Adventures in Mothing

I’ve found something new to bore my family with! The last month or so has given me the first chance to really make use of my (relatively) new light trap to start learning about a whole group of organisms I previously knew nothing about.  I now know just enough to realise how little I know but am amazed by the number and diversity of moths turning up in a smallish garden in a housing estate in a Durham village. Having read Michael McCarthy’s book The Moth Snowstorm, I am well aware that my previous lack of knowledge makes me susceptible to ‘shifting baseline syndrome’ – I have no idea how many moths I might have found in the past.  However, it seems worth celebrating the abundance and diversity which remains. 

I’m intrigued to know how much the way I garden contributes to that diversity but sadly have no baseline study of my own. I know that most of the moths I find in the light trap will not have been living as larvae in my garden but maybe some have? I wish I’d taken regular photos to show how our garden has changed and matured over the years!  When we moved into our brand new house more than 20 years ago, with nothing but mud beyond the patio, almost the first thing I did was to plant climbers and young fruit trees along the fences and seed the lawn to provide a base for the large climbing frame which dominated the garden for many years.  We were lucky to have mature willow and whitebeam trees growing at the end of the garden (actually that is why we chose this plot) and I screened off a corner below the willow with shrubs to give space for den building.  One memorable summer the children decided to mine for clay beneath the willow as part of some entrepreneurial scheme, excavating a sizeable pit which has only slowly filled itself in.  Another autumn someone emptied a whole bag of slightly mouldy conkers here and for a number of years we had a burgeoning forest of leggy Horse Chestnut saplings, most of which have had to be cut back before they took over the garden completely.

I have never had a very diligent approach to gardening, in particular lawn maintenance, preferring to encourage the patch of sky-blue Germander Speedwell which appeared beneath the Whitebeam to mowing stripes in the lawn. The crops which thrive best in my allotment are those which benefit from benign neglect. In the last three years, as I’ve read and thought more about biodiversity loss and the role gardens can have in countering this, I’ve been more actively neglectful of the ‘lawn’, participating in No Mow May (actually, No Mow Summer), raising wildflower plugs from seeds to plant out in the grass and encouraging plants which have arrived by themselves – see my No Mow May blog for photos. Many of these plants are larval food plants for moths.
One of the biggest insights from starting to learn to identify moths has been realising that I have no idea where to start. The Field Guide to the Moths of Great Britain and Ireland by Paul Waring and Martin Townsend I was given with the light trap is somewhat daunting for a beginner. It details the features of all 896 species of macro-moths which occur in the British Isles, along with the habitats in which they are found and their distribution. The thick tome is a salutary reminder of what it must feel like to be a beginner botanist handed a copy of Francis Rose’s Wildflower Key! With practise, as a botanist, you soon start to spot the tell-tale characteristics of particular plant families. Noting features such as flower shape, number of petals and form of reproductive structures can let you turn quickly to the correct part of the book, rather than wading through a long general key. In the same way, families of moths share characteristics such as wing shape, resting posture and body form but these are still quite opaque to me. Sometimes apparently similar moths turn out to come from completely different families. The book does come with a comprehensive set of excellent plates by Richard Lewington but just flicking through these till I find something which seems to match the moth in front of me feels too much like what I tell my students off for!
I’m learning slowly what to look for; does the moth hold its wings out horizontally, vertically or at an angle against the body when at rest? Are the forewings broadly triangular in shape or much longer than they are wide? Is the moth’s body elongated or stout? Are the antennae slim or feathery? I soon decided the only way to start getting to grips with the features which define a moth family was to start my own species list, arranged in the same way as the species are listed in the field guide so here is an introduction to some of what I’ve found in the garden light trap so far.
Moths from the smaller families at the start of the book are amongst the largest and the most distinctive and I have to admit to looking first for these when I open my light trap. So far I have found a Ghost moth from the Hepialidae (Swift moths), a Drinker moth from the Lasiocampidae (Eggar and Lappet moths), and Poplar Hawk-moths from the Sphingidae (Hawk-moths).

