G. H. F. Nutt ALL 
4:39 
[The only author who has studied the biology of R. bursa is 
Motas (1904, pp. 33-39) who demonstrated that the tick is the 
vector of piroplasmosis in sheep. He states that the disease occurs 
in May to November in Roumania, the sheep being then found 
heavily tick-infested. The ticks are chiefly found attached to bare 
parts of the sheep’s skin, notably about the axillae, prepuce, vulva 
and anus, the anterior part of the abdomen and inside the ears. 
I shall quote this author’s data in extenso ; merely rearranging 
them in conformity with the scheme adopted in this paper. 
R. bursa is a two-host tick, feeding upon one host as a larva and 
nymph and upon the second host as an adult. The larvae, ixnder 
experimental conditions, attach themselves to sheep upon the face 
and about the base of the ears, becoming fully gorged in about 
8 days; they then appear red, owing to the ingested blood; they 
remain attached to the host although they have ceased to feed, 
aiid, after a period of 2M: days, they assume a dirty white 
colour. After a further period of 1-2 days, they moult (whilst 
upon the host) and emerge as nijnvplis which reattach themselves 
at the same spot where they fed as larvae. The nymphs gorge 
in 10 days, attaining a length of 3-3-5 mm., and 1-2 days later they 
abandon the host to undergo metamorphosis to adixlts upon the 
ground. The duration of parasitism depends to some extent on the 
place of attachment upon the host. The adult ($), if fertilized, 
feeds upon the host for 7-8 days; if unfertilized, he states, that 
the females do not feed (which is wrong, vide infra) ; the d does 
not seem to wander about upon the host (this is incorrect). 
If an isolated male is detached and placed near an attached 
but unfertilized female, copulation occurs quickly and the female 
now proceeds to feed rapidly. Motas states that there is a marked 
difference in the proportion of the sexes, there being barely 1 d to 3 ? 
(my results q.v. give no such great disproportion). That the sexes 
are ready to feed when placed together upon the host is clear from 
his statement that a day after he had placed 50 adults on a ram 
16 (5 d, 11 ?) were found attached. Metamorphosis lasts from egg 
to larva 20-30 days, from larva to nymph (upon the host) 11-14 
days, from nymph to adult 45-55 days (in cool weather). Longevity: 
larvae survived unfed for 2-2^ months and then attached themselves 
readily to sheep. 
Motas first succeeded in infecting a sheep with piroplasmosis 
by removing 50-60 adult ticks (which did not appear as yet to 
