161 



State what you know about the Reproduction of Ticks. 



The male employs his mouth-parts to push the spermato- 

 phore (packet of spermatozoa) into the genital orifice of 

 the female. After fertilisation, the female leaves the host, 

 drops to the ground. She bends the capitulum so as to bring 

 it close to the genital aperture, and the bilobed cephalic 

 gland (Gene's Organ) is then protruded from under the front 

 edge of the shield ; it receives the eggs, one at a time, 

 and, rolling them round, covers them with a sticky secre- 

 tion. The eggs are then transferred to the rostrum, and 

 are laid in long masses in front of the tick. Parthenogenesis 

 occurs in Ticks. 



Write a General Account of the Life- History of Ticks. 



The female shrivels and dies after laying a batch of 

 eggs (except species of sub-family Argantinae). As many 

 a,s 15,000 eggs may be deposited by one female (e.g., the 

 Bont Tick). The active six-legged larva ("seed-tick" 

 or "grass-louse") ascends a blade of grass and waits for 

 a passing host, to which (first host) it fastens itself and on 

 which it remains two days or longer. When full of blood 

 the larva drops to the ground, moults, and changes into 

 a nymph with four pairs of legs. The nymph, acting like 

 the larva, attaches itself to the second host ; when replete 

 with blood, it drops off, and, remaining on the ground 

 for about three months, slowly develops into the adult 

 state. The adult lives on the third host. 



The three hosts may be different species of animals, or 

 different individuals of a species. Some ticks (e.g., Rhipi- 

 cephalus evertsi) require only two hosts ; others (e.g., 

 Rhipicephalus annulatus var. decoloratus) require only one, 

 the larva and nymphs not dropping off to the ground, 

 but remaining on the host. 



Name some Ticks which cause Disease in Man and Domesti- 

 cated Animals. 



Sub-family Argantinae (Soft Ticks). 



*-j-Ornithodorus moubata (Fig. 32). transmits Spirochaeta duttoni, 

 which is the cause of human tick-fever, or relapsing fever 

 of Tropical Africa. (See " Catechism," Zoology, Part /., 

 pages 46 and 47.) 



