Absolute Humidity as a Factor in Insect Cold Hardiness with a Note on the Effect of Nutrition on Cold Hardiness

In both eggs and larvæ of Hemerocampa lencostigma Smith and Abbot, cold hardiness can be expressed by the equation T1 = K1/Ha where T1 = survival temperature in degrees centigrade (or cold hardiness to the intensity factor). Ha = absolute humidity in millimeters of vapor pressure. K0 = constant for eggs = 44 K1 = constant for 1st instar larvæ = 41.8 K2 = constant for 2nd instar larvæ = 37.4 K3 = constant for 3rd instar larvæ = 34 Larvæ from cold hardy eggs tend to be more cold hardy than larvæ from non-cold hardy eggs. Larvæ of each succeeding stadium tend to be less cold hardy than the one preceding.