350 GEORGE H. F. ISTUTTALL. 



to protrude the latter may be periodically moistened (if needed) with a drop of water„ 

 Note when the first eggs were laid and when the first larvae emerge. Preserve some of 

 the larvae in alcohol. 



A week or more after larvae have emerged place them upon some small animal 

 which is available and capable of supporting captivity. Hedgehogs {Erinaceus 

 europaeus) have been found by us to be very suitable for raising many ticks infesting 

 mammals in Europe and Africa, because the bristles on the animal prevent its- 

 scratching off the ticks. The host (dog, guinea-pig, etc.) should be placed in a metal 

 cage which can readily be subjected to daily inspection and which is provided with 

 a coarse net- work floor through which gorged ticks may drop into a tray underneath. 

 Sheets of white paper, laid upon the tray every day, greatly facilitate the finding o£ 

 small gorged ticks (larvae) which may drop from the host. The whole cage should 

 be placed in a white-painted tray surrounded with a gutter containing water which 

 effectually prevents the escape of ticks. Inspect the tray daily and note when the 

 first gorged larvae are collected. The larvae are readily picked up by means of a fine: 

 camel's hair brush and they should be transferred to corked tubes similar to those 

 in which the eggs were kept. Count the number of gorged larvae which are collected 

 daily and enter the numbers upon the records. Having noted w^hen they dropped 

 from the host, the next thing to record is the date of their emergence as nymphs. 

 The nymphs will require a week or more before they are ready to feed upon a host. 

 The process described for the larvae is repeated by the nymph and finally the adult 

 stage is attained. 



The adults, and for that matter the larvae and nymphs in some cases, can also be 

 conveniently raised upon larger animals if these are available. The unfed ticks are 

 then placed in strong white linen bags which can be tied about the ears (cattle and 

 horses) or scrotum (ram, goat, bull). The bags should be then periodically inspected 

 and the gorged ticks removed. 



The length of time occupied in metamorphosis from egg to larva, larva to nymph 

 and nymph to adult is much influenced by temperature, consequently a daily record 

 should be kept of the temperature at which the ticks are maintained when undergoing 

 the change. The behaviour of the sexes upon the host should be noted, as well as 

 the proportionate numbers of each sex which emerges from a given number of nymphs. 

 The number of eggs laid by each female may be estimated with considerable accuracy 

 by suspending the eggs in water and spreading them out in a uniform layer within a 

 square frame made of strips of glass fixed upon a sheet of glass of suitable size. Count 

 the eggs in a row on two sides of the square and multiply these numbers to obtain the 

 total number of eggs. 



Although these directions suggest that the raising of ticks under experimental 

 conditions is a simple matter, this is frequently not the case in practice. Some ticks 

 have not been raised by us, though repeated attempts have been made under various 

 conditions, and others have been repeatedly raised through several generations without 

 any particular difficulty. We do not know the cause of our failures in some cases, 

 whereas in others we have traced it to unsuitable conditions of moisture and tempera- 

 ture. Some ticks must be kept dry, others in a slightly moistened atmosphere, others 

 again in a saturated atmosphere during metamorphosis. Moulds are a fruitful source 



