10 American Midland Naturalist Monograph No. 1 



essential conditions for keeping the ticks alive for prolonged periods are (a) 

 containers that permit the maintenance of a higher humidity than is usual in 

 room atmosphere, (b) sufficient air, and (c) avoidance of over-heating. The 

 container should be such as to facilitate frequent examinations of the speci- 

 mens. We have used two methods successfully. 



For one method we employ desiccator jars that provide a space for contain- 

 ing a fluid below and for holding vials of ticks above. A "floor" for the upper 

 space can be made of cardboard saturated with melted paraffin. Pill boxes 

 containing ticks direct from the field may be placed temporarily in the upper 

 chamber. A relative humidity of 92 percent is maintained 'by a saturated 

 solution of ammonium chloride (NH 4 CI) in the lower chamber.- Paper 

 pill boxes become moist and soft if held in the desiccator jars very long. 

 On the other hand, ticks in glass vials with cotton plugs may be held indefinite- 

 ly. The jars are kept at room temperature and out of the sunlight. Mold some- 

 times develops but causes very little difficulty if the ticks are held in glass vials 

 and can be further prevented or reduced by using only sterile vials. 



Various modifications of the "Hixson jar" are also useful. We have found 

 the modification described below to be of value in holding a few living ticks in 

 the laboratory and also in collecting critical material in the field. Hixson (1932) 

 described and figured a small % inch cork-stoppered shell vial "jar" with wet 

 sand in the bottom. The tick or ticks are placed in a l /^ inch tube plugged with 

 cellu-cotton at both ends. The latter is held in a fixed position in the jar by 

 inserting one end in a central hole through the stopper. 



For our purposes we have modified the "jar" by using a wide-mouthed 

 bottle, 2 inches in diameter by 4 inches tall, with plaster of paris in place of 

 the sand. The plaster of paris is allowed to set in the bottom of the bottle. The 

 jar is then placed in a warming oven with the mouth open until the plaster is 

 thoroughly dry. Six to ten drops of water are added to the plaster to maintain 

 a moderate degree of humidity. The inside tube should have a diameter of 

 about 1 /g of an inch, should be clean and sterile and should not reach the 

 plaster of paris. 



Critical living specimens may be placed singly in the inner glass tubes and 

 when ecdysis occurs the molted skin is available. The latter is often of special 

 value 'because the hypostome or other parts are available for comparison with 

 the same parts in the subsequent stage. The cast skin of the hypostome may 

 be placed in absolute alcohol, then transferred to xylol and when mounted in 

 balsam is nearly as useful as the actual tick of the stage concerned. These small 

 jars have several advantages when it is desirable to keep living ticks and make 

 daily observations and records of their development. They are also used in the 

 field when especially interesting lots of ticks are collected and when shipped 

 they are put in double mailing tubes. 



2 See International Critical Tables, vol. I. p. 67. for information on maintaining 

 constant humidities. 



