A small (1cm) white and brown mottled moth with an astonishingly close resemblance to its cousin, S. ecclesialis, the Salvinia stem-borer feeds on many types of aquatic plants, including water lettuce (Pistia stratiotes) and, of course, Salvinia rotundfolia, a water fern.
Since its caterpillars can do a lot of damage to those plants, even to the point of killing them, S. multiplicalis has been introduced as biological control for Salvinia molesta, an invasive species, in Australia.
The caterpillars can be seen on the host plants feeding in groups, where they collectively construct a silk canopy over their feeding site to protect it, expanding it as they run out of food and move on. The life span of this moth, from egg to adult, is only about three to four weeks.
Here’s how to tell Samea multiplicalis from Samea ecclesialis.