Some years ago, a gardener told me she was enjoying the butterflies in her garden. It was early in a sunny September, and a range of butterflies flapped their vibrant wings around the nectar-filled blooms in her compact, warm sun-trapping garden. Did she grow any plants to encourage the butterflies to breed?
No, came the emphatic answer. She hates caterpillars.
But you cannot have butterflies without caterpillars.
No, she still didn’t want them.
The clarion call to save biodiversity is a cry that meets with broad public support nationally and internationally. Yet for many people, conservation is something that happens somewhere else. It is not. It is everyone’s responsibility. Covering your garden with artificial grass, tarmac, concrete, and cobbles do little to save nature.
Mowing your garden every week is damaging to the prospects of most wildlife and yet it is an endemic practice in Ireland, the UK and much of Europe. Yet many of the same people, if asked, would claim to care about nature.
Just as you cannot have the butterfly without the caterpillar, there is no biodiversity without a loving and hospitable home for our wildlife.
For most people, including butterfly and moth lovers, the larvae are rarely seen. But in some cases, the larvae are extremely interesting and very beautiful. Here we show a selection of butterfly and moth caterpillars and tell you a little about them.
All photographs J.Harding except Alder moth F. Parnell.
A Cinnabar moth caterpillar on Common Ragwort. This is one example of a highly conspicuous caterpillar and is easily the most reported caterpillar. This larva feeds in groups when younger, and their brash colouring warns predators of their toxicity. The caterpillars absorb toxins from the foodplant which contains pyrrolizidine alkaloids which are fatal to livestock and humans if absorbed in sufficient quantity. This appears to make the larva distasteful too, and birds learn to avoid the caterpillar. Common Ragwort and Marsh Ragwort are native plants, important for pollinators, but the plant should never be allowed to grow in hay meadows where hay is used to feed livestock. The Cinnabar moth controls Common Ragwort, eating the flowers before seed can form.
Next is a green caterpillar, the larva of the Green Hairstreak butterfly. This one is feeding on Bilberry, a bog and heath plant. The larva is well hidden on its foodplants and is very hard to find in the wild. It pupates in summer and the adult emerges the following spring and summer. The larva is stated to be cannibalistic but it has been reared collectively in captivity without any fatalities.
Another green larva, the Cryptic Wood White, relies on camouflage to be undetected by birds. It lies flat against the stems of its foodplant, especially Meadow Vetchling, adding to its blending ability. This caterpillar is also remarkably hard to locate. Eggs are usually laid singly, meaning the larvae are well dispersed, presumably allowing the species to avoid predation. Larvae that blend with their food are typically edible.
Time for something exotic! This is the larva of the Common Swallowtail butterfly on Common Fennell growing against a limestone rubble wall in Gozo, Malta. The butterfly is rarely seen in Ireland but is a possible future colonist. The fleshy protuberance is an organ called the osmeterium, extended when the caterpillar experiences a threat. The organ emits a sour smell of rotting pineapple to deter predators. Strangely, this organ does not appear to be used by the larva in its final growth stage.
The Tussock moths produce wonderfully flamboyant larvae, and the Dark Tussock, a bog moth, is one example. It feeds on heather and sometimes gorse. Its dense covering of bristles must be unappetizing to Meadow Pipits, a bird frequent on bogs.
The Pale Tussock moth caterpillar is more widespread and even showier. This species breeds on birch, oak, apple, hazel, limes, elms, Common Blackthorn and Common Hawthorn. The larva is usually seen in late August and September when it appears on or near the ground when it leaves the tree to pupate among debris on the ground.
The Vapourer moth is another member of Lymantriidae, the tussock moths. In Victorian England, a Vapourer was the name for a braggart or boastful person, and this larva certainly boasts extravagant outline and livery. The larva feeds on willows, Bog-myrtle and the same trees used by the Pale Tussock.
We don’t have the iconic Purple Emperor butterfly in Ireland but we do have the Emperor Moth, a beautiful bogland, heathland, fen, mature dune, and scrubland inhabitant. The newborn larvae are black, resembling miniature Peacock larvae, but colour changes eventually culminate in the form you see here. This species uses a range of foodplants. In Ireland, it has been recorded on birches, Alder Buckthorn, willows, and heathers.
A clouded Yellow on Common Bird’s-foot-trefoil. The butterfly appears in Ireland every year but not in abundance, except in some special years, like 2000. It is very common in Southern Europe, emerging in early April in Tuscany and probably earlier further south.
The Narrow-bordered Bee Hawkmoth is a day flyer, and very popular among nature photographers. The caterpillar feeds on Devil’s-bit Scabious, and its apparently unnecessary purple markings make sense if you see the foodplant, which often contains dark purple blotches on the leaves and purple on the flowering stems. Like the other hawkmoth species, the caterpillar has a tail.
The Lackey moth belongs to the family Lasiocampidae, the Eggar moths. It breeds on a number of trees, especially Common Hawthorn, and is mainly southerly in its occurrence in Ireland. The larvae feed in large groups and bask on webs, which can be large and conspicuous. Like many moths with colourful larvae, the adults are rather cryptic. The adult Lackey is usually straw-coloured and nocturnal.
The Small Eggar is rare in Ireland, despite having common foodplants like Common Hawthorn. This photo was taken in the Burren, near Carran, on open limestone with scattered scrub. It overwinters as a pupa, sometimes for two or three winters before the adult moth emerges. The adult flies early in the year, from January to March.
This is the larva of the Narrow-bordered Five-spot Burnet moth, a black moth with red spots on the forewings’ upper surfaces. The larva feeds on Meadow Vetchling growing in a tall sward, often on damp soils. The moth, both in the larval and adult stage, is easily confused with a much commoner species, the Six-spot Burnet, which is abundant on dunes in summer.
The colourful larva of the Sweet Gale moth belies the subdued, grainy grey adult’s colouring. Oddly, this moth has two generations a year in Ireland but just one in Britain. It feeds on Sea Plantain, Ribwort Plantain, Sea Campion and woody plants like heather.
The caterpillar of one of Ireland’s rarest butterflies, the Pearl-bordered Fritillary, is feeding on Common Dog-violet in the Burren, County Clare. This larva leaps off its foodplant when it wants to bask, landing impressively on its feet. Like many larvae that develop in early spring, it spends long periods basking in the sun on dry vegetation while it digests its food. It also appears to use its basking site as a latrine.
The Knot-grass is another dull moth with a colourful larva. It has a range of foodplants, including Meadowsweet and Devil’s-bit Scabious. This one has coiled into a ring, a typical defensive pose for a disturbed larva.
Like the Pale Tussock larva, the handsome larva of the Alder moth is usually seen when it leaves the foodplant (Alder, birches willows, oaks) to pupate in rotten wood on the ground. Photo by Fionnuala Parnell.
The Dew moth is an orange-yellow black-speckled day and night flyer that can be seen in the Burren in May, June and July. The caterpillar feeds on lichens growing on rocks.
A Comma butterfly caterpillar on Common Nettle. The species include Hops, elms and willows in its diet. Since the larva was first recorded in Ireland on 17th May 2014 in Carlow, the Comma has been recorded breeding in several counties, including Wexford, Wicklow, Meath and Dublin. It has recently been recorded breeding in Irish gardens and appears poised to colonise the entire island.