A Most Primitive Moth

Meet Sabatinca sterops, one of the world's most primitive moths. Fossils of related species in the family Micropterygidae have been found in amber in Lebanon that date back at least 120 million years.

But why is it considered "primitive". Well, it bears the following combination of characteristics: chewing mouthparts (most Lepidoptera have sucking mouthparts or no mouthparts at all as adults); raised hair-scales and the forewings and hind wings are similar in shape and venation. These are considered basal features in the Lepidoptera.

Nine Australian micropterigid species are known. Most occur in eastern rainforests including Tasmania. Several species are purplish or with dark bands and are of similar size. All are presently included in the genus Sabatinca but have been divided into two groups. One, "The Australian Group", includes the "golden species" of which S. sterops is a member.

We encountered large numbers of this moth recently on the lower slopes of Mt Lewis (ca. 700 m), Queensland. They were most active dusk and shortly thereafter. Mt Lewis is covered by rainforest and it is incredibly dry at this time of the year. Some saplings are wilting because of the lack of moisture. Larger trees are dropping leaves. the undergrowth of annuals is mostly dead. So it was surprising to see this small moth flying in large numbers in the undergrowth.

S. sterops measures only 2.5 mm from head to tip of wings. The adults are said to visit flowers where they feed on pollen. Little is known of the whereabouts of the larvae of many species. Some have been found in rotting logs. It is hard to imagine the tiny caterpillars surviving in the dry soil of the rainforest. They may be associated with liverworts or other primitive plants present on branches or rocks.

S. sterops is known from specimens taken from Cooktown to Mission Beach, Queensland. With the tens of specimens we found at our site on Mt Lewis, there must be millions of the moths spread over its geographic range.


Literature
Zborowski, P., Edwards, T. 2007. A Guide to the Australian Moths. CSIRO Publishing, 214 pp. Collingwood, Vic.