In addition to taking blood-meals, mosquitoes regularly feed on the nectar of plants. The nectar, in particular the sugar it contains, serves as their main source of energy, and therefore underlies many aspects of the mosquitoes life-history traits, including their longevity. To understand better how different nectars and sugars influence the longevity of mosquitoes, we let mosquitoes feed on several plant species (the flowers of Thevetia nerifolia, Mandalium coromandelianum, Ixora coccinea, and Tabernanthe iboga, and the fruit of Carica papaya), measured the concentrations of sucrose, fructose and glucose in the nectar and fruit juice, and measured the size of their sugar meal and their longevity. The plant the mosquitoes fed on affected their longevity (which ranged from an average of 8.2 days when they fed on C. papaya to 21.1 days when they fed on M. coromandelianum) and the size of the sugar meal. While mosquitoes that fed on the plants from which (in a separate experiment) they took larger meals lived longer, their longevity was not affected by the concentrations of glucose, fructose, sucrose, or total sugar in their diet. We also let mosquitoes feed on different sugars (glucose, sucrose, fructose, or trehalose) at concentrations of 1.97 or 19.97 kcal per 100 ml and measured their longevity. Mosquitoes lived approximately one week longer when fed sugar at the higher concentration, and lived longest (14.1 days) when fed with sucrose and shortest (4.8 days) when fed with trehalose. Overall our results show the importance of nectar and sugar feeding in determining the longevity of mosquitoes, but suggest that non-sugar