CHAPTER XXX 



MALLOPHAGA AND ANOPLURA (LICE) 



General remarks — Mallophaga — Anoplura — Pediculidse — Pediculinse — 

 Haematopinidse- — References . 



GENERAL REMARKS 



The wingless insects which occur as ectoparasites on mammals 

 belong as a rule to the Mallophaga and the Anoplura, when they are 

 generally called ' lice,' or to the Siphonaptera, when they are 

 called fleas, while some few belong to thePupipara. 



The Mallophaga (biting lice) and Anoplura (sucking lice), however, 

 differ from the Siphonaptera (fleas), in that in the former the whole 

 of the life-history is spent upon the vertebrate host, while in the 

 latter the larvae live in soil or in protected areas in houses. More- 

 over, the fleas can change from one host species to another, while the 

 lice have an extraordinary limitation, as they may spend genera- 

 tions on individual hosts, and generally only change from one host 

 to another of the same species by actual contact, and as a rule die 

 in a few days if separated from a host or if a host dies. 



This limitation to one given species of host has been ably 

 demonstrated by Kellogg, who has pointed out that it explains 

 many of the curious features of their evolution. 



Kellogg and Mjoberg believe that the Mallophaga and the Anoplura are 

 fairly closely related to one another. They think that it is possible that the 

 Mallophaga are the more primitive, especially as no Anoplura are known on 

 marsupials, while Mallophaga are present, which they think points to the 

 possibility of these mammals being older than the sucking lice, especially as 

 the known genera of two-clawed Mallophaga found on mammals are limited 

 to marsupials, while the two-clawed condition is common to the Hexapoda 

 generally, while all the Anoplura found on mammals are one-clawed. 



It is possible that the ancestors of the Mallophaga may have been related 

 to the ancestors of the book louse {Atropos divinatoria) , which belongs to the 

 Psocidae, a family of the Neuroptera, there being perhaps a common psocid- 

 mallophagan ancestor, from which, by process of evolution, the Psocidae and 

 the Mallophaga, and later the Anoplura, were evolved. The difference in the 

 mouth parts of the Mallophaga and Anoplura is looked upon as being adoptive 

 rather than palegenetic in character. 



The relationship of the Psocidae to the Mallophaga lies in the common 

 external and internal characters, as well as in their habits, and more especially 

 in a very curious pharyngeal sclerite, which is thought to be a modified hypo- 

 pharynx, which is found in both these groups and nowhere else in the 

 Hexapoda. 



Once started on their evolution, the Mallophaga have been influenced 

 mainly by the fact that they live in a sort of ' island isolation ' on given 



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