133 



of fly from generation to generation exceeds mortality, while dispersal 

 into surrounding unfavourable zones results in mortality exceeding 

 natural increase, and thus a natural balance is maintained so long 

 as flies are free to disperse from the infested centres to surroundmg 

 zones. If dispersion is interfered with, this balance is upset, but 

 this very rarely happens in nature. 



The inimical factors in the bionomics of G. palpalis are discussed. 

 It is considered wholly impractical to attempt any control measure 

 involving artificial destruction of the flies, and wholly necessary 

 to rely upon measures designed to deprive them of either food or 

 protection or to render food less available to them. The clearmg 

 measures already in use have proved efficacious on many occasions. 

 The maximum of economy and efficiency is to be gained through 

 clearing at the centres of infestation, where natural increase is most 

 rapid, for by clearing these the dispersal of flies into the surrounding 

 zone is prevented and the effect is general. In discussing the degree 

 of density that mav be considered obnoxious, the beUef is expressed 

 that a density, as measured by the males to be caught per boy per hour, 

 of 6-0 is normallv safe and sanitary, but that one of 15-0 or 20-0 would 

 ordinarily be dangerous. The expense of reducing density to 

 everywhere would be too great to be considered. 



NuTTALL (G. H. F.). On Coloration in Ticks, W.—Parasitologij, 

 Cambridge, xii, no. 1, January 1920, pp. 1--6, 2 plates. 



The ticks dealt with include Amhlijomma Jiebraeum, A. gemma, 

 Dermacentor venustus, D. variabilis and D. reticidatus niveus, the 

 coloration of which, as seen in living examples, is depicted for the first 

 time. The colour-producing layer may be removed by the use of 

 caustic potash. 



Attention is drawn to the desirabihty of recording the colours of 

 ornate ticks when alive. 



NuTTALL (G. H. F.). Regeneration of the Mouthparts and Legs in 

 Ticks. Argas j^ersicus, Amblyomma hebraeum and Hijalomma 

 aegypticum. — Parasitology, Cambridge, xii, no. 1, January 1920, 

 j)p. 7-26, 6 figs. 



The contents of this paper are indicated by the title. 



NuTTALL (G. H. F.). On Fahrenholz's purported New Species, 

 Sub-Species and Varieties of Pediculus. A Criticism of Methods 

 employed in describing Anoplura. — Parasitology, Cambridge, 

 xii, no. 2, March 1920, pp. 136-153, 2 charts. 



Attention is drawn to certain grave sources of error underlying the 

 present mode of differentiating Anophu'a and more especially species 

 of the sub- order Siphunculata. This paper is divided into three parts 

 deahng with Fahrenholz's descriptions of supposedly new species, etc., 

 the authors detailed criticism thereon, and his conclusions therefrom 

 in respect of the synonymy of Pediculus humanus. 



