78 
Biologfi of Ixodidae 
differences in size from a batch of about 100 belongiug to one family. 
The smallest larva measured 0'53, the largest 0'60 mm. in length, the 
variation being as 88 :100. 
Changes in colouration at death. 
On dying, the ticks usually turn blue-green all over, the bluish 
annulations on the legs becoming very dark. At first, the limbs assume 
the same bluish tint exhibited by the palps in living adults, the limbs 
then gradually darken and the colour spreads all over the body. It 
would be interesting to determine the cause of this change in colour. 
In Neumann’s description of 1. putus this blue-green colour is referred 
to as if it were natural; this is, however, not the case. To my knowledge, 
no similar change of colour occurs in other ticks when they die. 
Feeding experiments. 
Males. All attempts to make the males feed upon a host (duck, 
sea-gull, fowl) failed utterly. About 15 males of various ages were 
repeatedly tried on a fowl and 12 males on a gull and duck. 
Females. Out of 15 unfed females which were placed upon a fowl, 
five attached themselves to the host after some patient waiting; all of 
them died in situ after about three days and, soon after they died, they 
assumed an olive-green colour similar to that of ticks which die unfed. 
The dead ticks rapidly grew dry and brittle and remained in this 
condition attached to the host and gradually fell to pieces. 
I next tried the ticks upon a duck as being probably a more 
favourable host. About 25 females promptly attached themselves when 
placed upon the bare skin beneath the bird’s wing, but all of them were 
dead and brittle by the fifth day, including a female which had become 
partially gorged. Thinking that the death of the ticks might be due 
to the dry heat in proximity to the bird’s body, I bathed the bird 
periodically in sea-water to simulate the conditions of the marine birds 
(guillemots, ducks, gulls, etc.) upon which the tick is found in nature, 
but the results were negative both when fertilized and unfertilized ticks 
were used. Although 13 females were placed upon a young gull {Larus 
ridihundus), none of them survived upon the host. Females were also 
tried upon a canary, but with negative results. Curiously enough, 
a single female which somehow had managed to escape, attached itself 
