| Abstract: | Mortality of adult Tingis ampliata H.-S. increases with decreasing temperatures from ?2 to ?13° in the laboratory. There is no differential susceptibility of the sexes to low temperatures in the above range, but a higher proportion (5%) of females tolerated longer periods of exposure to these temperatures than males. There is a great deal of individual variation in cold hardiness of bugs of both sexes. Seasonal variation in cold hardiness is associated with variations in mean air temperatures during winter. Cold hardiness increases from October to December and then decreases progressively afterwards till the following April. During the coldest month (December), undercooling point ranged from ?22.0 to ?31.5° for females and ?22.2 to ?31.4° for males. Presence of food in the gut and contact with wet organic substrate such as dead Holcus leaf, both reduce cold hardiness of bugs by about 5° compared with unfed bugs or those tested on dry, dead or living green Holcus leaf. The difference between cold hardiness of control and fed bugs is more marked in individuals that have access to food for 48 hours than in those that have access for only 24 hours. |
