Diet Ingestion and Destination in Culiseta inornata (Diptera: Culicidae): Effects of Mouthpart Deployment and Contact of the Fascicle and Labellum with Sucrose, Water, Saline, or Atp

Abstract

Diet ingestion and destination in female Culiseta inornata (Williston) is controlled by a complex sequence of stimuli which include the phagostimulants in the diet. Attached animals with their mouthparts separated were stimulated by having combinations of solutions applied to the labellum and the end of the fascicle. A solution on the fascicle contacts the labral chemoreceptors and, if there was any ingestion, receptors in the cibarial region. An amount of 1 M sucrose, saline, adenosine triphosphate (ATP) in saline, or water applied to the fascicle had a much greater effect on diet ingestion and destination than did the same solutions applied to the labellum. ATP in saline (1 mM) at 20°C was applied to the fascicle and induced 70% of the test insects to gorge. Consequently, separation of mouthparts is sufficient to facilitate the ATP response and a heat signal is not necessary. Artificial mouthpart separation produces different results than normal mouthpart deployment through a membrane. It enhances the ingestion of saline and biases the diet destination of 1 M sucrose. Normal mouthpart deployment through a membrane reduces the response to sugar, and blocks the ingestion of water completely. The results illustrate the complexity and the integration of the various stimulus-response events involved in the feeding behaviors of mosquitoes.