Silk recycling in larvae of the wax moth, Galleria mellonella (Lepidoptera: Pyralidae)

Galleria mellonella larvae spin protective tubes, which they use until they finish feeding, when they spin cocoons. A feeding choice experiment showed that some of the silk produced by feeding larvae was consumed in addition to the standard diet ( STD). To determine the effect of feeding on silk, last instar larvae were fed for 24 h on foods based on STD but modified by replacing the dry milk component (10% of the diet) with equal amounts of different kinds of silk. While each control larva consumed 21 +/- 0.5 mg of the STD and produced 4.5 +/- 0.1 mg of silk, larvae that ate the food that contained larval silk consumed 10 +/- 0.4 mg of food and produced 6.1 +/- 0.1 mg silk; the percentage ratio of silk produced to diet consumed was 21% and 61%, respectively. A more pronounced reduction in food consumption occurred when larvae were supplied with Galleria "cocoon" silk or the sericin fraction of such silk, and only 3.8 mg/larva was ingested of the diet containing Bombyx mori cocoon silk or its sericin fraction. Silk production expressed in terms of percentage of diet consumed was always higher than that recorded for larvae fed STD. We conclude that G. mellonella larvae recycle part of the silk that they produce during feeding. Presence of silk in the diet reduces food intake but increases the ratio of silk production to diet consumption. Sericin fraction of the cocoon silk seems to deter feeding.