Some Habits and Hosts of Bird Ceratophylli. 77 



examining material from nests, one finds fleas feigning death with the legs 

 tightly tucked up to the body, in which condition they resemble little 

 shining seeds. 



Thrice when a swarm was encountered, I found that no attention was 

 paid to my hand till it had approached within, say, a couple of inches of 

 the vanguard. Then an excited jumping ensued so straight up and down, that, 

 at the time, the conviction was irresistible that the fleas were aware of the 

 proximity of food. Later the point became more doubtful when examples 

 oi farreni could not be induced to leap towards a warm object held above 

 them. It is more than likely that, in a life so precarious as a flea's, 

 speculative jumping plays a very large part. It is only fair to add, however, 

 that smell may guide Ceratophylli to their hosts. I have not tried to 

 ascertain if this is so, indeed it does not seem easy to devise a decisive 

 experiment. 



Presumably all these bird fleas will attack man on occasion, and I am 

 personally satisfied that gallince and farreni (and sciurorvm) do so. But 

 it is by no means certain that they will always bite even when they have 

 the chance. Newly emerged imagines have much fat in their tissues — 

 especially round the alimentary canal — which must form a reserve of food 

 for some time. I have not been attacked by bird fleas in this condition. 

 Probably their attention is otherwise engaged. 



Breeding. — Possibly my experience may be unusual in this respect, but 

 until December 1909 few cases of $ and $ in coitH had come under 

 observation. In examining then a Martin's nest {Ghelidon urbica) I put 

 the fleas (C. farreni) into a glass-topped box as they were taken. As nothing 

 happened the box was laid aside, but shortly afterwards a £ and a ? were 

 seen to have copulated. In this state they remained about half an hour, 

 which subsequent observation showed to be fairly normal, though sometimes 

 (with a low temperature) an hour to an hour-aud-a-half elapsed before 

 separation. Of twenty fleas put into a test tube on the same day three 

 pairs shortly mated, but, at the time, no details were made out owing to the 

 creatures confused and rapid movements. 



Next morning about a dozen farreni, newly emerged from pupre, were 

 segregated in a test tube and the mouth plugged with cotton wool. In half 

 an hour no unions had occurred. This was so contrary to expectation as 

 to cause a comparison of the conditions of the two experiments. The only 

 difference seemed to be this, that on the previous day the weather had 

 been appreciably warmer, besides which both box and tube had been held 

 sometime in hand, while this morning the temperature was hardly above 

 freezing point. Accordingly I placed the test tube in the palm of my hand. 



