Insect extravaganza

Late summer is arguably the most diverse and interesting time of the year when it comes to insects in our area. Long days, warm temperatures and an abundance of flowers and fruits provide the ingredients for an explosion of of invertebrate life of all kinds, each cashing in on nature’s seasonal bounty. It’s an exciting time for the naturalist, not least because you’re never quite sure what will come your way next.

This I found out last weekend, while doing some gardening on our plot adjacent to the northern boundary of the Reserve. As I was minding my own business, a colossal insect buzzed right by me, making a sound not unlike a Lancaster bomber. Ridiculously, for a six-foot outdoorsman, my first instinct was to dive for cover. After picking myself up again (and having a surreptitious glance around to check that none of the neighbours had seen me), I went to identify the beast in question, which had headed straight for a pile of uncut firewood. And what a beast it was.

Giant Wood-wasp

Meet the Giant Wood-wasp, alternatively known by the older (and more descriptive) name of Horntail. This colossus of the insect kingdom, sitting here on our wood pile, measured more than 50mm (over 2 inches in old money) from the tips of its yellow antennae to the end of its fearsome-looking ‘stinger’. However, this isn’t actually a stinger at all; it instead houses an ovipositor – a mechanism by which the female wasp lays her eggs into the timber of dying or recently-felled trees. And for confusion’s sake, it’s not even a true wasp, but rather one of the sawflies – close relatives of the true wasps and bees, all of which share the order Hymenoptera.

Sure enough, closer inspection showed that our Horntail – a female, hence the horn tail – was busy laying eggs into a Sitka spruce log, drilling into the timber with her long, needle-fine ovipositor. All the time, her wings were vibrating rapidly, and apparently this helps to drive the ovipositor into the wood with a rapid sawing motion. This explains why the wings look blurred in the photos!

Giant Wood-wasp egg-laying

Her work done, she climbed her way to the top of the log pile and took flight once more, bearing a remarkable resemblance in flight to a Hornet as she headed westwards inland. Where she had come from was a mystery, but it’s likely that this species – which specialises on softwoods such as pine and spruce – will currently be making a good living off the storm-damaged trees that still litter the countryside following the wild weather of the preceding winter. In any case, the log in question has now been marked with an ‘X’ in ink, and will be set aside rather than turned into firewood. Then, perhaps in three years or so – for this is the length of time the larvae remain in the timber – we might have a hatch of Giant Wood-wasps of our very own.

Note the ovipositor at work

While we were thrilled with the Wood-wasp encounter, it’s easy to see how some folk get a bit freaked by such a large and dangerous-looking insect (even though, in reality, it’s a completely harmless beast). Butterflies, however, are one group of insects that seem to meet with almost universal approval, their bold colours a joy to see, brightening up a summer’s day. This week we’ve noticed the first newly-hatched Small Tortoiseshells emerging, a perennial and easily-identifiable favourite. These will be the offspring of last summer’s generation, which overwintered as adults and emerged in early spring. These newly minted individuals are so much smarter than the often scruffy and careworn ones we see earlier in the year.

A mint Small Tortoiseshell

Out in the grasslands, meanwhile, you might be lucky enough to catch a glimpse of a Common Blue butterfly skipping by. These are the only blue butterfly to occur at Forvie, so no ID challenges here. Seen at rest, these are truly gorgeous insects, with the blue changing its hue depending on the light and the angle you’re viewing from. Sometimes azure, sometimes purplish, sometimes dusky – but always stunning to look at.

Male Common Blue at rest

Moths are a big part of the scene on the Reserve just now, and though they’re often viewed with disdain compared with butterflies, this is somewhat unfair. Of course, most people only ever see moths bashing against a lit window at night, or occasionally happen upon one of the day-flying ones, many of which look unremarkable compared with butterflies. But there are notable exceptions. Take the two common day-fliers below: the Common Heath is understated but rather beautiful seen close up (and check out those feathery antennae). But the Six-spot Burnet is altogether more showy, in the manner of a butterfly.

Common Heath moth – a day-flier
Six-spot Burnet – likewise

Of course, many moth species are night-flying, but as we’ve demonstrated before, they can be captured using a light trap, thereby allowing us an insight into an otherwise unseen world. At our recent Fun Day, the moth trap was a remarkably popular attraction, and consequently last week’s Marvellous Moths event was very well subscribed. The night before the event, we operated not one, not two, but three light traps, all in different locations (the grassland behind the Forvie Centre; the Alder plantation alongside the track to the Reserve; and your author’s garden in Collieston). This, we hoped, would produce a range of species with different habitat preferences, giving our visitors plenty of variety to look at. And we weren’t disappointed! Here are some of the highlights.

Lempke’s Gold Spot
Beautiful Golden Y
Garden Tiger close-up
Burnished Brass – check out that metallic sheen
Lesser Broad-bordered Yellow Underwing (catchy, huh?)

The diversity of moths is absolutely astonishing, with around 1,500 species occurring in Scotland (as compared with just 37 species of butterfly). Yes, separating some of the tricky (usually brown and cryptic) species is difficult for the beginner, and can even be tough for the experts at times! And their names can be a challenge too – try saying Lesser Broad-bordered Yellow Underwing with a mouthful of crisps. But what beauty and variety there is to be found – and that’s the case wherever you are, from urban gardens to National Nature Reserves. Following the excitement of the event, we resolved once again to build ourselves a light trap for use at home – maybe this time we’ll actually get around to it!

The excitement of ‘mothing’

Of course, there’s plenty of interest in the insect world outside of the Lepidoptera (butterflies and moths). One of the more obvious groups to the casual observer are the bumblebees. Contrary to popular belief, there’s not just one type of bumblebee, but a range of different species. Look a little more closely and you will soon start to notice differences between the bees that visit your garden flowers. Some wear the classic black-and-yellow stripes, such as this White-tailed Bumblebee…

White-tail feeding on Wild Thyme

…while others carry a very different appearance, such as the teddy-bear-like Common Carder Bumblebee.

Common Carder on Knapweed

The examples above are both common, widespread and easily identified, and are among the most obvious of the 19 species found in Scotland. So it’s well worth having a closer look at the bumblebees in your garden, or out on the Reserve, to see if you can spot the differences and start to recognise the individual species.

Other insect groups are much larger though. It’s reckoned that there are roughly 2,600 species of beetle in Scotland – now that’s a lot of differences to try and learn. While this seems daunting for the budding naturalist, you can make a bit of headway with the more distinctive-looking ones. And this is where the internet is heaven-sent, as there are numerous apps and websites available to help with species ID. For instance, after a very quick bit of research, we were able to determine that this fabulous metallic-looking beast was the leaf beetle Chrysolina polita. And that was with no prior knowledge of the subject! All you need is an eye for detail, and to be curious.

Chrysolina polita – surely deserves a common name!

Sometimes though, keen naturalist that I am, I’m forced to admit defeat. Some species groups present such a minefield of identification problems that they just have to be left alone. Recently, this ichneumon wasp turned up on our window at home, and looked (to my eyes) distinctive enough to be identified. However, upon recoursing to my usual internet trawl, I was dismayed to learn that the UK has approximately 2,500 species of ichneumon to choose from, and that many of them essentially look exactly the same as one another. Oh dear.

‘Ichneumon sp’!

Anyway, regardless of whether you can name every species that crosses your path (and I don’t know anybody who can), when all’s said and done it doesn’t really matter. More important is to recognise that there’s a huge diversity of insect life out there, a hidden world that most of us never take the time to acknowledge and appreciate. But there’s never a better time to start than right now, in the vibrant, buzzing days of late summer.