it on the 

 top of the head. Neither legs, palpi, nor the organs of the mouth 

 take any part in oviposition, but after the collapse of the membrane 

 the palpi are closed and the head is raised, by which action the 

 egg is pushed forward to the front edge of the shield, forming 



1 This has been proved in Uganda so-called tick fever in man. 



