476 TRAKSACTIONS OP SECTION D. 



make this unlikely. The 'explanation' offered by Fruhstorfer, viz., that 'the 

 mimics Avere modified by the same (as yet unlcnown) influences under which the 

 colouring of the models developed,' is obviously no explanation at all. 



Since some of the forms resembled by the Eronias are known experimentally, 

 and otTiers are on good grounds believed to be more or less distasteful to 

 insectivorous animals, the theory of mimicry appears to be the most feasible 

 interpretation of the conditions obtaining in this genus. 



The likeness between Eronia leda and Tieracolus auxo is somewhat excep- 

 tional. The Eronia is cryptically coloured beneath; and the resemblance to 

 Teracolus, which is strongest in the male, may perhaps be really due to 

 affinity. 



6. The Relation of the Phylogeny of the Parasite to that of the Host. 

 By Launcelot Harrison, J3.Sc. 



The proposition I advance is : — That in the case of total obligate parasites, 

 closely related parasites will be found to occur upon phyletically connected 

 hosts, without regard to other cecologic conditions. As the state of evolution of 

 the parasite will be less advanced than that of the host, it follows as a corollary : 

 That a study of such parasitee may give valuable indications as to host phylogeny. 



(The following references may be consulted for more detailed statements : — 

 (1) Kellogg, American Naturalist, xlvii., p. 129; (2) ibid., xlviii., p. 257; 

 (3) S. J. Johnston, EejJt. Aust. Ass7i., 1913; and (4) Ecpt. Brit. Assn., 1914; 

 (5) Harrison, Aust. Zoologist, 1914, p. 7; and (6) Parasitology, viii., p. 88.) 



The evidence I shall bring to support the above statements is derived from a 

 study of conditions in the Mallophaga. Kellogg (1) has made a similar state- 

 ment based on a study of the same group. He has also (2) extended his studies 

 to the Anoplura, and finds that his thesis holds for this order. A striking illus- 

 tration is the occurrence upon man, upon species of the family Simiidee, and of 

 the genus Ateles alone among the Cebidee, of the Anopluran genus Pediculus; 

 while the closely related genus Pedioinus occurs upon the lower Quadrumana. 



Johnston (3) has compared the trematode fauna of the frogs of Europe, Asia, 

 America, and Australia, and finds a common occurrence of species of Pneu- 

 monoeces in the lungs, Pleurogenes in the intestine, Di'plodiscus in the rectum, 

 and Gorgodera in the bladder. He finds flukes from Dusyurus and Ornithorhyn- 

 chus intermediate between the Fasciolirue of higher mammals and the Psilosto- 

 minse of the Sauropsida. He also finds (4) that species of Linstowia (Cestoda) 

 and Harmostomum (Trematoda) from Australian marsupials have their nearest 

 relatives among species of the same genera from American marsupials. The 

 parasitic Platodes, though not total obligate parasites in the same sense as the 

 Mallophaga, show the same relation to their hosts. 



I find that, in general, the Mallophaga parasitic on any avian order are 

 recognisable at sight. In many cases, especially in certain genera, it is possible 

 to state definitely that a parasite has come from a particular family of birds. 

 Many species have a world-wide distribution, but always on closely related birds. 

 Thus Philopterus km occurs upon all gulls ; Llpeurus anatis upon all ducks ; 

 L. columbce upon all pigeons; Colpocephalum flavescens upon all hawks. The 

 genus Q^etrophthalmus has adopted a epecialised habitat in the gular pouch of 

 pelicans, and has its tracheal system specially modified in accordance with the 

 changed conditions. iSpecies of Tetrophthalvius occur on all pelicans, in the 

 same situation, and are all similarly modified. The only reasonable explanation 

 is that the parasites have had common origin. 



Owing to equable conditions of nourishment and temperature, the Mallophaga 

 have had no stimulus to evolve as rapidly as their hosts. This is abundantly 

 proved by the fact that parasites fjom the various genera of a bird family are 

 often hardly specifically distinct. The Philopterus of Cuculus canorus is with 

 difliculty separable from those found upon the Australian genera Cacomantis and 

 Chalcococcyz. 



Bird phylogeny has always presented a difficult problem. The biological 

 condition of the Mallophaga indicates that they can afford valuable evidence as 



