Wicklow’s Spring Biodiversity Explosion

As April draws to a close we have reached high Spring, and this year has been a superb one. The steady weather conditions and good levels of sunlight have transformed the landscape. The shrubs and trees are beginning to bloom, adding to those of the undergrowth. This year the lilac trees have been early and especially impressive due to the dryness – in wet years the fleshy, fragrant flower-spikes rot rapidly. This year they are the magnificent ornaments they are meant to be.

Lilac blooms - Syringa vulgaris

But the undergrowth is only really getting started. In woodlands, and on the narrow lanes of Wicklow you will find intoxicating seas of Ramsons (Allium ursinum), the wild garlic. Driving along these lanes with the car window rolled down can be something of an aromatic adventure in springtime.

Ramsons or Wild Garlic

The flowering plants depend on sunlight, and in turn the invertebrates, particularly insects, depend on the flowering plants to provide serious energy, in the form of nectar and pollen. Of course, the plants are equally dependent on the insects to fertilise them so there will be more plants, and insects, next year. Away from the trees the Daisy (Bellis perennis) are one of the most important nectar-producing species, supporting every conceiveable pollinating creature, and reaping the rewards. Wild meadows are very important habitats for this reason.

A Speckled Wood butterfly (Pararge aegeria) feeds on one of thousands of daisies in a small meadow.

As the length of days and exposure to sunlight increases the number of plant species in bloom greatly increases, which in turn supports more and more pollen and nectar-dependent organisms.

This, in turn, leads to an increase in predator numbers. One of the most interesting and unusual predators of other insects is the Yellow Dung-Fly. These flies are normally seen perched on cow dung in huge numbers, where they mate, lay eggs, and attack and eat other insects attracted to the dung. However, in spring they feed mostly on pollen, because there is so much of it about, and their prey numbers are still growing. The fly in the photo is covered in pollen, having clearly gorged, probably on daisies.

Yellow Dung-Fly (Scatophaga stercoraria)

Because of predators nectar and pollen-feeders have to be able to defend themselves: in spring you will see many species of bee, all armed with potent stings.

Bombus pascuorum is a distinct bumblebee species with a very long probing tongue, which allows it to fertilise many flowers no other insects can...it is vital to the environment. Here is is seen feeding on dandelion.
Nomada bees are small, solitary species that look very like wasps, but are extremely shy and best seen feeding on apple blossom. They are quite curious and will "people watch".
A female Mining Bee (Andrena haemorrhoa), a solitary species commonly seen in spring, where they build little tunnels in lawns and meadows, with small vocanic-looking cones around them. This species collects pollen on special hairs on its hind legs, as you can see in this photo.

However, many of the bees you will see in Wicklow are not bees at all. Instead of developing toxins, many species of fly have opted to imitate bees, and it is difficult even for naturalists to tell them apart. The trick is to look at the heads: the flies have large round heads with little or no fur, and they have only stubby antennae, whereas bees always have long antennae curling from their heads.

A brilliant white-tailed bumblebee-mimic hover-fly, Volucella bombylans, feeding on Alexanders.
A stunning hover-fly, Leucozona lucorum, also feeding on Alexanders by a roadside.

However, flowers do sometimes get more than they bargained for, slugs will also happily eat pollen, and the entire flowerhead. But only very, very slowly, and very occasionally.

A beautifully-patterned Common Garden Slug (Arion distinctus), feeding on dandelion pollen.

Thanks to the abundance of nectar many insects can take time off to find mates and breed, something that would be impossible to do if they didn’t make a profit when it comes to feeding. The beautiful little Orange-tip butterflies are only with us for about four or five more weeks, so watch out for them in gardens, along roads and flower-filled meadows with good hedgerows. They are now taking the time to find mates and breed, and the sight of a pair of them dancing over hedges is a strong sign you will very soon witness a marvellous event: I saw Orange-tips mating for the first time in my life this week. They are so common at this time of year, it is strange how well they hide their social lives. Maybe they’re marvellous camouflage prevents the casual observer from noticing. However, I’m not a casual observer, so it is rare: if you do witness this event you are one of a lucky few.

A mating pair of Orange-tip butterflies perched on sedge. The male is the right way up.

A Fantastic Voyage into Spring

The air is now filled with wonderful aromas and perfumes from the blossoming trees, bushes and flowers. All along the hedgerows is the heady scent of freshly flowering alexanders, flowering currant and the subtle fragrance of apple blossom wafting from the orchards.

Now there is an excitement of life. The big bumblebees harvest the nectar of the apple blossoms, and the predators hide among the petals to snatch the unwary insects that come to feed.

White-tailed Bumblebee (Bombus lucorum) feeding on apple blossom.
Look closely - this little fly has been captured by a large and superbly camouflaged Flower Crab Spider (Misumena vatia).

