136 FLEAS, FLUKES AND CUCKOOS 



cuckoos of the British Isles would have no particular species of lice, but 

 they would be parasitised by a variety of passerine-infesting species. 

 This however is not the case. The adult cuckoo in England is infested 

 by three species of lice belonging to the genera Cuculoecus, Cuculicola and 

 Cuculiphilus , which, as their names imply, are true cuckoo-infesting 

 genera found on species of the cuckoo family throughout the world, 

 but not on the Passeres. Thus, although the lice of the passerine 

 foster parents have ideal conditions for transference — continuous 

 contact and no competition — the host specificity already developed 

 makes establishment on the new host impossible. There is no satis- 

 factory explanation of how the cuckoo acquires its normal lice. In 

 most birds the lice can pass from the parent to the young in the nest, 

 but in the case of the cuckoo contact between individuals takes place 

 only during mating, and it must be presumed that the lice are usually 

 transferred at this time. Transport by louse-flies (further discussed 

 below) in the cuckoo's winter quarters may be another method by which 

 lice are passed from adult to young birds. 



For dispersal and survival the lice must pass from individual to 

 individual of the same species of bird host. This may take place 

 during mating, brooding of the young, roosting of gregarious species 

 and by the use of common dust baths. On the death of the bird 

 the lice are doomed to extinction unless they can transfer them- 

 selves quickly to another individual, for the lice soon become torpid 

 without the warmth of their host. As the bird begins to cool the 

 lice come to the surface of the feathers and will leave them for any 

 warm or rough- textured object. This desire to leave the dead and 

 now unattractive body of their late host probably accounts for the 

 many recorded cases of "phoresy" (see p. 18) among the Mallophaga. 

 Chewing lice have frequently been found attached to louse flies (tail- 

 piece p. 157) and have also been recorded once on a flea, three 

 times on mosquitoes, once on a Haematobia (a blood-sucking fly), a 

 dragon-fly, a bumble bee and a butterfly — this last record by Kirby and 

 Spence (1826) seems to be the earliest mention of phoresy in the Mallo- 

 phaga. In the first four cases, the lice had attached themselves to 

 another parasite off the same host; in the last three, the louse had 

 probably boarded the insect when it had alighted for a few minutes on 

 the corpse. An interesting case of phoresy was observed in the Shetland 

 Isles one summer, where most of the starlings were found to be infested 

 by feather lice and louse flies. One starling examined immediately 



