Defence functions of mucus secreted from the larval body surface of the moth Phauda flammans

Abstract Many invertebrates and vertebrates secrete mucus from their body surface, which plays a crucial role in protecting themselves from attacks by microorganism or predators. This study reports on the potential functions of mucus secreted from the body surface of larvae of the moth Phauda flammans (Walker) (Lepidoptera: Phaudidae). We tested whether the mucus could inhibit the growth of the fungus Beauveria bassiana PfBb (Bals.‐Criv.) Vuill. (Hypocreales) and attract and/or deter predators such as the crazy ant, Paratrechina longicornis (Latreille) (Hymenoptera: Formicidae), and the predatory bug Eocanthecona furcellata (Wolff) (Hemiptera: Pentatomidae). Our results showed that de‐ and rehydrated mucus concentrations of 0.5–1.0 mg mL −1 had an inhibitory effect on the conidial germination and colony growth of B. bassiana PfBb; however, P. flammans mucus did not significantly affect fungal sporulation. Raw mucus and mucus concentrations of 1.0–4.0 mg mL −1 attracted P. longicornis workers in a Y‐tube olfactometer, whereas the physical viscosity of raw mucus hindered their foraging for food in a laboratory test. The E. furcellata adults did not display a preference for the odour of P. flammans mucus. Therefore, P. flammans mucus may inhibit pathogenic microorganisms and attract or repel predators, but the mucus does not act as a complete deterrent.