Warning signs - Butterfly Gear

The Lepidoptera Log - by Steve Woodhall

Warning signs

Don’t mess with me – you might regret it!

We’ve already looked at one defensive mechanism used by butterflies and moths to evade predation – camouflage.

But there’s another – warning colouration.

Warning colours appear to be universally recognised indicators of danger, with red commonly signifying threat. Lepidoptera also utilise additional visual signals, including yellow and black or black and white patterns. These warning mechanisms (known as aposematism) extend beyond butterflies and moths and are observed in other insect groups such as wasps and beetles. The effectiveness of such colouration and patterning depends on the ability of potential predators to perceive colours. Although other forms of warning, such as auditory and olfactory cues, exist, this discussion will focus specifically on the role of colours and patterns.

Warning coloration is not limited to diurnal species; numerous nocturnal moths employ ‘flash’ colours, which are only displayed when the organism is disturbed. A warning pattern or colouration typically indicates that an organism presents some form of threat, such as being poisonous—causing harm if consumed—or venomous—causing harm if it bites or stings. In certain cases, the organism may taste awful, serving as an olfactory deterrent. This is often referred to as ‘unpalatable’ versus ‘palatable’. However, this signalling is not always accurate, as many vividly coloured or conspicuously patterned insects are harmless. In these instances, the warning display functions purely as a form of mimicry or deception, sometimes referred to as ‘mocking.’

There are two main types of mimicry. In ‘Batesian’ mimicry, a harmless species (the mimic) resembles a harmful species (the model). ‘Müllerian’ mimicry involves multiple noxious species that share similar warning signals. Batesian mimics can reduce the effectiveness of warning signals for predators by making them less reliable, while Müllerian mimics may reinforce the warning effects among harmful species. Rather than being a matter of deliberate choice, the similarities in appearance among these creatures have developed over lengthy periods through evolutionary processes. As a result, many non-harmful insects as well as various harmful ones may display similar appearances.

We refer to such relationships as ‘mimicry rings.’ They exist everywhere, especially in the tropics. We have some examples in South Africa – let’s examine them more closely.

The first mimicry ring we’ll show you is the ‘orange with black-and-white wingtips’ ring. This has several palatable species as well as unpalatable ones. The most familiar one is African Plain Tiger Danaus chrysippus orientis, (Nymphalidae: Danainae) which is sometimes referred to as the ‘African Monarch’ from its similarity to the American butterfly. It gains its unpalatability from its habit of ingesting bitter alkaloids from certain plants. Some members of the ring are also unpalatable (or distasteful) like the White-barred Telchinia, Telchinia esebria form fulva (Nymphalidae: Heliconiinae) which gains its toxins from its larval host plants, like the Tree-nettle Urera tenax. Closely related is the Dusky Telchinia, Telchinia esebria form esebria. Monarch Looper Aletis libyssa (Geometroidea: Geometridae: Sterrhinae) is unpalatable because its larvae feed on the highly toxic foliage of Wild Loquat Oxyanthus speciosus and its relatives. That is from a totally different superfamily of the Lepidoptera, showing how far and deep Müllerian mimicry goes.

The female Common Diadem Hypolimnas misippus (Nymphalidae: Nymphalinae) is a palatable mimic that is extremely hard to tell apart from a Plain Tiger (this post shows you how). Going a little north from South Africa, in Zambia we find another very close palatable mimic, the Monarch False Acraea, Pseudonympha poggei (Nymphalidae: Limenitidinae). Likewise palatable is the female Mocker Swallowtail Papilio dardanus cenea form trophonius (Papilionidae), which shares a common pattern with the Plain Tiger but is easier to tell apart from it. Lowland Bush Beauty Paralethe dendrophilus indosa (Nymphalidae: Satyrinae) is a palatable mimic that is a little easier to tell apart. Given that we humans can see most of the differences between these (perhaps with a little prompting!) it might be easy to pooh-pooh this. But put yourself in the position of a hungry bird that’s just had a nasty encounter with a Plain Tiger, and you see a Bush Beauty flapping past. Edible or not? You decide! Are you feeling lucky today?

Now let’s look at another mimicry ring.

