PEDIGREE, 359 
hosts as well as carriers of disease-producing parasites. 
The gnats or mosquitoes (Culicide) 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 Axopheles 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 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, 
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 Fic. 189.—- Anurida 
metamorphosis appear much later (e.g. i date ga oe 
beetles in the Carboniferous ages); but it primitive wingless 
seems that the Palaeozoic insects were  Collembola. 
