PEDIGREE. 



359 



hosts as well as carriers of disease-producing parasites. 

 The gnats or mosquitoes (Culicidae) are perhaps the most 

 important in this respect. Human malaria is conveyed by 

 at least twelve different species of mosquito, of which those 

 belonging to the genus Anopheles have the widest dis- 

 tribution. Anopheles maculipennis occurs all over Europe, 

 in many parts of Africa, North America, and India, 

 and in all these countries it carries malaria (see Fig. 182). 

 Proteosoma, the malaria parasite of birds, is carried by a 

 CuleX) a related genus. The unknown parasite of yellow 

 fever is transmitted by the bite of another mosquito, 

 Stegomyia fasdata. 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, 

 Glossina palpalis (Fig. 53) and G. morsitans, convey the 

 parasites (Trypanosomes) of sleeping sickness and 

 Nagana respectively. The latter disease, which is com- 

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

 domesticated animals, is probably also 

 conveyed by other species of Tsetse 

 flies. In general, one may say that 

 wild animals, Which appear to be un- 

 affected by the parasites which they 

 contain, are the source of the fatal 

 infection of new-comers. 



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 FIG. 

 metamorphosis appear much later ' (e.g. f m ^^* e of the 

 beetles in the Carboniferous ages); but it primitive wingless 

 seems that the Palaeozoic insects were Collembola. 