The ’Black-and-white’ or ‘Pied’ mimicry ring is extensive and covers several butterfly families as well as some moths. Southern Friar Amauris niavius dominicanus and Novice Amauris ochlea ochlea (both Nymphalidae: Danainae) are unpalatable models related to the African Plain Tiger with a similar chemical defence. Dusky Telchinia Telchinia esebria female form monteironis and female Dark Wanderer Bematistes aganice aganice are both Nymphalidae: Heliconiinae and derive their toxins from their larval host plants. They are a challenge to differentiate – the clue is the forewing upperside which in Dark Wanderer has a notch in the apical band and no white patch on the inner margin. White Bear, Nyctemera leuconoë (Noctuoidea: Erebidae: Arctiinae) is a diurnal moth related to the Tiger Moths – a group known for their unpalatable nature derived from caterpillar host plants. Its slow, hesitant flight pattern and pied markings make it easy to mistake for a Dusky Telchinia.

Moving to the palatable species, female False Wanderer Pseudacraea eurytus imitator is a good mimic of the female Dark Wanderer. Its pale upper side markings are closer to those of the female Dusky Telchinia Telchinia esebria form monteironis. It can be distinguished from both by the pale-ringed dark spots at the base of the forewings, and its porrect, as opposed to lax, antennae. It’s in the Limenitidinae subfamily of Nymphalidae, as is the related Southern False Chief, Pseudacraea lucretia tarquinea. That is a mimic of the Chief, Amauris echeria echeria, although it is not an exact colour match. To make this more confusing for you (and predators) these butterflies are often polymorphic. As well as the white form shown here there is a form with yellow markings. Another polymorphic mimic is the Variable Diadem, Hypolimnas anthedon wahlbergi (Nymphalidae: Nymphalinae) whose form wahlbergi mimics the Friar. It has a different form, mima, which appears below.

The small butterflies in the Lycaenidae are generally not as noted for aposematism as the Nymphalidae and Papilionidae. There are a few pied examples like the female Buxton’s Hairstreak, Hypolycaena buxtoni and the Black Pie, Tuxentius melaena melaena (both Lycaenidae: Polyommatinae). These are probably palatable, but we don’t know for sure. Another family with few pied members is the Pieridae (at least in South Africa – there are many such elsewhere). The only truly black-and-white one in South Africa is the female Diverse Albatross, Appias epaphia contracta form limbophora. Many Pierids are distasteful due to the chemicals in their larval host plants.

Going off the theory that more is better and large size reinforces the ‘I taste bad’ message, most mimics are large butterflies like the female Mocker Swallowtail, Papilio dardanus cenea form hippocoonides. This species that has forms mimicking most aposematic colour schemes.

There is another similar mimicry ring to the Pied one; black with yellow markings or pied forewings, yellow hindwings.

The Black-white-and-yellow (or Black-and-yellow) mimicry ring has some similarities to the Pied ring. Several of these species are polymorphic (they possess several colour/pattern forms or ‘morphs‘) and have forms that are part of both rings. The two best-known unpalatable models in South Africa are the Chief Amauris echeria echeria and Layman Amauris albimaculata albimaculata (both Nymphalidae: Danainae). These can be difficult to tell apart. The Chief shown here has yellow forewing spots but don’t be fooled… some individuals have white forewing spots! The Layman always has white forewing spots. The best way to tell them apart is to look at the trailing edge of the hindwing upperside yellow (or cream) band. In the Chief it is sharp edged, in Layman it is soft-edged. These two are models for several palatable species in the Nymphalidae and Papilionidae.

From mima of the Variable Diadem, Hypolimnas anthedon wahlbergi (Nymphalidae: Nymphalinae) is a good mimic of either of these Amauris species. It’s polymorphic – the other form, wahlbergi, mimics another Amauris, the Friar. Likewise, the yellow form of the False Chief, Pseudacraea lucretia tarquinia (Nymphalidae: Limenitidinae). This butterfly has a wide range of forms from white to cream to yellow, and the Northern False Chief Pseudacraea lucretia expansa even has a deep orange form. It appears that the shape of the pattern and the general colour make it a ‘multipurpose mimic’ of Chiefs and Laymen, as well as other Danainae that don’t occur in South Africa. Remember, these butterflies occur over a wide area of Africa as well.

