248 Phylum Arthropoda 



Adjacent to the rearing room there is a workers' street clothes locker 

 room, a shower room, a "deticking" room containing an electrically 

 heated cabinet and a 3 panel full length mirror, and a work clothes locker 

 room. Coming on duty the workers leave their street clothing in lockers 

 in the first room and don one piece white coveralls in the fourth. On 

 leaving at the close of work, the coveralls are placed in the heated cabinet 

 in which the temperature is maintained between 50 C. and 65 C. for an 

 hour or longer to kill any ticks that may be on the garments. The workers 

 then examine their bodies for ticks before the mirror and take a shower 

 bath before dressing for the street. 



REARING PROCEDURE 



Although D. andersoni can be reared through many successive genera- 

 tions under laboratory conditions, stock thus carried on seems gradually 

 to lose its virility. It has been found best, therefore, to start each rear- 

 ing year's stock from new adult ticks collected from nature. The succes- 

 sive steps involved in rearing this stock through a generation are as 

 follows: (1) collection of adult ticks from nature, (2) engorging of fe- 

 males, (3) oviposition and hatching of eggs, (4) engorging of larvae, 

 (5) engorging of nymphs, and (6) storage of the various stages. Most 

 of the essential equipment is shown in text figures. In order to have 

 1,000,000 adults of the reared generation, it is necessary to collect or 

 engorge approximately 5,000 females, requiring about 170 rabbits. 

 These females will deposit 20,000,000 eggs yielding approximately this 

 number of larvae. About 700 rabbits are required to feed these larvae, 

 using about 30,000 larvae per host. Approximately 4,000,000 engorged 

 larvae are obtained. These will yield about the same number of nymphs. 

 Nymphal feeding requires about 2,800 rabbits using about 1,200 ticks 

 per host. The approximately 1,000,000 engorged nymphs produced yield 

 an almost equivalent number of adult ticks. Thus only about % of 

 the larvae are brought to maturity, the principal losses being incurred in 

 the feeding of the larvae and nymphs. This results in part from the 

 fact that all the ticks of a given lot are not ready to feed at the same 

 time. 



D. andersoni is not markedly host specific and all stages feed readily 

 on domestic rabbits. In the routine feeding of D. andersoni for mass 

 rearing only rabbits are used. In order that there may be as little 

 moisture and waste food material as possible in the rearing cage bags 

 to be later described, a scanty diet consisting solely of carrots is em- 

 ployed. The larvae and nymphs will feed on almost any small mammal 

 and adults can be fed on any of the larger domestic animals and even on 

 guinea pigs. 



Collection of Adult Ticks. To obtain a rearing stock of D. andersoni 



