Assessment of plant tissue feeding by sand flies (Diptera: Psychodidae) and mosquitoes (Diptera: Culicidae).

Plant tissue feeding by Culex pipiens molestus (Forskål) was determined by identification of plant residues, differentially stained with Calcofluor, in dissected mosquito guts. Such residues were found in 42.3% of 286 field-caught mosquitoes. A method for determination of plant tissue feeding from specific sources is described. Before feeding branches were suffused with Calcofluor stain which binds to plant cell walls; stained residues of this tissue in the insect gut are indicative of feeding. Laboratory experiments with Phlebotomus papatasi (Scopoli) and C. p. molestus verified that feeding on labeled and untreated branches was similar. These experiments quantified the frequency of feeding by sand flies on 15 plant species and by the mosquitoes on 6 plant species. Labeled branches of plants that were fed upon frequently in the laboratory were used as baits in field tests. In the laboratory, the percentage of P. papatasi feeding on Prosopis farcta (Macbride) was 75.8% and on Ricinus communis (L.) 67.2%, whereas 29.4 and 17.9% of the sand flies caught in the field near labeled plants were marked, respectively. Similarly, 84.8% of the C. p. molestus fed on Ochradenus baccatus (Delile) in the laboratory and 11.0% of the mosquitoes caught near labeled baits were marked. These experiments show that plant tissue is common in the diet of C. p. molestus in the Jordan Valley, and that the plants tested in the field are natural sources of this diet for either sand flies or mosquitoes.