Female Swallowtails (Papilionidae) often mimic Amauris species; the males looking different. Mocker Swallowtail Papilio dardanus cenea form silvicola is one form of the polymorphic female of this butterfly. There are several forms that mimic the Layman or the Chief; some have cream forewing spots and others bigger spots, yet others, smaller. This one illustrates it well. The male White-banded Swallowtail Papilio echerioides echerioides is black with broad white bands; the female, like the Mocker Swallowtail, mimics the Layman/Chief pattern. The two species fly together, and the females can be confused. There is only the one female form of Papilio echerioides and in general her hindwing upperside marginal spots are single or joined whereas in Papilio dardanus cenea form silvicola they are usually double.

The female Forest-King Charaxes, Charaxes xiphares penningtoni (Nymphalidae: Charaxinae) exhibits strong Layman/Chief mimicry. The colour of the pale markings varies from subspecies to subspecies. Some have yellow or cream forewing spots; some have white to mauve hindwing bands. This species’ male is very different in colour and patterns to the female, as shown here.

Next we’ll look at a very different mimicry ring – yellow with black spots/stripes.

The ‘Yellow-with-black-spots‘ ring is widespread across many families of Lepidoptera. It even stretches outside Africa to the Fritillary butterflies of Eurasia and North America.

Two examples (from the same subfamily as the Fritillaries) are the Polka Dot Pardopsis punctatissima, which like them has Violaceae as larval host plants, and Marsh Telchinia Telchinia rahira rahira. Polka Dot uses Pigea enneaspermus (Spade Flower) as larval host plant. It has no reputation for toxicity so the butterfly may be palatable but there is no evidence to support that. Marsh Telchinia uses Snakeroot Persicaria attenuata as its larval host plant. Although that plant is considered edible in Africa studies have shown potential toxicity at high doses. Therefore, the jury is out as to whether these are models or mimics!

Beautiful Tiger Amphicallia bellatrix (Erebidae: Arctiinae) is from a subfamily of moths with a well-deserved reputation for deriving toxicity from larval host plants. This species uses Rattlepods Crotolaria species that are known to carry toxins. Leopard Magpie Zerenopsis lepida (Geometridae: Ennominae) is from a tribe known to metabolise as larvae toxins from their cycad (Zamiaceae) host plants. These two species are probably models.

Spotted Buff Pentila tropicalis and Zulu Yellow Buff Teriomima zuluana (both Lycaenidae; Poritiinae, tribe Liptenini) have the typical aposematic colouring of this mimicry ring. This tribe uses lichens and cyanobacteria as larval food. It is likely that the adults carry bitter, toxic phenolic compounds derived from that. Many of them have aposematic colouration and are known to exude bitter smelling liquids when handled. These are also probably models.

Waterberg Acraea Copper Erikssonia edgei (Lycaenidae: Aphnaeinae) is from a group not noted for aposematism. Yet its larvae use a very toxic plant, Yellowhead Curryflower, Lasiosiphon kraussianus, as host. Other members of the subfamily use the same host plant but only this one has this warning pattern.

Macomo Ranger, Kedestes macomo (Hesperiidae: Hesperiinae) is from a small group of ‘Skippers’ that have bright aposematic patterns. Their larvae feed on grasses so this is probably a type of mimicry.

Now let’s look at a tribe of butterflies that specialises in aposematic markings and acts as models for many different mimics.

Butterflies in tribe Acraeini of Nymphalidae: Heliconiinae are known for their bright aposematic appearance and patterns of black spots on a pale ground. The most spectacular mimetic pair involving one of these species is the Acara Acraea, Acraea acara and its mimic, Boisduval’s False Acraea, Pseudacraea boisduvalii trimenii (Nymphalidae: Limenitidinae). In this case the mimic is twice the size of the model, possibly a case of message reinforcement for sight predators! Acara Acraea larvae feed on Adenia and Passiflora species (Passifloraceae) that are well known to carry toxic cyanogenic glycosides in their tissues. Pseudacraea larvae feed on plants in the Sapotaceae like Englerophytum natalense. These plants are not known to carry toxins.

The brightest red Acraeini are in the genus Rubraea, like the Blood-red Acraea, Rubraea petraea. This is one of the reddest butterflies in Africa and its underside carries a typical Acraea pattern of black spots on a paler ground. Its larvae feed on the African dog rose, Xylotheca kraussiana, in the family Achariaceae. This family has many species whose tissues are packed with cyanogenic glycosides, which release poisonous hydrogen cyanide (HCN) when the plant is eaten raw. But the African dog rose is the odd one out and is harmless – which makes one wonder whether the Blood-red Acraea’s traffic light red colour is a bluff or the real thing!

