On Oct 2, 2006, Magpye from NW Qtr, AR (Zone 6a) wrote:
The Scyrotis athleta .. is also known as one of the 'jumping bean moths' of South Africa.
In the sand and leaf-litter beneath Rhus lucida, one can sometimes see small (about 6 mm) oval 'beans' that jump. In the 'bean' is the larva of a moth; Scyrotis athleta.
The movement and jumping is a response to heat and facilitates repositioning of the 'bean' into ideal pupating conditions in the soil and leaf-litter. It is quite a mystery how such a small larva in such a confined space is able to exert the force required to jump (up to 10 cm). Janse (1920) concluded that it is done by careful positioning inside the 'bean' and rapid contracting and relaxing of muscles.
The 'beans' start off as bumps (galls) that form on the leaves of Rhus lucida. A female moth lays her egg probably by inserting her ovipositor into the leaf. The gall is formed around the hatched larva possibly as a result of the feeding action inside the leaf. This is still being investigated. The larva feeds inside the gall and when mature the external layer of the gall bursts open and the 'bean' falls to the ground. Jumping can continue for up to 6 weeks and the moth emerges a few months later.