702 



ARTHROPODA 



by several males. The female now becomes quiescent, and passes 

 out its ova, a process requiring a week or more to be completed. 

 During this process the head is forcibly flexed on the body, so that 

 the palpi lie on each side of the body, while above the head is the 

 prolapsed duct of the cephalic gland, forming a protuberant mass. 

 The ova are not as numerous as those of the cattle ticks, and are 

 generally laid in a loosely adherent mass. 



The six-legged larva hatches in less than a week. In Ornitho- 

 doros it appears to be quiescent, making no attempt to obtain food, 

 and in 0. mouhata does not leave the egg. In three or four days 

 it moults, and becomes the eight-legged nymph, which is an active 

 little creature, feeding readily. In Argas the larva is more vigorous, 

 and feeds. It appears as though there were great differences in the 

 life-history of the different species of the Argasidae. 



Fig. 320. — Argas persicus Latreille: Fig. 321. — Argas persicus Latreille: 

 Female, Dorsal Aspect. Female, Ventral Aspect. 



The adult Argasidae appear to moult many times as they grow 

 larger. They are preyed upon by insects. 



Genera. — ^The Argasidae are divided into four genera: — Argas, 

 Caris, Ornithodoros, Alectorobius. 



The diagnosis of these genera is as follows : — 



1. Eyes absent, body usually fiat, with thin borders, without 

 deep ventral grooves: (a) No groove behind anus — Argas; (b) trans- 

 verse groove behind anus — Caris. 



2. Eyes present or absent; body more or less distended, with 

 deep ventral grooves: {a) Without a fold of skin (sclerite) on each 

 side of palpi — Ornithodoros ; (b) with such a fold — Alectorobius. 



