The feeding behavior of Trichogramma brassicae: new evidence for selectiveingestion of solid food

A descriptive study of the feeding behavior and structures of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) was conducted. Based on direct observational and biochemical evidence, larvae feed predominantly o n particulate materials, starting ca. 25 h post-oviposition. Feeding lasted for ca. 9 h, at 25 +/- 1 degrees C. During this feeding period the shape o f the larvae changed from vermiform to pyriform and then to sacciform, resu lting in a ca. 40-fold increase in body size. Larvae used elaborate feeding behaviors as they pulled solid food particles to their oral opening, broke small particles from larger ones, and took the particles into the stomodae um, which is a powerful pump. In the stomodaeum, peristaltic movement furth er macerated the particles, which eventually passed through the cardiac val ve into the midgut. As indicated by changes in fluorescently labeled casein , digestive enzymes aid in the extra-oral chemical digestion of food. The c ontents of the gut, during and shortly after feeding, were almost entirely closely packed solid particles. The behavioral activity of feeding larvae c entered almost exclusively on processing and ingesting solid food particles . The rapid larval growth is much more plausibly explained by their feeding on the highly concentrated nutrients found in solid foods, rather than the extensive concentration required if dilute liquids were the principal sour ce of nutrients. The implications of these findings for the development of practical artificial diets are discussed.