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Moths of the month: August 2017

This is a monthly series illustrating several characteristic moths to look out for in our area. Text and photos by Roy Leverton.

You can also view the other months by selecting the links at the bottom of this page.

   
Square-spot Rustic (R Leverton)

Square-spot Rustic Xestia xanthographa

Late July to late September.

Almost everywhere including gardens.

Ubiquitous and abundant, this noctuid suffers from over-familiarity. Its re-appearance is also an unwelcome sign that the best of the summer is already over, far too soon. Nor does it help that our Scottish examples tend to be particularly dark and dingy, with the characteristic yellow forewing markings often scarcely visible. Nevertheless, we should respect it as a successful species able to thrive in a wide range of habitats and climate.

The caterpillar feeds mainly on grasses, but also on a wide range of low plants. It overwinters while fairly small, then grows rapidly in spring, when it can easily be found by torchlight after dark. Once fully grown in May, it makes a cocoon in the soil but does not actually pupate for perhaps a couple of months.

The adult is hardly ever seen by day and presumably hides low down in the sward. At night it visits nectar sources such as buddleia and ragwort, and is often the most numerous species at sugar or in the moth trap.

Click on the image to enlarge it.


Dioryctria abietell (R Leverton)

Dioryctria abietella

July into September.

Coniferous woodland.

Though a micro, this pyrale is larger than many macro-moths, yet has no English name in common use. Its caterpillar feeds inside the shoots and cones of a wide range of conifers including pine, spruce and larch, but even in appropriate habitat the moth is rarely numerous. It is also considered a partial migrant.

At rest, the narrow forewings overlap and hide the much broader hindwings, creating a very twig-like shape. As with other members of its family, the antennae are laid along the back when the moth is at rest. Its thorax has two tufts of raised scales that help to keep them neatly in place.

Click on the image to enlarge it.


Coxcomb Prominent larva(R Leverton)

Coxcomb Prominent Ptilodon capucina

Larva fully grown August-September.

Deciduous woodland, parkland, scrub.

By August, the caterpillars of many spring and early summer moths that feed on deciduous trees are reaching full growth, hoping to pupate before the leaves wither and fall, or autumn gales dislodge them. Coxcomb Prominent is a relatively frequent find at this time of year, often on rowan in our area.

This is one of the easiest caterpillars to identify because of its distinctive contorted posture, with jaws and six red thoracic legs presented like spines at a would-be attacker; on the tail hump two red warts each bearing a long bristle likewise appear threatening. Whether this display is backed up by unpleasant glandular secretions is unknown. For a relatively low-density species, perhaps bluff alone is enough to deter a young bird that has never encountered one before.

Click on the image to enlarge it.


Annulet (R Leverton)

Annulet Charissa obscurata

Mid July and August.

Rocky coastal cliffs, quarries.

Annulet is a classic example of a species that forms isolated colonies where the adults closely match the local rock on which they rest – from almost white on chalk to various shades of brown or grey according to the geology. Presumably this is caused by the strong selective pressure of visual predation.

Only a handful of colonies are known in our area, though given the dangers of working its favourite habitat (especially at night) others may be overlooked. The example figured is from the Banffshire coast and illustrates its camouflage ability very well. Note how the undulating edges to the forewings and particularly the hindwings help the moth to merge with the substrate by blurring its outline.

Though hard to locate by daytime searching, after dark the adults are strongly attracted to ragwort flowerheads in the vicinity of rocky scree.

Click on the image to enlarge it.


Flounced Rustic (R Leverton)

Flounced Rustic Luperina testacea

August into September.

Sand dunes, arable farmland, road verges.

This is one of many superficially similar brown noctuids that are often confused by beginners, but its stocky build and shaggy thorax, coupled with the late summer flight period, help with its identification despite a wide range of pale or dark colour forms. Once learnt, its jizz is distinctive.

Flounced Rustic prefers light, well-drained soils, where its subterranean caterpillar feeds on the roots of grasses. In the northern half of Scotland it is a mainly an eastern, low ground species, commonest on coastal sandhills, but scarce or absent in the higher, wetter inland and western regions. However, like several other moths with similar habitat requirements, it is numerous on the sandy machair of the Outer Hebrides.

Though hardly ever found by day in any of its stages, after dark the adults are strongly attracted to light, whether that is a moth trap or a kitchen window.

Click on the image to enlarge it.


View other months

January - February

March

April

October

November - December

2008: May | June | July | August | September

2009: May | June | July | August | September

2010: May | June | July | August | September

2011: May | June | July | August | September

2012: May | June | July | August | September

2013: May | June | July | August | September

2014: May | June | July | August | September

2015: May | June | July | August | September

2016: May | June | July | August | September

2017: May | June | July | August

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