COPULATION IN TICKS 673 



tube in the mature male contains formed spermatozoa, which, however, 

 are not active and do not become so until transferred to the female. 

 For an account of the mode of formation of the spermatozoa, which is 

 very complex, and of their structure, the reader is referred to Samson's 

 paper. 



After making several coils the vasa unite in the middle line and there 

 form a large lobulated organ, termed by Christophers the white gland 

 (Plate LXXXVI, fig. 6). The terminal portions of the vasa are usually 

 distended by large accumulations of spermatozoa and are easily ruptured. 

 The white gland, which appears to function as a seminal vesicle, is 

 lined by a single layer of high columnar cells. The accessory glands 

 which open into it appear to play some part in the elaboration of the 

 spermatophore. The number of such glands varies in different ticks; 

 in Argas persicus, for instance, there are five pairs (fig. 6). 



The spermatophore consists of a coiled ball of sperms surrounded by 

 a delicate membrane, external to which there is a tougher membrane 



which appears to be formed from the secretion of one 



, , . Spermatophore 



of the accessory glands. The shape of the mass varies ; 



in Ixodes ricinus, according to Samson, it is round, while in Ornithodorus 

 it is flask-shaped with an opening at the end of the flask. The sper- 

 matozoa pass out of the spermatophore and make their way into the 

 oviducts, where fertilization appears to take place. 



The act of copulation in ticks is unlike the corresponding one in 

 insects. It is best studied in the Argatini, which leave the host after 



each feed. If bred males and females are kept apart 



Copuifttion 

 until after the first feed, and then placed together in a 



petri dish, the act usually takes place at once. The male exhibits great 

 activity on first meeting the female, crawling rapidly and repeatedly over 

 her body and finally passing below her in such a way that the ventral 

 surfaces of the pair are in contact with one another. The male then 

 clasps the female in a characteristic manner, each pair of his legs being 

 in advance of the corresponding pair of the female. The mouth parts of 

 the male take the place of external genital organs for it will be noted 

 that the male has no such structures and these are passed over the 

 ventral surface of the female until the genital orifice is found ; they are 

 then inserted and withdrawn several times, apparently with the object 

 of dilating it. They are then finally withdrawn as the male passes a 

 little forwards until his genital orifice is opposite that of the female. A 

 spermatophore is now rapidly ejected and applied to the lip of the 

 orifice, and pushed in by the mandibles and hypostome. The male then 

 85 



