What do butterflies eat?

Text Steve Woodhall Photographs Steve Woodhall and Allison Sharp

Everyone thinks this is a very easy question to answer. Butterflies sip nectar. Butterflies come from caterpillars. Caterpillars eat leaves – simple, right? Well, not really…

Let’s start off with an example we think we all know. The larva (or caterpillar – the terms are interchangeable) of the African Monarch, Danaus chrysippus orientis, is well known to feed on plants of the Asclepiadaceae – broadly speaking, Milkweeds. Its famous, similar but larger, American cousin, the Monarch, Danaus plexippus, is sometimes called the ‘Milkweed Butterfly’, because its larvae use a plant of that name. Our African Monarch, and its Amauris relatives in the subfamily Danainae – Friar A. niavius dominicanus, Novice A. ochlea, Layman A. albimaculata, and Chief A. echeria – all use Asclepiadaceae as larvae.

All these butterflies are brightly coloured or patterned in black, yellow and white – patterns thought to be deterrent to birds looking for a meal. They closely resemble many other species of butterflies and moths from other families, and the theory went that they gained protection from this. The bright patterns led often enough to a bad taste experience for birds, to put them off anything that looked similar, we thought.

Many Asclepiadaceae are toxic plants, and it is likely that the caterpillars are able to metabolise their poisons and use them as defences against birds and other vertebrate predators. But many plants in that family are not toxic; in fact several are eaten by people in Africa, notably the genera Asclepias and Ceropegia. It used to be thought that the toxins ingested by the larvae were carried through to the adults, but if that were the case, would not the toxic effect be diluted enough to make it ineffective? But studies showed that the majority of adults repelled birds. Why?

It’s been long known that all adult Danainae don’t only imbibe nectar from flowers. Certain plants, when wounded, attract large numbers of males, who swarm around them, sucking at the leaking sap as if they were flowers. We now know that such plants, under stress, exude bitter tasting chemicals that deter herbivores. These chemicals are called pyrrolizidine alkaloids and the butterflies can metabolise them to create their own deterrents. The males even create from them pheromones to attract females! And when they mate, the male passes across a little package of alkaloids with his sperm, allowing the females protection as well.

This African Monarch Danaus chrysippus orientis and Novice Amauris ochlea are imbibing alkaloids from wilted Heliotrope plants that have been cut by a lawn strimmer.

This Layman Amauris albimaculata is sucking the leaves of a dead, brown Senecio plant.

Some butterflies hardly touch nectar at all. The big, charismatic Charaxes butterflies, in the subfamily Charaxinae, are seldom seen because they keep to the forest canopy. Many butterflies in the family Nymphalidae are partial to a bit of fermenting fruit, but Charaxes take it to extremes. Not only are they attracted to anything that gives off a whiff of alcohol, but also fouler stuff like faeces and dead animals.

The best way to see lots of Charaxes is to find a ‘sucking tree’. Beetle larvae bore into the living wood of trees, which leaks sap, which ferments. It often drips down the bark, attracting a motley crew of Charaxes and other butterflies, beetles, ants, flies – the works.

A tree branch weeping sap from beetle larva tunnels has attracted two female Blue-spotted Charaxes Charaxes cithaeron, and a male Green-veined Charaxes, C. candiope.

Any pile of faeces is likely to attract Charaxes. Carnivore dung is very good, but so is that of elephants and monkeys.

Even cow dung sometimes does the trick – here is a male Black Charaxes (not sure if it is Demon C. phaeus or Van Son’s C. vansoni – the undersides are alike) stocking up on second hand nutrients. Yum!

Sometimes, it’s a mystery what the butterflies are actually feeding on. Occasionally one sees them sitting on grass heads, sucking contentedly, easy to approach. It’s usually either African Monarchs or one of the two Joker species (Spotted, Byblia ilithyia or Common, B. anvatara acheloia) that do this. At times, dozens can be seen at once.

