Diario del proyecto Arctiinae of southern Africa

There are only two Rhodogastria species - R. amasis and R. similis.

They are pretty difficult to tell apart, especially as adults.

The caterpillars are quite different in later instars and this is what they look like:

Photos © @leejones and @suncana

The adults are more iffy:

Photos © @gawie @kooscl and @alexlamoreaux @riana60

I copy @beetledude 's notes here from https://www.inaturalist.org/observations/10915652 with updated links:

Telling apart the two Tricoloured Tiger Moths

Rhodogastria amasis

• The two lines on the thorax brown, not orange.
• Hindwing mostly white, or frequently with a peachy wash.
• Distribution: the Cape provinces.

Rhodogastria similis

• The two lines on thorax orange, not brown.
• Hindwing mostly orange.
• Distribution: 'further north'.

Caution:

• In comments on at least two observations, the facts about the colour of the thoracic lines have been reversed.
• In some moths it is difficult to decide whether the thoracic lines are orange or brown. If that is the case, err to the side of brown, except for specimens from KZN and further north.
• There are just two species of Rhodogastria in existence, namely the two above.

MAIN SOURCES:

• Moth expert Hermann Staude at https://www.inaturalist.org/identifications/23985427
• VÁRI, L., KROON, D.M. & KRÜGER, M. 2002. Classification and Checklist of the Species of Lepidoptera Recorded in Southern Africa. Published by the second author, Sasolburg, South Africa, and Simple Solutions, Chatswood, Australia, xxi + 385 pp.

This key is based on the descriptions in Häuser & Boppré's paper (see references below). Southern Africa in this key covers South Africa, Swaziland, Lesotho, Namibia, Botswana, Zimbabwe, Mozambique, Angola, Zambia and Malawi.

Distribution data is based on what H&B included from specimens only - therefore distributions are probably wider for most species than stated.

All photos included here are subject to ID confirmation!!!

The Key:

1a. Forewings white, ivory or very pale grey	2
1b. Forewings pale or dark brown, grey, grey-brown or ochre	9
2a. Large moth (33-36 mm forewing) with dark brown band along median and margin with transparent area between, distribution SA, Zimbabwe	A. magnifica Photo by Ricky Taylor
2b. Smaller moths without broad brown bands	3
3a. Abdomen white dorsally, yellow ochre ventrally, no spots on tergulae, distribution Angola	A. rufifemur
3b. Abdomen not as above, 1 or 2 spots on tergulae	4
4a. 2 spots on tergulae, abdomen red dorsally, white ventrally, distribution Angola	A. niveivitrea
4b. 1 spot on tergulae, abdomen variously coloured	5
5a. Femora yellow on the inner sides, abdomen yellow dorsally, white ventrally, distribution SA, Namibia, Zimbabwe, Zambia, Malawi, Angola	A. bubo Photo by Suncana
5b. Femora red on the inner sides, abdomen dorsally red or pink	6
6a. Forewing veins dark	7
6b. Forewing veins not dark	8
7a. Forewing white with a shade of grey or ivory, discal vein with a streak of dark scales, some-times another faded line postdiscally, length of fw 18-21 mm, abdomen dorsally bright red or pink, distribution SA, Mozambique, Zimbabwe	A. lupia Photo by Ricky Taylor
7b. Forewing plain white, discal vein not with a dark streak, length of fw 21-25 mm, abdomen dorsally red suffused with white scales, distribution SA, Swaziland, Zimbabwe	A. mulleri
8a. Hindwing margin concave, distribution Zambia	female A. leucoptera
8b. Hindwing margin not concave, distribution South Africa, Mozambique & Zimbabwe	female A. phaedra Photo by Magda (St Lucia)
9a. 2 spots on tergulae	10
9b. 1 spot on tergulae	11
10a. Abdomen dark red dorsally, pale grey-brown ventrally, forewing 21-24 mm, distribution South Africa, Mozambique, Zimbabwe, Malawi	A. affinis Photo by Ricky Taylor
10b. Abdomen pink-red dorsally, pale ochre ventrally, forewing 19-21 mm, distribution Zambia	A. luteibarba
11a. Abdomen yellow dorsally	12
11b. Abdomen red to pink dorsally	14
12a. Thorax creamy white, distribution Angola	A. brunnea ssp. brunnea
12b. Thorax grey to grey-brown	13
13a. Hindwing outer margin distinctly concave towards the anal angle which forms a short projecting edge posteriorly, forewing greyish brown, distribution SA, Mozambique, Zimbabwe, Malawi	A. bipartita
13b. Hindwing outer margin not or only slightly concave, without the anal angle projecting posteriorly, forewing pale grey to greyish white, distribution Mozambique, Zimbabwe	A. brunnea ssp. bipartitoides
14a. Forewings with large transparent areas	15
14b. Forewings densely scaled without large transparent areas	16
15a. Forewing length 27-30 mm, hindwing pale brown-ochre (weakly scaled), outer sides of femora and tibiae pale ochre, inner sides of femora, tibiae, and tarsi red, abdomen pink-red dorsally, pale ochre ventrally, distribution SA, Mozambique, Zimbabwe	A. bauri Photo by Magda (St Lucia)
15b. Forewing length 20-24 mm, hindwing almost transparent, pale grey-brown at the apex and along the outer margin, outer sides of fore & mid tibiae and tarsi brown, outer sides of coxae, femora and hindlegs grey-white, inner sides of legs pink-red, abdomen bright pink-red dorsally, grey-white ventrally, distribution SA, Swaziland, Namibia, Mozambique, Zimbabwe, Zambia	A. vitrea ssp. vitrea Photo by Ricky Taylor
16a. Forewing upperside pale to dark brown, with the discal cell and postdiscally the area between radius and vein m3 transparent, hindwing dark brown anteriorly and pale ochre posteriorly, distribution Zambia	male A. leucoptera
16b. Forewing upperside pale brown without clearly transparent areas, hindwing uniformly yellowish, distribution SA, Mozambique, Zimbabwe	male A. phaedra

REFERENCE
HÄUSER, C. & BOPPRÉ M. 1997. A revision of the Afrotropical taxa of the genus Amerila Walker (Lepidoptera: Arctiidae). Systematic Entomology 22(1):1 - 44. (Abstract on ResearchGate)