Added to the aromas is the subtle and delightful fragrance of gorse (Ulex europaeus), a spiny bush that grows in dense thickets across the hillsides of Wicklow and provides a vital habitat for vast numbers of species. It is also known as Furze or Whin, from which the small bird known as the Whinchat derives its name. The flowers are very popular with small insects, especially pea weevils, the flowers being remarkably like those of peas.

Gorse flowers, complete with tiny weevil.

At this time of year the hedgerows are edged by dense thickets of Alexanders (Smyrnium olusatrum), a hogweed like umbellifer with lovely yellowish-cream flowerheads that provide vital nectar for honeybees, drone flies, ladybirds, and many others. But in April you will see a very peculiar, large black fly hovering above them and the hedgerows, with long legs trailing beneath it. This species is the St. Mark’s Fly (Bibio marci), which is so-called because it usually appears in the sky near St. Mark’s Day, the 25th April. Although excellent fliers, much like hoverflies, they are incredibly ungainly when they land, which is usually only to feed and to mate. Mating pairs are normally found all over the Alexanders, which are like the insect equivalent of dance clubs.

 

St. Mark's Flies hovering above a hedgerow, legs trailing beneath them conspicuously.
St. Mark's Flies mating while perched on Alexanders. The larvae live long lives in the soil and leaf litter and will appear as adults next spring.

However, it is the butterflies that steal most attention in the hedgerows. April and May are the time of the short-lived Orange-tips. The female is extremely beautiful, but upstaged by the male, with his glowing orange wing-tips. Like so many insects, most of their lives are spent as larvae, but most spectacularly for the brief period they are adults. They are among the most difficult butterflies to photograph, of those found in Wicklow.

Female Orange-tip (Anthocaris cardamines) at rest on apple. It is rare to see a female perched with her wings open for any length of time, but if you are patient you increase your chances.
A spectacular male Orange-tip feeding on vetch in a hedgerow.

Although the Orange-tips certainly draw most attention, by sheer force of their colour and presence in numbers at this time of year, they by no means hold a monopoly over colour. Not so common in spring, but equally colourful are the Peacock butterflies, which are especially fond of dandelion flowers. They are a long-lived hibernating species, so many of those that apear in springtime have slightly ragged wings. However, their eye-spot wing-markings sometimes draw attacks from highly territorial breeding birds.

A European Peacock butterfly (Inachis io). Note the torn left hind wingspot...almost certainly made by an attacking bird, possibly a territorial attack or the hallmark of a hunting Swallow.
The hedgerows of a spring lane in the warm April of east Wicklow.

The Undergrowth Comes Alive

The sunlight, and longer days are warming the valleys of Wicklow. The smaller wildlife, on which all others depend, are starting to steal the show. While strolling in a garden or along a village lane you might see a scarlet-coloured fluttering object drop from the sky and out of sight. It might appear a little later, but if not, look on the low-growing foliage for the beautiful and aptly-named Ruby Tiger moth (Phragmatobia fuliginosa), which emerges from its pupal coccoons in April and May, to take to the sky. This species employs bright colouring to warn of distasteful toxins in its body.

Ruby Tiger Moth lying low in a meadow. Beneath the forewings is a searing red underwing only usually discernible when the moth is in flight.

At the other end of the colour spectrum is the Holly Blue butterfly (Celastrina argiolus), a stunning little spring butterfly that loves to bask on wide hedgerow leaves. This butterfly likes woodland glades and narrow laneways, aswell as gardens.

Holly Blue butterfly - you can tell this one is female by the narrow black margins on the outer edges of the forewings: males have much thicker markings, effectively black patches.

If you are very lucky you might even be fortunate enough to see a mating pair. Mating is a quiet and symmetrical affair. The lovers rest, joined by their abdomens, but facing in completely opposite directions. They only move to angle their wings in the sun.

A mating pair of Holly Blues. Behind them is a dangerous-looking, but harmless and extremely handsome Syrphus hoverfly.

However, the sunlit leaves are not necessarily safe places. Predatory invertebrates brazenly wait, motionless in the undergrowth, for unwitting visitors to arrive to provide them with lunch. Crab spiders wait on the leaves, and will soon be hiding among the blossoms.

Flower Crab Spider (Misumena vatia), waiting for prey. Crab Spiders get their names from their habit of grasping prey with their two long pairs of forelegs, while balancing on their two shorter pairs of hind legs, as this one was doing.

However, many small creatures are fortunate enough not to hide on leaves. Your best chance of seeing the Early Thorn moth (Selenia dentaria) is now in April, usually perched on timber door or window frames, and garden sheds. The first generation male, pictured, is perfectly coloured to match dark timber, and dry leaves in the hedgerows.

A male Early Thorn moth perched on a door frame.

An Adventure in the Garden of Ireland