Eggs of snow-melt Aedes undergo changes in their response to a hatching stimulus. These changes are related to species, prior thermal history, and age of egg. Based on definite hatching responses, eggs may go through 5 hatching states including (1) no response regardless of temperature and stimulation; (2) response to a hatching stimulus which is dependent on hatching temperature; (3) response to at hatching stimulus which is independent of hatching temperature; (4) hatching upon contact with water which is dependent on the hatching temperature and (5) hatching upon contact with the water independent of hatching stimulus and temperature.