September always sees a reduction in the numbers of moths which come to light as the nights get colder. Underwings predominate with very large numbers of Large Yellow Underwing (Noctua pronuba) and Lunar Underwing (Omphaloscelis lunosa), and smaller numbers of Lesser Yellow Underwing (Noctua comes). The first of these can often be seen during the daytime, particularly near the coast, as resident numbers are swelled by immigrants. The two other species which appear in large numbers at traps are Square Spot Rustic (Xestia xanthorapha) and Setaceous Hebrew Character (Xestia C-nigrum), the former being very variable in colour, but usually identifiable by the large square dark smudge between the reniform and orbicula stigmata.

The smaller numbers of moths being caught in traps allows us to appreciate some of the more attractive species, Beaded Chestnut (Agrochola lychnidis), Frosted Orange (Gortyna flavago) and Rosy Rustic (Hydraecia micacea) being particularly nice ones to catch. Pride of place must, however go to a species which can be found wherever there are mature oak trees nearby, a moth whose name is as beautiful as the stunning colours of a fresh specimen, Merveille du Jour (Dichonia aprilina). At this time of year those of us who use light traps always look at the outside first, as this species prefers to sit on the outside rather than enter the trap.

Another species which is tree dependant is Blair’s Shoulder-knot (Litophane leautieri hesperica), found wherever there are Cupressus leylandii (which probably means everywhere!). First recorded in 1951, this species is now widespread over southern England, and has just been recorded for the first time in Ireland.

Other common species which appear in September are Black Rustic (Aporophyla nigra), Flounced Rustic (Luperina testacea), Canary-shouldered Thorn (Ennomos alniaria) and Dusky Thorn Ennomos fuscantaria). There are also species which can always be seen in small numbers throughout the year, such as Pale Mottled Willow (Caradrina clavipalpis), Angle Shades (Phlogophora meticulosa), Brimstone (Opisthograptis luteolata), Buff-tipped Moth (Phalera bucephala) and Common Wainscot (Mythimna pallens). When the winds are right (from the continent) it is still possible to see a few migrants, such as SilverY (Autographa gamma), Rush Veneer (Nomophylla noctuella) and in daytime, Humming-bird Hawk-moth (Macroglossum stellatarum).