Millar's Tiger Moth

Millar’s Tiger moth (Callioratis millari) is one of a few species of ancient moths that can be regarded as living fossils called the diptychines. There are sixteen known species of diptychines, all confined to Africa.

The intimate relationships between cycads and diptychines makes one wonder if the diptychines are indeed remnants of a distant past as are their hosts. Fossil Lepidoptera are rarely found and no diptychine fossils are known. To attempt an answer to the questions of antiquity and former glory one is therefore left only with circumstantial evidence. The few known Lepidoptera fossils indicate that the extant families and subfamilies were already established by the late Triassic. Moth families are generally characterized by the specific arrangement of the veins on their wings, which is stable for each subfamily. The diptychines are the exception. They have a very unstable wing venation, with the different genera and even species having patterns of wing venation that do not always match each other and do not fit into any of the classic subfamilies. As a result taxonomists in the past have shifted ditychine genera in and out of four different subfamilies. Diptychines are characterised by their close association with cycads and by unique structures in the larvae, genitalia and tympanal organs (Staude,2001). Diptychine genera do not contain many species and genera are not closely related. Species within the genera are distinctive and have often developed elaborate, unique pheromone dissemination structures.The majority of species are very restricted in their distribution, even more so than their cycad hosts, and have become specialised in their preferred habitat. This makes them very vulnerable through habitat loss and indeed one species Millar’s Tiger (Callioratis millari) is on the brink of extinction, barely hanging on in it’s unique Stangeria/grassland habitat at Entumeni, KwaZulu-Natal.

Millar’s tiger moth is the most threatened of the Callioratis species. It disappeared from it’s type locality circa 1928 and had not been seen for over 75 years despite efforts by the author, N. J. Duke, A. I. Curle and a media campaign to try and relocate it. It was regarded as extinct untill a specimen was found by Glen Holland, the local conservator, at Entumeni Nature Reserve some 120km from the type locality, in 1997. After having established the species’ foodplant and habitat during 1998, the author and A. I. Curle in collaboration with local Stangeria eriopus experts embarked on a survey of all known likely localities from Mtwavuma Reserve in the south to Ngoye Forest Reserve in the north of KwaZulu-Natal (unpublished reports to KZNNCS, 1999, 2000, 2001). To date the species has not been found outside of the Entumeni area. In the Entumeni area C. millari is restricted to three small patches of grassland surrounded by forest, cultivated land or unsuitable drier grassland. In one of the patches the species seems to be reasonably well established, in an adjacent patch found only rarely and in the third patch only a few larvae have been found. All three localities are within 5km of each other: two within the Entumeni Nature Reserve and another on private land. On a government website on the state of South African environmental management, C. millari is one of only two threatened invertebrates mentioned. The conservation status of C. millari can be regarded as endangered.

In recent years, adults and larvae of C. millari have only been found in two open grassland patches surrounded by coastal scarp forest (on one side a gravel road) within the boundaries of the Entumeni Nature Reserve and on a small wet patch, surrounded by drier grassland, nestled against a hillside on private land. These grassland patches support a good number of low growing Stangeria eriopus plants. No other cycads occur in the grassland although both S. eriopus and E. villosus occur under the surrounding forest canopy. Old records indicate that the type locality is in the area between Kloof, Gillitts and Hillcrest railway stations near Durban, South Africa. This area is today virtually built-up and original grasslands have long been destroyed. The last record for C. millari from this area was 1928. Adults of C. millari were only seen to fly within the confines of the two grassland islands at Entumeni. No adults were seen to venture into or over the surrounding forest. It appears that the range of C. millari is restricted to this grassland habitat and that it will only breed in the grassland in spite of plentiful available foodplant under the canopy of the surrounding forest and in grasslands at lower elevations.

Both the original type locality and the Entumeni locality are higher than 700m above sea level. Many areas of grassland containing good quantities of Stangeria eriopus are still found in KwaZulu-Natal at lower elevations. In spite of extensive searches over the past few years in these areas, no sign of C. millari occuring in these apparently suitable habitats was found. (Staude unpublished reports to KZNNCS, 1999, 2000, 2001). Diptychines generally have a secondary food source (Staude, 1994) and some species have specific secondary foodplants (e.g. Durbana setinata utilize only certain flowers as a secondary food source, Staude, unpublished). It is therefore suspected that C. millari may have a preferred secondary foodplant in addition to its’ primary foodplant (S. eriopus), which possibly only grows in suitably wet grasslands higher than 700m above sea level. Such a secondary foodplant would explain the absence of C. millari from the large areas of apparently suitable habitat.

We are lucky- that we are still able to observe living cycad moths together with their associated foodplants - that we are able to observe how they interact with each other in their natural state and that we do not have to try and recreate a fantasy Jurassic Park, because we have pieces of the real thing in the remnant bits of cycad ecosystems scattered all over Africa. It is incredulous that we attach so little value to these unique ecosystems and it is sincerely hoped that we can stem the tide that is threatening to destroy, in the time of a few human generations, what Nature has preserved for many millennia.