48 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



Fig. si.— I.\i>iies iKUci.iKiL'.s. ke.male, amj sti 



M.\L PL.\TE. 



host durino- this period. The male increa.ses but little in size, but the 

 female becomes enormously swollen and in about a month she is ready 



to drop ort' and deposit eo'ofs. 



Once in the blood of cattle the 

 parasite destroys the red blood 

 corpuscles, and causes a thinness 

 of blood, the ha'nmglol)in of which 

 appears in the urine. After death 

 the spleen and liver are found to Iv^ 

 o-reatly enlarg-ed. The most prom- 

 ising' preventive seems to l)e the 

 rcunoval of cattle from pasture for 

 one year. This pasture disinfection 

 m-AY be hastenel by cultivation for 

 one year, or grazino- it to sheep. 

 It has been noticed that southern 

 cattle may l)ecome innnune, and 

 with this hint a method of vaccina- 

 tion was devised for treating- north- 

 ern cattle when taken South. 



There are several other species 

 of ticks often found on cattle, but 

 none are known to carry the parasite of Texas fever. 



Of T)ei'inace)>f(>i' there are three or four s})ecies in this country, all 

 with the scutum more or less variegated with whit(> and brown. The 

 most connnon one is the ""dog tick,'' Dri'innctiiioi' 

 rYii'!<iJ>/]/s Say. and is our most widely distril)uted 

 •species. It is found on cattle, dogs, horses, rab- 

 ])its, and sometimes on man. On the latter it causes 

 no serious consequences, but i.> a source of nnicli 

 irritation. They are so tightly attached that it is 

 often impossible to remove them ^vithout either 

 lea\ing the head in the Hesh or else tearing out a 

 piece of the skin. The other species are similar to 

 the dog tick, l)ut are less common. One occurs on 

 the moose, and others on cattle, deer, tuid sheep. 



D. rdicuJatti.s Linnanis, a European species, is perhaps more fre- 

 ([uent in California than JJ. r(i/'i(d>/J!.'<. 



In the genus JLennqJiyxdlls 

 (formerly IiJi!j>ist<Hii<i) we have 

 one or two species that occur on 

 rabbits and other small manmials. 

 In Li'()de>< there are several spe- 

 cies; one is a European species, T. 



Fig. s'J.— Head of Ixodes 



Fig. S3. — Leg I of Ixodes: section through tae- 

 SV.S, /( Hallek's organ. 



rldnus Linnteus, that occurs occasionally on cattle. In Scotland this 

 •species often attack-^ sln^ep, and appears to distribute the germs of a 



