FEATHER LICE I4I 



another, and the apparent resemblance they have among themselves, 

 scarce any power of the judgment can unravel and distinguish." 



Phylogeny of Host and Parasite 



The evolution of the birds, in comparison with many other groups 

 of animals, is believed to have been rapid. The earliest known bird — 

 or perhaps feathered reptile would be a better description- is represented 

 by a fossil {Archaeopteryx) from the Jurassic rocks some 120 million years 

 old; but by the Upper Eocene, some 60 million years later and between 

 40 and 70 million years ago, the fossil record shows that most of the 

 present orders and even families of birds were established. This relatively 

 rapid divergence and the fundamental changes which took place have 

 left few traces of the primitive arrangements of bones and muscles, 

 characters upon which relationships in the vertebrates are mainly 

 based. This, together with the paucity of the fossil record, due to the 

 fragile nature of the bones of birds, has left the student of bird evolution 

 largely groping in the dark. It would be of the utmost value, therefore, 

 if the present distribution and relationships of the Mallophaga could 

 throw some light on the phylogeny (or evolutionary relationships) of 

 their hosts, the birds. The course of evolution in the Mallophaga has 

 resulted in related bird hosts harbouring related Mallophaga. It has 

 been shown, for instance, that the head lice of all the waders are closely 

 related species of one genus. Can we make the reverse deduction and 

 affirm that the hosts must be related if the parasites are related, and 

 perhaps convince the ornithologist that relationships between the para- 

 sites can be a fruitful and reliable source of evidence for relationships 

 between the hosts ? 



The flamingoes (Phoenicopteridae) provide the classical example of 

 the usefulness of such deductions. In modern classifications, as we have 

 seen, these birds are usually placed with storks and herons (Ciconii- 

 formes), more rarely with swans, geese and ducks ( Anseriformes) . The 

 flamingoes are parasitised by species of three genera of feather lice 

 [Anatoecus^ Anaticola, and Trinoton) which are found elsewhere only on 

 the Anseriformes. The species parasitising the Ciconiiformes, on the 

 other hand, belong to different genera and are quite distinct from 

 any found on the flamingoes or the Anseriformes. The most likely 

 explanation of the presence of three duck-infesting genera on the 



