364 



SCIEXCE-GOSSIP. 



all. of the species of the genus Ixodes, and that in 

 such cases the sexual functions are performed 

 bv the mouth organs, all of which are inserted 

 with the exception of the palpi ( 2 ). This curious 

 anomaly has hitherto only been observed in two 

 species, loxdes reduvius in England and I. pilosus 

 in Cape Colony. The sexual orifice is absent in 

 the larval and pupal stages. The tarsus, or last 

 joint, of the first pair of legs is furnished with a 

 peculiar organ, known as " Haller's organ." which 

 is probably one of touch, hearing, or smell ;. but the 

 function is not understood. The second pair of legs 

 are the shortest, and the fourth pair the longest. 



The life history of a tick is sharply divided 

 between a free and a parasitical existence. In the 

 first state it lives absolutely without food of any 

 sort for prolonged periods, and passes its time 

 either in a semi-torpid condition, or else is actively 

 occupied in searching for a host on which to 

 establish itself. A headless female of Ixodes re- 

 duviusQ'). lacking all the month organs by which 

 feeding would be possible, survived over a year in 

 captivity, and was eventually lost. Argas persic-vs 

 is similarly stated to have lived without food for 

 three-and-a-half years in captivity ( 4 ). At such 

 times all growth is suspended, and the tick is 

 debarred from making any advance towards meta- 

 morphosis from one stage of its existence to another. 

 In the parasitical states life is supported by 

 sucking the blood of the host until the body of the 

 tick has, unless it is a male, become distended to a 

 considerable extent, and it is in this condition that 

 these pests are generally noticed owing to their 

 increased size. When replete, certain species fall 

 to the ground, and there remain while development 

 is proceeding inside the distended cuticle. After 

 a time the skin is split open, and the creature 

 emerges with its rostrum, shield, legs and other 

 external parts, increased in size and fully developed. 

 The body is proportionately diminished, so that 

 the animal's entire dimensions are practically 

 about the same as before ; but the new body, being 

 formed of a similarly distensible cuticle, is again 

 ready for repletion so soon as another host is 

 attacked. 



Some species never leave the host they have 

 first found, but pass all their metamorphoses upon 

 its person. In this respect the habits of different 

 Ixodidae vary considerably. Mr. Lounsbury, 

 Government Entomologist at the Cape of Good 

 Hope, informs me that the -red tick." Rhipi- 

 cepJiah/s evertsi, passes the first moult on, and the 

 second moult off, the host It. decoloratus, the 

 il blue tick," never leaves the host that it has once 

 found, after being hatched out of the egg, until, if 



(2) See R. T. Lewis, in the "Qnekett Microscopical Society 

 Journal " of October 1900. 



( 3) Mentioned by me in "Louping-ill and the Grass-tick " in 

 the " Boyal Agricultural Journal " of December 1899 (vol. x., 

 part iv.). 



(i) Referred to by C. Fuller in his " Bovine-tick Fever," 

 1896, p. 8. 



a female, it is ready in its turn for ovipositioD. 

 Argas redexus only attacks by night, after the 

 manner of the bed bug, a practice which may 

 enable it to escape destruction from the beaks of 

 the fowls or pigeons which are its usual prey, as at 

 such times they would be asleep, or at least in a 

 drowsy condition. Mr. Lounsbury says '-it ha~ 

 the peculiarity of undergoing an additional moult, 

 and, what is more, when adult, alternates egg- 

 laying with feeding, the interval being about the 

 same as between the moults." Ixodes redm 

 seeks a fresh host after each moult, but as yet 

 little is known of the habits of any other British 

 species. Eeferring to the South African -bont- 

 tick," Mr. Lounsbury writes : " females do not 

 appear to complete their engorgement until they 

 have mated.'" If this be so with I. reduvius, and 

 perhaps other species, it may account for the 

 numerous dead and half -distended specimens that 

 may generally be found on the host. 



The length of life depends mainly on the 

 climatic conditions, and whereas Messrs. Dixon i 

 Spreull state that RMpicepludus decoloratus. the 

 Texas cattle-tick, is only sixty days in passing the 

 whole period of its existence, it is probable that 

 our British species average about a year and a 

 half, varying largely according to circumstances. 



The damage done to stockowners by these pests 

 in other countries is enormous. Mr. Cooper Curtice 

 ;&ts : ( 5 ) " Cattle-ticks cause the quarantine of 

 eighty-one counties in North Carolina. The cattle 

 traffic in thirteen States and the Indian Territory 

 is seriously interfered with on account of the ticks. 

 Mr. P. E. Gordon. Chief Inspector of Stock for 

 the Government of Queensland, states in his Annual 

 Eeport for 189* that previous to that year no less 

 than £IL000 had been spent in that colony in 

 connection with the investigations and experi- 

 ments made in combating "tick," or "Texas 

 fever." The searching character of these investiga- 

 tions has probably proved the salvation of stock 

 raising in Australia, as they resulted in the dis- 

 covery by Mr. C. J. Pound. Director of the Stock 

 Institute, that inoculation by the blood of immune 

 beasts would produce immunity in previously 

 susceptible stock. 



From Cape Colony Mr. Lounsbury writes in his 

 Eeport for 1899 : " Heartwater," another tick-in- 

 oculated disease, '• seems to have gained fresh 

 impetus of late years, and is spreading by leaps 

 and bounds into the Midlands." "The market 

 value of these properties is depreciated by the 

 infection from 30 per cent, to 60 per cent., I am 

 reliably informed." This disease attacks sheep 

 and goats, and is carried by a tick named Am- 

 olyomma hebraeum. 



To the ravages caused by ticks abroad may be 

 added the damage done to sheep at home by 



(5) Begnlations for the Control of Contagions Diseases of 

 Live Stock, &c_ May 1st, 1900, ~Sonh Carolina Department of 

 Agriculture. 



