Observations on the fecundity ofMylabris pustulata maintained on two different food plantsIpomoea cornea andIpomoea tuberosa, with males and females reared separately on the flowers of these two host plants are discussed.Mylabris pustulata reared onIpomoea cornea laid 144±30·80 eggs while that onIpomoea tuberosa only 93±38·87 eggs. The chemical composition of the flowers ofI. cornea andI. tuberosa revealed that protein concentration is greater inIpomoea cornea (4·88%) thanIpomoea tuberosa (4·64%). The quantity of food ingested is also greater when reared onIpomoea cornea (1055 mg). In the light of these observations it is presumed that the food rich in protein concentrations is among the principal factors influencing fecundity.