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. The same authority has also noted that ships in Havana harbor lying about 400 yards from shore never become infected when the crew have not been ashore or where infected ships have not been anchored near by. It is probable that they are carried aboard ships in connection with coaling or provisioning rather than blown aboard by prevailing winds. [Illustration: FIG. 45.—Temperature chart of Yellow Fever. A, Mild case with recovery. B, Severe case showing the saddle-back temperature curve similar to that of dengue. C, Chart of fatal case of yellow fever.] PATHOLOGY AND MORBID ANATOMY