FLEAS 69 



Frequently both adult and larval fleas are found pullulating in the 

 nests of hibernating mammals. Brumpt states that a certain Cerato- 

 phyllus found in the nests of hibernating voles, lays eggs and breeds 

 right through the winter. If this is true the host's long sleep must be 

 troubled by bad dreams. Certainly during the period in which the 

 hedgehog is torpid, its fleas are quite active. It has been shown how- 

 ever that the rhythmical inflation and deflation of the tracheal tubes — 

 in other words the flea's breathing — is considerably slowed up during 

 the hibernation of the host. The quickest rhythms are found in gravid 

 females in summertime and therefore it seems likely that this species at 

 any rate does not breed in winter. 



Bird fleas have a more sharply defined breeding season than mam- 

 mal fleas. Although in all species seasonal changes in climate affect the 

 number of eggs laid, the proportion which hatch and undergo meta- 

 morphosis, the duration of each larval stage and so forth, yet broadly 

 speaking, if conditions are reasonably favourable, rat fleas and many 

 other mammal fleas are known to lay eggs, even if reduced in number, 

 and breed all the year round. But the conditions such as plentiful blood 

 meals and a raised temperature which induce the common rat flea and 

 the stick-tight marsupial flea {Echidnophaga myrmecobii) to breed in mid- 

 winter in the laboratory, have no effect on the common hen flea which 

 will only lay eggs in the spring or early summer. This indicates that the 

 parasite is well adapted to its particular hosts. It is vital that the flea's 

 life-cycle coincides with that of birds, for it is only during a brief 

 period in the spring that the host occupies a nest. 



In India the native jungle fowl {Callus gallus) is not infested with 

 Ceratophyllus gallinae. This flea is undoubtedly a parasite of European 

 wild birds which has only fairly recently developed a marked pre- 

 dilection for the domestic fowl. Although birds are present all the year 

 round in hen houses Ceratophyllus gallinae still retains a definite spring 

 breeding season. In time this may be modified to suit the new condi- 

 tions. Here the stage is set for the evolution of a new physiological race 

 and possibly a new species. 



Some permanent parasites like the feather lice, pass their entire 

 life-cycle on their host. It is of supreme importance to them that their 

 eggs should not fall off' after they are laid. To ensure against this mis- 

 fortune the female glues them individually and with extreme eflficiency 

 to the feathers (Plate XXIV). In the case of the flea, which has a 

 free larval and pupal stage generally spent in the nest, the reverse is 



