642 MEDICAL ENTOMOLOGY 



douglasi, and the hare, Lepus dalli. The best methods of keeping these 

 animals in captivity are noted further on in connection with experiments 

 with Haemaphy salts. 



Experiments with Rhipicephalits sanguineus may be carried out on 

 the dog ; young pups just able to lap milk should be used, as they are 

 Genera Rhipicephalus easil >' handled - As already pointed out the dog tick 

 and Margaropus: R. requires three hosts, either of the same or of different 

 sanguineus, the dog species, to complete its life history. The larva remains 

 on the dog from 5 to 8 days, the nymph from 5 to 7 

 days and the adults from 8 to 10 days ; oviposition begins 2 to 4 days 

 after the female drops off and is completed in about a week. The larvae 

 hatch out in from 7 to 10 days and are ready to feed in from 2 to 3 days. 

 The cage (Plate LXXXII, fig. 3) suitable for experiments with this 

 tick is similar to the small one described above ; it measures 2 ft. 

 x 15^ in. x 16 in. If the worker wishes to experiment with Piropiasina 

 canis, a pup should be obtained and isolated for about a week in a cage 

 until all the ticks it harbours have dropped off; they can be collected by 

 placing the cage in a large cloth bag as shown in the figure on the plate. 

 The males should be picked off with a pair of forceps and destroyed ; it is 

 important to examine the insides of the ears, for this tick prefers this 

 situation to any other, and may very easily be overlooked. If the dog 

 is free from infection it should be transferred to another cage which has 

 been dipped in boiling water. The ticks for the experiment ma}- now 

 be liberated in the cage, first taking care to remove the underpan, 

 Otherwise some of the ticks may drop into the urine which collects in it 

 and will be drowned ; the wire foot-rest is left in the cage for the animal 

 to stand on. The method of liberating the ticks is as follows : Some 

 straw is dipped in boiling water to kill off stray ticks, and dried in the 

 sun; it is then placed in the cage near the animal and the ticks are 

 dropped on to it. This method of placing the ticks has man}- advan- 

 tages over any other. It imitates natural conditions, for ticks are 

 accustomed to crawl up blades of grass, sticks, etc., and to wait for a 

 passing animal ; they crawl about on the straw in the cage, and when the 

 dog touches it they transfer themselves to its body and soon become 

 attached. If ticks are dropped on to the body of the dog, they begin 

 crawling about, which irritates the animal and causes it to attempt to 

 dislodge them ; they may fall through the meshes of the foot-rest on to 

 the cloth below, and a long time, may elapse before they find their way 

 back again. In using straw there is the further advantage that there is 

 no. necessity to wait until each tick becomes attached, as must be done 