This dry season form badiata of Spotted Joker Byblia ilithyia is feeding on a grass head. And it’s well known that grass flowers have no nectar! There are numerous theories as to why this should happen. They vary from moisture making grass seeds ferment (and give off alcohol) to tiny mites sucking the grass head and leaking sap – which ferments. But this behaviour is often seen in ultra-dry conditions, with no rain having fallen for months. And why is is always these three species and not others?

All the above examples are from the Brush-footed Butterflies or Nymphalidae. Using fermenting fruit, tree sap, dung and rotten flesh is actually quite a common feeding strategy in these insects, but the caterpillars are largely plant feeders.

For really weird feeding habits we turn to the Lycaenidae or Gossamer-winged Butterflies. With these, both the adults and the caterpillars get into the act. Around Kloof we are lucky enough to have quite a few of these strange insects. In November and December, in places where grassy hillsides are covered in sandstone boulders, we can find Rocksitters, subfamily Poritiinae. These little butterflies are aptly named because they like to sit on… rocks!

Here is a tiny little male Yellowish Amakosa Rocksitter, Durbania amakosa flavida, sitting on a lichen-covered rock near Key Ridge. The underside looks just like lichen, but the upper side is orange and black. These little butterflies are actually distasteful, just like a Bitter Acraea – the upper side colours are a warning. When molested they emit a bitter, acrid-smelling liquid.

Amakosa Rocksitter caterpillars take a whole year to grow to full size, and they spend this time grazing lichen off the rock surface. Finally in spring they form a chrysalis (or pupa – the terms are interchangeable) and the adult emerges in late spring to early summer.

This is one of many examples of lichen feeding among Gossamer-winged Butterflies; it is actually a fairly common feeding strategy in the tropics – but Rocksitters are endemic to South Africa. They are found nowhere else. Although widespread, the individual colonies are vulnerable to habitat destruction by farming, forestry and developments. Like a few other butterflies, the adults do not feed. Their mouthparts are atrophied. They emerge with all the energy they need to find a mate, copulate and lay eggs (if a female) before dying.

Another group of the Lycaenidae whose larvae feed on lichen are the Buffs, whose larvae use lichen growing on trees. These are also subfamily Poritiinae, but the adults are able to feed. But not on nectar… honeydew is their favourite tipple.

This little Common or Natal Buff, Baliochila aslanga is sucking honeydew from a scale insect.

Scales are flightless insects which suck the sap from twigs and branches, and concentrate the sugars in their bodies. The excess liquid, still containing some sugar and proteins, is excreted – much to the advantage of the butterflies!

Scales are not the only insects that exude honeydew. The best-known are aphids, and tree hoppers. Of course, ants are also fond of these secretions – and some butterflies are fond of the ants… there are some butterflies whose caterpillars live inside ants’ nests and prey on the ants’ young. And even stranger are the parasitic Skollies (genus Thestor, subfamily Miletinae) whose caterpillars are totally non-plant eating.

Some Skollies’ larvae are even fed by ants, just like a baby cuckoo – as shown by this Peninsula Skolly, Thestor yildizae, from Cape Town. (photo by Alan Heath) This one is being fed by Pugnacious Ants, Anaplolepis sp. These are the ants that farm termites, so the butterflies are often found near termite mounds.

Basuto Skolly Thestor basutus caterpillar feeding on a cottony cushion scale insect, Pulvineria icenyi. (photo by John Joannou) These caterpillars also live insides the nests of Pugnacious Ants, where they are cuckoo parasites.

A female Basuto Skolly laying eggs on grass near a colony of scale insects, close to a Pugnacious Ant nest, near Inanda Dam. It is quite common in the Kloof area. There are large colonies in grasslands near Inanda Dam, Crestholme and Peacevale.

Upper side of a female Basuto Skolly. Skollies are another group of butterflies whose adults cannot feed – but unlike Rocksitters they have a fast and sustained flight.

You may very likely find a relative of the Skollies in your garden. Woolly Legs (also Miletinae, genus Lachnocnema) are common, dull coloured little butterflies with beautiful metallic patterns on their undersides. Unlike Skollies the adults can feed – and they never use nectar – only honeydew from aphids, plant hoppers and scale insects. You might see a bunch of these appealing little creatures mobbing a patch of aphids – as good a reason not to use insecticides as I can think of!

