Lipids have been little investigated as food for adult insects, considering the importance of these macronutrients for development and reproduction. Lipid reserves are essential for oogenesis and somatic functions. Through host‐feeding, parasitoid females obtain essential nutrients, including lipids used in reproduction. The present study determined the lipid profile of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae), a factitious host of Trichogramma parasitoid wasps, and evaluated whether the fertility of the parasitoid was increased by supplementing its diet with oils having a lipid profile similar to that of the host. Females of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) fed continuously with a diet composed of 90% honey and 10% vegetable oil, mixed in a water bath at 70 °C, parasitized significantly more eggs (11–18%) than did females fed only with pure honey. However, addition of the oil reduced the longevity of these wasps by 40% compared to the controls fed with pure honey. The oil‐enriched diet did not affect the flight performance and quality of the offspring. This information on the use and allocation of lipid reserves in T. pretiosum will help to increase the parasitism capacity of this important biocontrol agent, when produced by mass rearing.