Insects and Parasitic Diseases. 95 



Swingle (1912, p. 22) found that '* ticks " kept in boxes covered 

 ■with gauze all died in i'our days, whether they were kept warm 

 -or cold. Young *' ticks," before taking a meal were kept a little 

 .longer, and in one case he was able to keep one alive for seven days. 

 Sweet and Seddon (1917, p. 13), kept ''ticks" alive off the host 

 for periods of eleven and eleven and three-quarter days on soil in a 

 «cellar. 



In one experiment the present writer kept an adult '' tick " in a 

 cellar alive for eighteen days. In thre.e experiments under similar 

 -conditions to the above, two '* ticks," one under twelve hours old 

 -and unfed, the other about seven days old, lived for fourteen days. 

 In two other experiments a young unfed " tick " and an adult 

 *** tick " lived for thirteen days. In the latter case the insect was 

 kept under conditions closely simulating natural surroundings. 

 In yet anotlier experiment a female *' tick " which was kept off the 

 ^host under conditions sucli as njight be found on any sheep i-un sur- 

 vived to the eleventh day. 



Curtice (1890, p. 40) remarks of the '' sheep-tick " : *' It is not 

 at all probable that they can exist many days apart from the sheep 

 -as they are unfitted by structure for any other habitat." Herms 

 ^(1915, p. 294), referring to this insect, says : " When off the sheep 

 the insects die in fi-orn two to eight days, most of them dying in 

 rabout four days." 



Swingle (1913, p. 22) goes further, and remarks: "The 'sheep- 

 lick ' spends its whole life on the sheep. It is a false idea that 

 Ihe ' tick ' may drop off the sheep, and live for a long tinie in the 

 grass or brush, and l-e picked up again by sheep sometime later, as 

 is the case with tlie true tick." Doubtless these statements might 

 be applied in most cases to Australia also, but since it has been 

 •shown by Sweet and Seddon and by the present writer that " ticks " 

 remain viable for a longer period off the host than appears to be the 

 'Case in Arn.erica and Europe, and in view of the well-known habit 

 of these insects in crawling over the sui'face of the fleece in warm 

 weatlier, it would appear very probable that some of them do become 

 dislodged from the host and ultimately find their way back to the 

 ■i^heep. It must be observed, however, that in most cases "ticks" 

 apart from the host do not die rapidly, but weaken gradually until 

 i:hey are no longer able to attach themselves to any object. There 

 is a period, therefore, in the life of such *' ticks " during which 

 the individual, owing to physical weakness, would probably not be 

 able to avail itself of an opportunity of continuing its existence on 

 •tlie host. 



