The Stegomyia is preëminently a house mosquito and a town mosquito. It is the domesticated one, while the malaria-transmitting ones are rural and feed in natural plant-containing bodies of water instead of the water in old tin cans, roof gutters, cisterns or other utensils surrounding the house which are preferred by the yellow fever mosquitoes.
Stegomyia seem to prefer water for breeding that is slightly tainted with sewage, although developing equally well in fresh water. They will also develop in brackish water.
When once this mosquito takes up its residence in a certain room of a house it rarely leaves it and thus is explained the danger of occupying a room which has been occupied by a yellow fever patient. Then too, the warning sound, so characteristic of the approach of most mosquitoes, is not given by Stegomyia.
The female lays about 70 eggs in small groups and not in a compact egg raft as with Culex. The eggs are therefore difficult of detection. The eggs do not suffer after rather prolonged drying. Even temperatures approximately 0°C. do not seem to destroy the viability. It would seem probable that it is this stage in the metamorphosis of Stegomyia which is responsible for the survival of the species under unfavorable conditions.
The eggs the American Commission received from Finley had been deposited thirty days previously on the edge of some water in a basin. The water had meanwhile evaporated and the eggs were dry. Notwithstanding this the eggs promptly hatched out when water was poured in the basin.
The most favorable temperatures for these mosquitoes range from 29° to 31°C. Under 20°C. the eggs do not hatch out.
The larvae, which hatch out in about two days, develop into pupae in approximately one week. In about two days the fully developed insect breaks out of the pupal case. It will thus be seen that a period of ten to fourteen days suffices for a generation. The insect is almost black and has a silvery lyre or Jew’s harp pattern marking on the thorax. The legs and abdomen also have silvery bands. The female lays several batches of eggs and has been observed in one instance to live 154 days. The French Commission kept a female alive 106 days. They consider that life under normal conditions is much shorter in duration than in captivity. If deprived of water the adult insect only lives about five days. In a refrigerator, Guiteras was able to keep mosquitoes alive, without food or water, for eighty-seven days.
On fruit and sugar vessels the conditions for the development of Stegomyia are exceptionally favorable.
These mosquitoes are prone to remain in the same house where they have been feeding. Carter has pointed out that yellow fever rarely spreads more than 75 yards from an infected house so that it is improbable that infected mosquitoes fly, or are carried by the wind, any great distance.