ORDER ACARINA: THE TICKS 271 



supposed by its discoverer to be an organ of hearing, but is 

 considered by Nuttall to be olfactory. 



The genital pore in both sexes is situated in the middle 

 line, on the ventral surface, not far behind the capitulum. 

 Far behind it, in the same line, lies the opening of the 

 rectum. The spiracles are placed on conspicuous stigmata 

 which lie behind and dorsad of the coxae of the fourth, or the 

 third pair of legs. 



The mouth is deeply seated between the chelicerse and 

 the hypostome ; the pharynx is suctorial and leads by a 

 slender gullet to a large stomach, the capacity of which is 

 increased by paired caecal loops; these are nicely seen in a 

 well-preserved male tick, cleared and mounted in balsam. 

 The salivary glands, which are loosely racemose with long 

 tubules, are large ; they extend through nearly the whole 

 length of the body on either side, and open near the base of 

 the hypostome ; their secretion is supposed to be haemolytic, 

 and in some cases, from its irritant effects, to be poisonous. 



The excretory organs consist of two long Malpighian 

 tubules, which open into the isolated hind part of the gut, 

 and oi coxal glands which open on the coxae. 



The male tick is smaller than the female, and is often 

 conspicuously different in other respects. In fertilisation, 

 which may be effected while the female is attached, the 

 male inserts the spermatophores with the mouth-parts. The 

 eggs are laid in an inspissated mass on the ground, oviposition 

 being a prolonged affair, hundreds or even thousands of eggs 

 being extruded with great deliberation. According to Neu- 

 mann the entire parturition is completed, in the Ixodince, in 

 ten to thirty days. In some cases {Ixodince) the spent female 

 dies at once ; in other cases {Argantincs) she does not. The 

 term of incubation depends upon temperature, and according 

 to Neumann lasts from fifteen to forty days. 



The larva differs from the adult in having only three pairs 

 of legs, no stigmata, and of course no genital pore. Much 

 yolk is occluded in its gut, on which provision it can exist for 

 several months without other nutriment. The larvae hang 

 about in grass and herbage on the wait for a host (mammal, 

 bird, or reptile) to which they can affix themselves. After 

 imbibing blood for some days the larva, as a rule, drops from 



