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Stray Notes on Ticks. 



By F. No AD Clark. Read October i^^t/i, 1909. 



I HAVE given to my paper the title "Stray Notes," because I am 

 unable, as, indeed, it would be no easy task even for an expert, to 

 illustrate and treat of the British ticks alone, much less of the many 

 foreign genera and species. I will therefore endeavour to interest 

 you with a few typical examples. 



The study of ticks is an important one from the aspect of economic 

 zoology. Although popularly regarded as an insect it will presently 

 be seen that the tick is not an insect strictly speaking. In the tropics 

 ticks are intolerable pests to beasts, birds and reptiles, and are with- 

 out doubt the cause of a widespread number of diseases in cattle, 

 poultry, and in some instances man himself. Whether these are 

 conveyed by the \\cks per se, or simply as an intermediary for infec- 

 tion, had for some time been in doubt up till the researches of 

 Lounsbury, Wheler and others, who are now of opinion that specific 

 febrile diseases are certainly communicated to animals by their means. 

 As instances may be mentioned the destructive Texas cattle fever or 

 "redwater," East coast fever, "heart-water" in sheep and goats, and 

 in England " louping ill " in cattle. 



The Ixodoidea form a family of the Acarina or mites, included in 

 the class Arachnida, of which group the spiders, scorpions and mites 

 form the typical examples. 



It may be convenient here to give an illustration of the common 

 sheep tick or " ked " or " keb, " Melophngus ovinus (PI. IX, fig. i), 

 which is not a " true tick " but belongs to the order Diptera. When 

 these first appear they possess wings, but when located on a host 

 lose them either by biting or casting off, although while winged they 

 may live on birds, but it is evident to any entomologist that their 

 structure is very different from that of the " true ticks." 



Ticks may be regarded as gigantic mites, and they pass through an 

 incomplete metamorphosis from egg*(Pl. X, fig. 2) to larva (six-legged), 

 nymph (PI. IX, fig. 2), and adult (eight-legged). They are brown to 

 brown-black in colour and are in shape a more or less flattened oval, 

 according to the genus. The body is partly covered by a hard 

 shield, and has a false head or capitulum which carries two 

 palpi and the mouth organs, consisting of a hard transparent chiti- 

 nous labium, or hypostome provided with a tube for sucking blood 



* The &%% is spherical in shape and of a yellowish-brown colour. Fig. 2 of 

 Plate X illustrates the method by which the larva emerges, the shell being 

 split open from apex to base. 



