Feeding responses by female Pieris brassicae butterflies to carbohydrates and amino acids

Most Lepidoptera feed during the adult stage on carbohydrate-rich food sour ces, primarily floral nectar. However, little is known about the factors le ading to the acceptance of a possible food source. It is reported that butt erflies select for nectar rich in sucrose and amino acids. This suggests th at the insects have developed a sensitivity to these nectar compounds. We t ested females of the large cabbage white, Pieris brassicae L. (Lepidoptera: Pieridae) for their responses to 10 different nectar- or honeydew-sugars a fter either tarsal or proboscis stimulation. In no-choice experiments, food -deprived P. brassicae showed the strongest response to sucrose, followed b y fructose. Other sugars, including galactose, glucose, maltose, mannose, m elezitose, melibiose, raffinose and trehalose, did not elicit a feeding res ponse. Mixtures of essential or common non-essential amino acids did not st imulate feeding. In a choice situation, P. brassicae preferred sucrose over fructose, whereas they accepted a sucrose and amino acid solution equally to a plain sucrose solution. The results indicate that for P. brassicae, fe eding is mainly elicited by sucrose and fructose.