The Biology Of Culex Nigripalpus Theobald (Diptera: Culicidae)1 Part 2. Adult Characteristics at Emergence and Adult Survival without Nourishment

Abstract

Adults of Culex Nigripalpus Theobald were analyzed for size, dry weights and energy reserves at emergence. The specimens were obtained from larvae reared under 4 different environmental conditions—quantity of food, density of larvae per pan, salinity of the medium and temperature. Maximum expression of these characteristics was observed in adults at emergence, when larvae were reared on 2× basic ration in tap water at 27°C, with either 75 or 200 larvae per pan. Wing length, wing breadth and hind femur length were affected more by temperature than by quantity of food, whereas thorax length, dry weights and amounts of energy reserves were mainly controlled by the quantity of food. The adult survival patterns observed with 3 different groups, in which the adults have almost the same size but different amounts of energy reserves, showed the innate survival pattern, which is probably characteristic of C. nigripalpus. The 50% survival points in both ♂♂ and ♀♀ were found to be dependent on the amount of percent lipid at emergence. The percent glycogen does not affect 50% survival points. The loss in dry weight at 50% survival points was found to be about 35% of the dry weight observed at emergence, whereas percent lipid and percent glycogen were reduced by 80–90% of the amounts at emergence. Trehalose concentrations increase significantly immediately after emergence, sometimes reaching up to 300% within 12 hours after emergence. This high level of trehalose is then maintained until just before the 50% survival point is reached. It is believed that the adults obtained from the field would fall well within limits investigated in the laboratory study here reported.