3 46 PH\ 7 L UM AR THRO POD A. 



fever is transmitted by the bite of another mosquito, 

 Stegomyia fasciata. It occurs in all parts of the world 

 between the parallels 40 N. and S. " It is a most vicious 

 biter both by day and night, and breeds in small artificial 

 collections of water, such as barrels, puddles, cisterns, and 

 even in such small receptacles as sardine tins " (Theobald). 

 Culex fatigans and C. pipiens act as carriers of Filaria 

 bancrofti or F. sanguinis hominis nocturna, the parasite of 

 the human disease, filariasis. The African Tsetse flies, Glos- 

 sina palpalis (Fig. 51) and G. morsitans, convey the para- 

 sites (Trypanosomes) of sleeping sickness and Nagana 

 respectively. The latter disease, which is communicable 

 to horses, cattle, goats, sheep, and other domesticated 

 animals, is probably also conveyed by other species of 

 Tsetse flies. Wild game appear to be unaffected by the 

 parasite, but are probably the source of fresh infections in 

 new districts (see p. 117). 



PEDIGREE. 



Insects must have appeared relatively early, for remains 

 of a cockroach-like form have been found even in Silurian 

 strata. The higher forms with complete metamorphosis 

 appear much later (e.g. beetles in the Carboniferous ages) ; 

 but it seems that the Palaeozoic insects were mostly 

 generalised types, prophetic of, rather than referable to 

 the modern orders. 



As to the pedigree of insects, the wingless Collembola 

 and Thysanura are doubtless primitive. They lead us back 

 to some of the less specialised Myrio-pods (e.g. Scolopen- 

 drella), back further to Peripatus> which helps to link the 

 Tracheate to the Annelid series. 



But though the primitive wingless insects, the simple 

 types of Myriopods, and Peripatus, represent ascending steps 

 in evolution, what the actual path has been we do not know. 



