Observations on larval tunneling by the enigmatic South African Keurboom Moth Leto venus (Cramer, 1780) (Lepidoptera: Hepialidae)

Abstract

Details of tunneling and feeding by larvae of Leto venus are described and illustrated for the first time. Larval tunnels were examined from a section of lower trunk of the host plant Virgilia oroboides ferruginea from the Garden Route Botanical Gardens. Tunnels were 255-324 mm in length and of irregular cross sectional shape and located in the outer cortex and phloem, sometimes intersecting bark. Emergent pupae protrude from the host, sometimes from a ‘cocoon’ of silk and debris that also forms a tubular extension beyond the bark surface. The location of tunnels and their short length relative to the size of the larva and duration of larval development suggests that larvae are not primarily wood consumers, but utilize a replenished food supply, perhaps grazing phloem resulting in a sustained release of nutrient rich sap. The tunneling and feeding mode of L. venus provides new insights into possible modes of evolutionary transition between general tissue feeding found in many root feeders and callus feeding that occurs in other stem boring Hepialidae.