44 Guide to Insects and Ticks. 



oxen the deadly disease known as heartwater, when it bites a 

 healthy animal after having fed upon one that is suffering from 1 1 it- 

 disease. The organism that causes the disease has not been seen 

 in the blood of the vertebrate host, but experimental investigation 

 shows that it is not transmitted through the egg of the tick as aro 

 some other tick-borne blood-parasites of the genera Piroplasma 

 and Sj)inn-]i(ti'tn. 



The larva, nymph and adult of the bont tick feed on three 

 different individual hosts, dropping to the ground after each meal ; 

 the organisms imbibed with the blood of an infected host by tlu- 

 larva are transmitted to the second host by the nymph ; and 

 similarly, if a nymph' feeds on an infected host it may, when adult, 

 transmit the organisms to the third host. Mating of the ticks 

 occurs on the skin of the third host, and the female then feeds 

 until fully gorged; afterwards it drops to the ground, and in 

 course of time produces a vast number of eggs. 



