Sugar preferences and feeding strategies in the hawkmoth Macroglossum stellatarum.

Hummingbird hawkmoths were tested for their preferences for different types of sugar. In triple choice tests, moths sucked for longer periods from sucrose than from fructose and glucose. Naive moths released in a large flight cage and monitored over 24 days, drank on average 137 mul sucrose, 67 mul fructose and 7 mul glucose daily. In an independent test, moths spent more time feeding from sucrose than from fructose and more time feeding from fructose than from glucose. Animals in hibernation made less but longer feeding bouts, whereas animals that fed every day and newly eclosed animals were more likely to make more but shorter visits to feeders. The hawkmoths learned to associate colour with the preferred sugar. In a dual choice test, flower-naive moths chose blue rather than yellow artificial flowers. After the initial test, these animals received sucrose from the yellow and glucose from the blue feeders. A week later they chose yellow more frequently than blue indicating that they had learned to associate a colour with the preferred type of sugar.