Development of Ticks. 759 



The larvae migrate from the grass onto the bodies of cattle, and suck 

 their blood. After about eight days they change into pupas, and after 

 another eight days into nymphs, which after another molting develop 

 into sexually mature ticks. The nymphs, as well as the sexually mature 

 ticks nourish themselves with the blood of the host animal, following im- 

 pregnation however the female drops from the body of the cattle and 

 lays from 2000 to 4000 eggs in the grass, from which the larvae hatch 

 out in 3-4 weeks. They remain for a time in the grass, occasionally how- 

 ever they crawl on the skin of the pasturing cattle, and if the female 

 tick from which they originated has sucked infected blood during its 

 life, the larvae, and subse(iuently also the nymphs, inoculate the virus 

 into the body of the new host. Larvae and nymphs may also pass over 

 directly from affected animals to healthy cattle, in which case they 

 transmit the blood parasites in a direct manner. ( ?) 



The Ixodes ricinus s. reduvius transmits the infection, according 

 to the investigations of Kossel, Schlitz, Weber & Miessner, in a singular 

 manner ; the female tick dropping from the body of cattle lays in the 

 grass 100-1000 eggs, from which the larvae hatch out after an average 

 of six weeks. If the larvae attach themselves to the skin of cattle or of 

 other animals, they suck themselves full of their blood, and drop off 

 after 3-6 days, whereupon they change to nymphs on the ground inside 

 of four weeks. These attach themselves agani to the skin of a mammal, 

 from which they drop to the ground in from 3-5 days, where they de- 

 velop in eight weeks to sexually mature ticks, which again look for a. 

 host, where they suck the blood, and copulate. Therefore the total 

 development from the laying of the eggs until the dropping off of the 

 impregnated female takes about nineteen weeks, provided that the ticks 

 in their diff'erent stages of development always meet a suitable host and 

 that the weather conditions are favorable for their development. Ac- 

 cordingly the Ixodes distinguish themselves from the Boophilus among 

 others, in that they leave the host twice during their development, while 

 the Boophilus passes through all the stages of its development on one 

 and the same host. 



The eggs of the Ixodes reduvius are 0.50-0 55 mm long, and 0.27 to 33 

 mm. broad, of oval shape, and brownish-yellow to brownish-red in color. The 

 larva is 0.7-0.8 mm. long, 0.42-0.50 mm. broad, has a mite-shaped body, and three 

 pairs of legs; filled with blood it attains a length of 1.25 mm. and a breadth of 

 0.8 mm., when it takes on a blaekish-brown color. The nymph is 1.3 mm. long, 

 0.74 mm. broad; the body resembles the larva, but possesses four pairs of extrem- 

 ities; sucked full with blood it is about 2.0 mm long and 1.25 mm. broad and 

 of a dark gi-ayish color. The developed female is 3-4 mm. long and 1.5-2,5 mm. 

 broad; impregnated and sucked full with Idood it reaches a length of 10-15 mm, 

 and a breadth of 5-8 mm. ; it is then blue or ash-gray in color, sometimes slightly 

 brownish or yellowish, and has four pairs of extremities. The male is similar 

 in appearance, although somewhat smaller (Fig. 132). 



The larvae, nymphs, and the sexually ripe ticks may, with suffi- 

 cient moisture, remain alive for months outside of the animal body, and 

 they also withstand the cold of the winter without harm. In cold weather 

 they are benumbed, but as soon as warm weather appears they liven up, 

 and if conditions are otherwise favorable they continue in their devel- 

 opment. They are harmed however by direct sunlight. 



Experiments of infection conducted Avitli both species of 

 ticks showed that when larvae, hatched out from an infected 

 female in a glass container, are placed on the skin of healthy 



