Ixodidae 253 



lowed in feeding nymphs is similar to that for feeding larvae. One of 

 the i 3 //' x 4" cylinders is opened and, with the help of an assistant, the 

 contents are equally distributed among 6 animals in infesting bags. 

 Considerable experience and dexterity is required in completing the 

 process without the escape of ticks. The rabbits are then treated as 

 in larval feeding. Engorgement is accomplished in about 8 days and 

 the tick picker is also used in collecting the fed ticks. The contents 

 of the cage bags are shaken in the hopper and a stream of water from a 

 hose is directed onto the canvas bottom of the bag to wash the remain- 

 ing ticks and detritus into the picker. The soluble wastes are washed 

 through while the ticks and non-soluble waste of the same size are 

 retained on screen B. The coarse material is retained by screen A. 

 Cup C is not used while the bags are being cleaned. After all the bags 

 are cleaned, water is directed into the picker and the material in it 

 thoroughly washed. Screen A is removed and its retained material 

 discarded. Screen B is set on edge and the material on it washed down 

 into the cup which is now in place. The cup is removed and the con- 

 tents are slowly centrifuged in a screen container to remove the excess 

 water. This is accomplished in a converted cream separator. Drying is 

 then completed by placing the material in a current of warm air sup- 

 plied by an electric hair dryer. Final cleaning is accomplished by 

 sorting the remaining debris from the ticks, after which the latter are 

 counted by measuring their volume in cubic centimeters, 35 ticks being 

 the equivalent of 1 cc. An average of about 400 ticks per animal is 

 ordinarily obtained. The nymphs are placed in cardboard pill boxes, 

 2" in diameter and %" in depth, about 200 per box, and the lot number, 

 date and other necessary data stamped on the covers. 



Molting of nymphs occurs within a rather wide range of temperature 

 and humidity. Ordinarily nymphs are held at 22 C. and relative hu- 

 midity of 40-80%. Under these conditions molting takes place in 

 about 2 1 days. Transformation to the adult stage is accelerated by a 

 low relative humidity, while a high humidity tends to retard the process. 



STORAGE OF TICKS 



In the course of routine or experimental rearing, situations occasionally 

 arise when it becomes necessary to delay development or postpone the 

 feeding of ticks. The conditions required for minimum mortality dur- 

 ing storage are dependent on the stage of tick being dealt with, the 

 principal factors being its ability to withstand desiccation and starvation. 

 Adult ticks are better able to survive long periods of fasting than the 

 immature stages, the nymphs being more resistant than larvae. None of 

 the stages are markedly resistant to desiccation. 



Adults. Unfed adults of D. andersoni collected in nature or recently 



