INSECTS AND HUMAN DISEASE 115 



also been called the " tiger mosquito," because its legs and 

 abdomen are striped with white, whilst in the upper 

 surface of the thorax there is a white lyre-shaped pattern. 

 Only the females imbibe human blood, and they feed both day 

 and night. The males have been accused of blood-sucking, 

 but this erroneous notion has probably arisen from the 

 fact that they settle on man for the purpose of imbibing 

 perspiration. Each female lays between twenty and 

 seventy-five eggs, and in this stage the insects are able 

 to tide over the winter when the weather is severe, for 

 their fertility is not destroyed by freezing. Under favour- 

 able conditions, however, the eggs hatch in from ten hours 

 to three days ; the larval period extends from six to eight 

 days, and the pupal stage may last less than two days, 

 so that the whole life-cycle may be completed in a little 

 over nine days, under favourable circumstances. We have 

 called the yellow fever mosquito a town insect ; it is more, 

 it is a domestic insect "as domestic as the flea, bug, 

 and cat." In its choice of breeding places, too, it haunts 

 man's dwellings ; it has been said that it never breeds in 

 any water with a natural earth bottom, but always in 

 artificial water containers, and not necessarily water con- 

 tainers by design, for the females will oviposit in a few 

 teaspoonfuls of water in the hollow base of an inverted 

 bottle (Plate VII.). And if the water evaporates and the 

 eggs are left high and dry, they will retain their vitality 

 for at least six months till more rain falls. 



Whether the opening of the Panama Canal will result 

 in the transport of yellow fever to Asia, time alone can 

 show. Stegomyia occurs in Asia in plenty, but so long as 

 the disease itself or infected mosquitoes are not carried 

 to Asiatic ports all will be well, for non-infective Stegomyia 

 is as harmless as the common British gnat. 



The common gnat, Gulex pipiens, of this country is an 

 annoying insect, though one of little economic importance. 

 Its near relative, Culex fatigans, however, is notorious 