This male Southern Pied Woolly Legs, Lachnocnema laches, is sharing honeydew from young scale insects with a group of ants. The picture was taken at Cotswold Downs during a Kloof Conservancy Open Gardens event.

Woolly Legs caterpillars shelter inside ants’ nests during the day, coming out at night to prey on insects. They have elongated ‘true’ legs with which they catch their victims. This Southern Pied Woolly Legs has hooked itself a plant hopper nymph (photo – Allison Sharp). The hoppers move quite quickly but the caterpillar is able to immobilise them immediately with one bite – a sign that they might perhaps be venomous, which is a Ph.D waiting for some young lepidopterist!

Even when they eat plant matter, Lycaenid larvae do it differently. Most of them have a preference for high protein food sources, which allows them to grow quickly and pack a lot of energy into a small frame. Many eat growing shoots, and seeds. The latter are very popular and it’s often a case of young caterpillars eating immature seeds in flower ovaries and moving onto full sized seeds (or other insects) later as they grow.

Playboys, like this Orange-barred, Virachola diocles, are fond of legume seeds. This fully grown caterpillar is eating the nutritious beans found inside a pod of the attractive scrambling plant, Pride-of-the-Kaap, Bauhinia galpinii.

Often all you can see of a Playboy caterpillar is its rear end blocking the hole it has eaten in the pod. The holes make it easy to find the larvae and it’s fun to rear them to adulthood.

Playboys are often very brightly coloured, like this male Orange-barred. The females are usually dull brown or grey.

Theclinae, the subfamily that the Playboys belong to, has many seed-eating species. These are found all over Africa and into the East. Their close relatives the Protea butterflies are confined to Africa and as their common name suggests, are associated with Protea plants.

Proteas are among our most iconic flowers, and it’s fitting that one of our most beautiful butterflies uses them exclusively as host plants. This fat grub, caterpillar of the Russet Protea, has grown from the egg inside one Protea bud, eating all the seeds, which are packed with proteins and fats.

The affected bud never opens, but simply turns brown and doesn’t grow to full size. As with Playboys this makes the caterpillars and chrysalides easy to find. Here is a Russet Protea chrysalis, formed inside a Protea bud it hollowed out when it was a caterpillar.

Protea butterflies are among the largest Lycaenidae and the males are often brilliant scarlet or orange – like this Russet Protea.

Finally, there are some other butterflies that drink other things than nectar. Whites, Yellows and Tips (Pieridae) and Swallowtails and Swordtails (Papilionidae) are often seen (sometimes in large numbers) on wet muddy patches along paths or near water. Blues are also seen doing this. If you look carefully, it is nearly always males doing this.

The most attractive mud puddles are those which have been urinated on by animals. Dead animals such as crustaceans or fish are also visited. The reason is, butterflies, like antelope, are largely herbivores. Even if the larvae feed on other animals, those adults that feed on nectar are faced with the same challenge as all herbivores – where to find vital inorganic salts? Male butterflies need these to develop their sperm, without which they cannot fertilize their mates.

Butterflies are often found around salt licks, or bones of dead animals. But one of the best sources of salts (and the easiest to procure) is urine. Male urine tends to work best because it contains male hormones that attract the butterflies.

These male Ant-heap Small Whites Dixeia pigea are congregating on a patch of damp earth that contains dissolved salts from a nearby mineral deposit.

This male Small Striped Swordtail Graphium policenes has found a patch of mud that’s been enhanced by (male) human urine.

If the mud has been enhanced by a mix of urine and dead crustaceans or fish, it can be a powerful attractant. This male Citrus Swallowtail Papilio demodocus is sucking up moisture from a mud puddle that has had a bucket of fermenting prawn shells and urine poured over it. Photography in these circumstances is best done from an upwind direction!

Steve Woodhall is a butterfly enthusiast and photographer who began watching and collecting butterflies at an early age. He is President of the Lepidopterists’ Society of Africa, and has contributed to and authored several books, including Field Guide to Butterflies of South Africa and the popular What’s that Butterfly?