Hawkmoths by day and night
Two species of hawkmoth briefly cross paths in their search for nectar, as summer days fade to night
On a fine, still summer evening, in a garden in the south-west of England, a purple thistle is in full bloom. The numerous florets that make up the flowerheads are rich in nectar, attracting a plethora of insects to feed. As dusk falls, a hummingbird hawkmoth can be seen hovering over each flowerhead. It sucks up the nectar with its long tongue, before moving rapidly onto the next flower, its wings a blur. Finally, it has enough stored energy to see it through the night. As the light begins to fade, it heads off to find a safe place to roost, among dense foliage. As it flies off, an equally fascinating relative emerges, for dusk marks the start of the day for this moth, not the end. The elephant hawkmoth is, like most moths, nocturnal in its habits, taking to the wing as night begins. Thus, the lives of these two insects briefly intersect. If this did not happen, they would never meet, for one has evolved to be diurnal, while the other is mostly nocturnal. Another major difference is that the elephant hawkmoth is resident in Britain, whereas the hummingbird hawkmoth is a seasonal migrant. It arrives here each spring and summer in ever-increasing numbers as summers get warmer. The hummingbird hawkmoth is far scarcer and less widespread than the elephant hawkmoth. Its daytime lifestyle, however, means it is seen more frequently.
The hummingbird hawkmoth’s name derives from its apparent similarities to a hummingbird. In a process known as convergent evolution, the two unrelated species have developed similar traits to meet similar environments. This member of the hawkmoth family has evolved a body shape, wing movements and flight action that are almost identical to its avian counterpart, even down to the humming noise made by the wings. It has evolved to fill a niche as an aerial nectar feeder. It is a buffish-orange creature, with grey forewings, orange hindwings, a black-and-white chequered body and a band across the tail. These are even similar colours and patterns to those of some hummingbirds. The wings beat very rapidly, up to 70-80 times a second, giving the impression of a blur to anyone watching. The insect even has what appears to be a face and beak. The former is a series of markings on the head, the latter, the thin proboscis which it uses to obtain nectar. Both bird and moth feed in the same way, by hovering in front of a flower while beating their wings to stay in position. Hummingbird hawkmoths have a wingspan of 2-2¼in (5-6cm), not far short of the size of the smallest species of hummingbird. But there is a big difference. Hummingbirds have only one pair of wings, whereas hawkmoths have two, their forewings and hindwings. These work in rotation to keep the insect aloft, and allow them to manoeuvre even better than the actual hummingbird.
They feed on a wide range of common wild and garden plants. These include honeysuckle, lady’s bedstraw, red valerian and phlox. They prefer those with plenty of nectar and a long calyx, the collection of sepals, which their proboscis enables them to reach more easily than other insects. They are creatures of habit, often flying around in a regular circuit, visiting the same plants again and again.
The first hummingbird hawkmoths of the year are usually seen in south-western or southern counties of England in early May. They can arrive as early as April in fine springs, following southerly winds. These strong-flying insects have come all the way from Spain, Portugal, or North Africa. Some continue much further. In Britain, they have been recorded as far north as Orkney and Shetland. They prefer warm, sunny daytime weather, but will also fly at dawn and dusk, and even during light rain. They have excellent colour vision, which is also very sharp, to enable them to fix on a particular flower while hovering to feed. Hummingbird hawkmoths are long lived compared to other moths, with an adult lifespan of two to three months. After mating, the females lay up to 200 spherical eggs, which measure just 1mm across, from May onwards. Each is laid on a separate plant. They are pale green in colour, mimicking the buds of their main host plant, lady’s bedstraw. This helps them avoid the attention of predators such as birds. Other host plants include hedge bedstraw, wild madder, and red valerian. The eggs hatch between six and eight days after laying. The larvae begin to feed avidly, so they can grow as quickly as possible. When they hatch out, the tiny larvae are yellow, but they soon turn green, with pale and dark horizontal stripes along the body and a blue ‘horn’ with a yellow tip. They use these bright colours and oddly shaped head parts to scare off potential predators, such as songbirds. Approximately three weeks after hatching, now approximately 2½in (6cm) long, they pupate. The pupa drops to the ground, where its pale brown colour enables it to be disguised among the leaf litter. Months later, in mid or late autumn, the pupa hatches into the adult hummingbird hawkmoth. This new generation then seeks out a sheltered spot to hibernate for the winter. It may be in a hole in a wall or tree, or sometimes in an outbuilding, such
“Lovely in dye and fan, A-tremble in shimmering grace, A moth from her winter swoon Uplifts her face:” Walter de la Mare, ‘The Moth’
as a shed or garage. However, in Britain, the winter climate is usually too cold for them to survive.
The elephant hawkmoth leads a very different lifestyle to its cousin, being both nocturnal and resident. It is found throughout lowland Britain and Ireland, especially in large rural gardens, parks and woodland edges. Bright golden-olive in hue, with vivid pink streaks across the body and wings, they are one of the most striking of all Britain’s insects. These colours and patterns appear obvious when the insect is seen in isolation, but they provide surprisingly good camouflage when it is hiding among foliage. Here, the pink streaks help break up its outline. Elephant hawkmoths have triangular-shaped wings, with a wingspan of 1¾-2¾in (4½-7cm), and a broad body, tapering to the tip of the abdomen. The name comes not from the appearance of the adult, but from the larva. These are greyish-brown, and sport a proboscis that looks superficially like an elephant’s trunk. Two large false ‘eyes’ on the sides of its head accentuate this, and give it a snake-like appearance. When threatened by a predator, such as a bird, the 3in (7.5cm) long caterpillar swells up and waves its head in the air. This usually has the desired effect of frightening off the attacker. In Britain, adult elephant hawkmoths are usually seen from May to July. They emerge from their hiding places among plant foliage at dusk to feed on nectar-rich plants. They have very good night vision, with light-sensitive cells in their eyes. These enable them to discriminate between different coloured flowers, when it would otherwise be too dark for them to do so. Their preference is for tubular, nectar-rich flowers, such as those of honeysuckle and willowherbs. Eggs are laid on a variety of plants, including fuchsias, lady’s bedstraw and especially rosebay willowherb. The caterpillars emerge from July onwards, and can be seen until September. When the weather begins to turn cooler in the autumn, the caterpillars pupate. They spend the winter in this form, hiding in shallow soil, or in low vegetation, before emerging as adults the following spring.
Hovering above a thistle, a hummingbird hawkmoth sucks up nectar and moisture through its long proboscis, which is made up of two concave tubes hooked together. When not in use, the proboscis, which is nearly as long as the moth’s body, is coiled up like a garden hose.
A hummingbird hawkmoth caterpillar, with its yellowtipped blue horn. The caterpillars tend to be green when first hatched, turning darker as they grow and moult the skin which no longer fits. The chequered body and grey forewings of the hummingbird hawkmoth. Its orange hindwings are only evident in flight.
When startled, the elephant hawkmoth caterpillar draws its trunk into its foremost body segment. This posture resembles a snake with a large head and four large eye-like patches. › The greenish-gold body of the elephant hawkmoth is punctuated by shocking pink stripes, which act as camouflage on many surfaces.