October, '11] WOOD: TICK PARASITES 429 



The percentage of parasitism varies considerably in the same locahty. 

 We have been able to secure at times an abundance of parasitized 

 ticks at Corpus Christi, Texas, while at others, though it may have 

 been very near the same season of the year, either no nymphs were 

 found or the nymphs found were not parasitized. 



The records in the table show the production of about one male to 

 three females. As may be seen the proportion of males to females 

 in a single nymph varies considerably, although it usually happens 

 that there is an excess of females and in no case has the proportion 

 of males exceeded that of females. The maximum number of parasites 

 per tick was seventeen, the minimum three and the average eight. 

 It took from twenty to sixty-seven, with an average of thirty-two 

 days from the date of collection for the adults to emerge. 



Description of Parasitized Nymph 



For several days after being parasitized the nymph appears normal. 

 The first indication of parasitism is swelling, soon followed by an 

 irregular striped appearance (See PI. 17, Fig. 2) caused by the larvae 

 of the parasite as seen through the nymphs' skin. This appearance 

 gradually passes away as the body fluids are taken up by the 

 parasite. Just before emergence, the front end of the body is black 

 and the posterior part yellowish translucent. This is more pro- 

 nounced in some cases than in others. 



Artificial Parasitism 



Early attempts to breed the parasites proved failures. Mr. W. A. 

 Hooker's trials gave negative results, as did also the author's early 

 tests. This was probably due to the extreme heat when the attempts 

 were made. Our efforts finally proved successful and it was found 

 very easy to breed the parasite, using Rhipicephalus sanguineus as 

 a host. It si quite likely another generation might have been bred 

 but for cold setting in. 



Considerable difficulty was anticipated in breeding the parasite 

 owing to its minuteness. The head and body length measures only 

 about one millimeter. A large box was prepared in which the breed- 

 ing was to be done. In actual practice, however, this box was found 

 to be of no value. When the tick was attached to its host, it was 

 necessary simply to allow a female parasite its freedom on the host. 

 It would search out the nymphs. When the nymph was free, it was 

 only necessary to put a glasis over the parasite and nymph to prevent 

 their escape. 



The table below shows the results obtained in the breeding exper- 

 iments: 