Unexpectedly, the Acraeini have mimics in the subfamily Hesperiinae of the Hesperiidae (Skippers and allies). These families are about as distantly related as it’s possible to be within the butterflies, but then again, some mimetic relationships spread across superfamilies. The two best known examples are Spotted Velvet Skipper Abantis tettensis (shown with a Wandering Donkey Acraea Acraea neobule neobule for comparison) and Variegated Acraea Hopper Fresna nyassae (with Tree-top Acraea, Rubraea cerasa, for comparison). It’s unlikely that the latter two are a true mimetic pair because they have different habitats. However, the Wandering Donkey Acraea and Spotted Velvet Skipper are avid hilltoppers in bushveld country, so they may share a protective resemblance.

Aposematism and its partner, mimicry, aren’t restricted to butterflies and moths. Hymenoptera (bees, wasps, and allies) carry a different threat to Lepidoptera. Whereas the latter are often poisonous (or pretend to be), Hymenoptera are often venomous – and have aposematic warning signals to advertise that. Some Lepidoptera have evolved ways to gain protection by mimicking them.

Many species of Lepidoptera mimic Hymenoptera. Probably the closest mimics are the Clearwing Moths in the family Sesiidae. These are relatively little-known in South Africa. Their larvae are usually stem borers. The species shown, Macrotarsipodes tricinctus, currently has no common name. They are extremely good wasp mimics. The Umbrella paper wasp Polistes fastidiatus, seen here preparing a butterfly caterpillar to feed to its grubs in the nest, shows this well. Narrow, clear wings, narrow waisted abdomen with yellow bands, and quivering, mobile antennae. Would you take a chance and pick one up?

Wasps can be brightly coloured, like the Spider hunting wasp, Java caroliwaterhousei. This one has paralysed a Palystes rain spider, which it will bury with an egg to provide food for its larva. There are several brightly coloured wasp mimics in the Arctiinae subfamily of Erebidae, tribe Syntomini. These include Splendorous Hornet, Euchromia follettii, Pleasant Hornet, Euchromia amoena, Heady Maiden, Amata cerbera, and Yellow Sleeved Maiden, Ceryx fulvescens.

The Bombycoid family, Sphingidae (Hawkmoths) has some clear-winged wasp/bee mimics around the world. The widespread Oriental Bee Hawkmoth, Cephonodes hylas virescens, is found in South Africa.

There are many more cases of aposematism and mimicry in South Africa and around the world. All I could cover here was a few of the better-known examples. Remember that all is not necessarily what it seems!

African Plain Tiger

Mocker Swallowtail ♀

Common Diadem ♀

White-barred Telchinia

Dusky Telchinia

Monarch False Acraea

Lowland Bush Beauty

Monarch Looper

Southern Friar ♀

Novice ♂

Dusky Telchinia ♀

Dark Wanderer ♀

White Bear

False Wanderer ♀

Southern False Chief white form

Variable Diadem

Buxton's Hairstreak ♀

Black Pie

Mocker Swallowtail ♀

Diverse Albatross ♀

Chief ♂

Layman ♂

Variable Diadem

Southern False Chief yellow form

White-banded Swallowtail ♀

Mocker Swallowtail ♀

Forest-King Charaxes ♀

Forest-King Charaxes ♂

Polka Dot

Marsh Telchinia ♂

Beautiful Tiger

Leopard Magpie

Spotted Buff

Zulu Yellow Buff

Waterberg Acraea Copper

Macomo Ranger

Acara Acraea ♂

Boisduval's False Acraea ♂

Blood-red Acraea ♂

Blood-red Acraea ♂

Spotted Velvet Skipper ♂

Wandering Donkey Acraea ♂

Variegated Acraea Hopper ♂

Tree-top Acraea ♀

Clearwing Moth (Sesiidae)

Umbrella paper wasp

Splendorous Hornet

Spider hunting wasp

Heady Maiden

Pleasant Hornet

Yellow Sleeved Maiden

Oriental Bee Hawkmoth