We derive and study an SEIS deterministic differential equation model for endemic malaria with variable human and mosquito populations. Mosquito deaths in earlier life stages and a delay, T , to cater for the time lapse between egg laying and adult mosquito eclosion are explicitly included. For T = 0, oscillatory solutions are not possible. Conditions are derived for the existence, uniqueness and stability of the equilibria in the model. We show that the stability or instability of the positive vector equilibrium solution depends strongly on the size of the parameter T . We identify a threshold parameter R0, and show that the disease free equilibrium always exists and is locally and asymptotically stable when R0 < 1. We show that the prevalence of malaria in endemic regions can be discussed simply by measuring the proportions of susceptible humans and mosquitoes at equilibrium.