Clockwise from top left: Ghost moth, Hepialus humuli; Drinker moth, Euthrix potatoria, resting and preparing to fly; Poplar hawk moth, Laothoe populi

There are over 300 species of moth in the family Geometridae, which come next in the field guide, so it is not surprising that they are well represented in my trap; to date I’ve identified around 20 species. They are quite varied in morphology but tend to have broad, triangular forewings and light, slender bodies, for low energy flight. Many of the adult moths have functional tongues which allow them to drink moisture but they don’t particularly rely on refuelling frequently with nectar. The caterpillars of these moths are the ‘loopers’ which sometimes catch on your hair as you walk through woodland – they have no legs in the central part of the body and move by drawing the back end up to the three pairs of legs at the head end. The Geometridae include Wave moths, Carpet moths, Magpie and Peppered moths and Thorn moths.

Geometridae, clockwise from top left: Riband Wave, Idaea aversata; July Highflyer, Hydriomena furcate; Common Carpet, Epirrhoe galiata; Barred red, Hylaea fasciaria; Peppered, Biston Betularia; Scalloped Oak, Crocallis elinguaria; Light Emerald, Campaea margaritaria; Early Thorn, Selenia dentaria and centre, Magpie moth, Abraxas grossulariata.

The Erebidae include some of the biggest and most flamboyant moths (Tigers and Ermines) as well as the much smaller and less impressive Footmen and Snouts. It’s not clear from the field guide what they have in common to be lumped together and some were previously regarded as distinct families or sub-families of another large family. I’m assuming the similarities are genetic and evolutionary, rather than morphological!

Erebidae, clockwise from top left: Buff ermine, Spilosoma lutea; White Satin, Leucoma salicis; Garden Tiger, Arctia caja; Common footman, Eilema lurideola; Pinion-streaked Snout, Schrankia costaestrigalis; Ruby Tiger; Phragmatobia fuliginosa borealis

The Noctuidinae is the largest family of macromoths in the British Isles, with some 370 species, and this is again reflected in the diverse species I find in my light trap. The field guide describes these moths as mostly medium-sized, stout-bodied and brown, with forewings longer than they are wide. They are specialised for powerful, manoeuvrable flight, mostly at night and the family includes most of the British moths which migrate long distances. To do this, they need to refuel so, unlike many moths, the adults feed on nectar, tree sap or aphid honeydew. Noctuidinae tend to rest with their forewings at least slightly overlapping to form a tent over the body.

Noctuidae, clockwise from top left: Burnished Brass, Diachrysia chrysitis f. aurea; Antler, Cerapteryx graminis; Heart and Dart, Agrotis exclamationis; Double Square-spot, Xestia Triangulum; Bright-line Brown-eye, Lacanobia oleracea; Dark spectacle, Abrostola triplasia and Plain Golden Y, Autographa jota

Although these moths are, undoubtedly, mostly brown, they are far from uniform in appearance and the iridescent scales of the Burnished Brass make it one of the most attractive of all moths, to my mind.
My species list is growing fast (at least 55 to date) but is very far from a complete record of what has been in the trap. Many moths fly away before I get a chance to look at them and I’m not even attempting to identify the smallest ones. I have much to learn, too, about why particular moths turn up in my garden, how far they might have travelled, whether the caterpillars are present too and what kind of things affect moth abundance from one night to the next. During the extremely hot weather of mid-July there were many times more moths in the trap than after this week’s cooler nights. So much to consider….

3 comments

  1. Really interesting and inspiring Heather. Can you share a picture of your light trip please? Do you (temporarily) capture them or just observe them as they come close? Xx

    • I’ll WhatsApp you some pics Vicky – you basically set it up at dusk and the moths fall though a big funnel into a box where you put old egg boxes for them to roost in. Then in the morning you open it up and look to see what’s inside!

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