Eochroa trimenii
Felder, 1874

Male copyright Kirby Wolfe

This site has been created by Bill Oehlke at oehlkew@islandtelecom.com
Comments, suggestions and/or additional information are welcomed by Bill.

TAXONOMY:

Superfamily: Bombycoidea, Latreille, 1802
Family: Saturniidae, Boisduval, [1837] 1834
Subfamily: Saturniinae, Boisduval, [1837] 1834
Tribe: Bunaeini, Packard, 1902
Genus: Eochroa, Felder, 1874

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DISTRIBUTION:

Eochroa trimenii, The Roseate Emperor, (wingspan 50-70mm), occurs only in the southwestern portion of South Africa. This largely montane species occurs in Namaqualand (Kamiesberg Uplands) and the Richtersveld of the Cape Province, and is known from Garies in the south to Port Nolloth on the west coast and Kodaspiek of the Richtersveld in the north.

Eochroa is a primitive and isolated species with no known close relatives.

Rolf Oberprieler wites, "I have kept this sp. in Bunaeini for the moment, although Cooper's erection of a separate tribe for it (Eochroini) may in the end be valid."

Rolf indicates this species may also fly in Namibia.

Eochroa trimeni male, Namaqualand, Cape Province, RSA,
courtesy of John Kamps.

John Kamps indicates the date for the above specimen is October 1, 1990. This date would suggest a possible second brood. However, it is also possible that a live cocoon was exported from Namaqualand to a European or Northern Hemisphere nation and the pupa responded to photoperiod and emerged six months out of sync with its natural flight period. It is also possible that the original flight period of April to June is incorrect, but that information comes from Rolf Oberprieler, and I suspect it is accurate.

Eochroa trimeni set, courtesy of Dave T. Rolfe.

FLIGHT TIMES AND PREFERRED FOOD PLANTS:

The Roseate Emperor Moth flies in mountain habitats from April to June and there is one generation per year. Larvae feed on Melianthus species including Melianthus pectinatus (Touch-Me-Not), Melianthus dregianus, Melianthus minor and Melianthus comosus.

Eochroa trimeni female, Struder's Pass, near Garies, South Africa,
April 28, 2006, courtesy of Mike Buczkowski.

ECLOSION, SCENTING AND MATING:

Day-flying Eochroa trimeni moths pair for a very short time (10-15 minutes).

EGGS, LARVAE, COCOONS, AND PUPAE:

Brownish-pink eggs are laid in clusters of approximately twenty on hostplant leaves.

Early instar larvae skeletonize leaves but later feed from the edges and devour the entire leaf. Larvae feed during the day and hide at night and during inclement weather.

Larvae pupate near the base of the foodplant among dry leaves held together with a few strands of silk.

Johnny Marchant writes, "I saw the larvae down there (Kamieskroon) on Melianthus minor in the 3rd-4th instars, varying sizes, biggest a good 6cm long in late August-early September. We were there for the wildflower display so it was definitely early spring. It was also FREEZING COLD at night!! so they must really have a long summer diapause, plus being super cold-hardy. I kick myself every time I remember seeing them, and how the tour guide told me I could bring some on the bus if I wanted!!"

The larvae often are not full grown until early October when they drop to the ground and pupate in soil or amongst leaf litter near the base of the host plants.

Colouration suggests they would not be palatable to birds.

Larva copyright Kirby Wolfe

The western portion of southern Africa is hot and dry during their summer months (December-February in the southern hemisphere = June-August in the northern hemisphere). Pupae remain dormant in their flimsy cocoons during these months. Development and subsequent eclosions are probably triggered by the onset of cooler weather and the rainy season (March-April) when what was close to parched earth becomes fields of flower blooms.

I suspect the larvae are slow to develop due to the cooler temperature of their growing season and also due to the higher altitude of their habitat. The host plants need moist earth.

Larval Food Plants


Melianthus pectinatus.....
Melianthus dregianus
Melianthus minor
Melianthus comosus

Touch-Me-Not
Honeybush
Persian lilac
Melianthus

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"The Roseate Emperor moth is a flagship conservation species for the Kamiesberg Uplands. This spectacular, day-flying emperor moth is predominantly associated with the Kamiesberg Uplands, although a small population is also known from Kodaspiekin the Richtersveld. The genus is monotypic, and is considered rare. The caterpillar, which is bright white, ringed with black bands, feeds on various species of Melianthus (Melianthus minor, and M. pectinatus). The bright, showy colouring of both the larvae and moth (adults are bright pink with large yellow/black eye spots on each wing, wingspan 70 mm) suggest that they are aposematic, and unpalatable to predators such as birds. Adults fly April to June, during which time they lay eggs, and the new seasons larvae are fully grown by September to early October, when the larvae drop to the ground, and pupate in the soil at the base of their host plants, and emerge as adults the following winter."