Category: Biology

TL:DR – Moths, Lepidoptera, are an incredibly diverse group of insects with some very diverse behaviour. There are some 180,000 known species worldwide with about 18000 of those known as butterflies in the English language, but butterflies are just a class of moth.

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There is quite a diversity of behaviour among the moths you see in your trap. The various Yellow Underwings almost all flap wildly around inside until the settle down, but if you disturb them they will flap again, flashing their yellow hindwings.

Others are more passive once they have settled down they stay settled down unless disturbed and will generally avoid gripping on to anything other than the original surface on which they landed, Turnip moth is a case in point it seems. But, others will grab on to an offered paintbrush or piece of leaf and happily clamber aboard to be photographed, Angles Shades, for instance, were happy to do this.

Agitate some moths and if they’re not quite warm enough they will sit still but vibrate their wings, revving their engines as it were before taking flight, I’ve watched this with Flounced Rustic, Straw Underwing, Setaceous Hebrew Character, and the Elephant Hawk-moth, which oscillates audibly.

Many of them will, if disturbed, will have a quick flap before landing on their backs and playing dead. If disturbed again they will flap and fly, if they can. I have observed this intriguing behaviour many times in the last few weeks since beginning my mothing career. Most recently, with the nominate form of The Sallow (Cirrhia icteritia), which I’d gently coerced into a jar to photograph and which ended up on its back staring at me. It quickly flipped back over and took flight into the safety of the shrubbery.

Behaviour that was investigated scientifically not too long ago is even more fascinating than any I have seen in the trap or indeed elsewhere. Most moth species have some form of camouflage that allows them to hide on their favoured vegetation. Apparently, the aforementioned Elephant Hawk-moth likes fuchsia bushes and given how the moth looks and the form of that plant’s flowers, you can see why. The Peppered Moth is said to have evolved to cope with soot-covered trees so that during the Industrial Revolution they became much, much darker and better camouflaged on sooty surfaces. This industrial evolution is most likely #DeceivedWisdom given that this species actually roosts on the underside of leaves where predators  would not see them anyway.

Another species investigated recently shows an incredible ability to adjust its position on a tree bark to make itself pretty much completely invisible to putative predators. One has to wonder, how does the moth know what it looks like from above to do this? I can imagine that there are two ways it might be able to carry out this feat. Perhaps the most sophisticated is that its brain has some kind of “map” of how it looks and the moth shuffles around on a surface until the surface matches how it perceives it looks from above.

A second simpler explanation, which occurred to me is that in fluttering its wings gently it can see the shadow beneath them of where the pattern changes and can then simply look to see or feel whether its pattern matches up with the bark surface on which it finds itself. You can read the research here and here.

I contacted the research team to see how and if their work in this areas has progressed and to ask whether my possible explanation for the behaviour had been investigated. This is what the Prof, Piotr Jablonski, had to say:

We have thought along similar lines but did not do any experiments...We thought the by raising and lowering its wings, the moth may compare the colour and/or pattern on its wingtips (visible when raising them) with the colour or pattern of the bark around the moth. This would require changing the colour of the wingtips (probably visible to some moths - but not all - during the wing-raising behaviour) and for it to be able to control the change of colour of the wing area that is not visible. Maybe another student can pick up on this soon...Changku Kang graduated a few years ago.

One other aspect of moth behaviour that has intrigued people for centuries is why moths are drawn to a flame or other light source. The argument is that they use the moon to navigate at night and candles and other artificial light sources confuse them. I don’t think this is true. I have my own theory, which I have discussed here.

Regular visitors to the Sciencebase site and associated social media have probably spotted the leps (Lepidoptera, the butterflies and moths), that have somewhat usurped the previous 18 months of bird photography, although that is still ongoing.

If you haven’t, what have you been looking at, then? Anyway, I was almost set to clean up the borrowed actinic light moth trap and return it to my friend who so kindly lent it to me on 24 July and endowed me with a new addiction.

Red-green Carpet (Chloroclysta siterata)

The reason? Well, there hadn’t really been much new for a while and I was starting to believe that our garden setting is not quite good enough for the moths. I persisted, however, and having had a dearth of new species this last week was rewarded on my return from C5 the band rehearsals last night with several I had not seen before as well as some old favourites.

Lunar Underwing (Omphaloscelis lunosa)The new ones included Lunar Underwing, Red-green Carpet and Black Rustic, and the oldies, but goodies were the various Yellow Underwings (Lesser, Large, Broad-bordered), Flounced Rustic, Gold Triangle, Willow Beauty, Brimstone, Common Wainscot, Vine’s Rustic, Shuttle-shaped Dart, Sallow, and several others. You can see the 100+moths I’ve identified and photographed in my Leps gallery on Imaging Storm.

Encouragement from the mothing community, especially from Rob, Brian, Samantha, Leonard, Matthew, Karen, Mandy, Ben, Jade (who told me Lunar UW was just around the corner), Mark, and others, particularly on the UK moths Flying Tonight Facebook group. And, of course, Mrs Sciencebase who was not so keen initially, but has taken a flight of fancy of late, a lep of faith you might say.

 

Well, after the heady days of late July and August with dozens of different moths coming to the actinic light trap that I borrowed, numbers of species have diminished. The chilly and occasionally damp evenings here in VC29 mean there is less nocturnal lepidopteran activity overall, although there always seems to be a good number of Large Yellow Underwings, Vine’s Rustics, and one or two Setaceous Hebrew Characters in the trap by morning. And, usually, there is the one oddity that keeps me lighting up just for the treat of a new species.

There was a Large Ranunculus a couple of nights ago and a hint of a big, dark Hawk-moth that rattled around in the dark among our shrubbery but didn’t get caught in the trap. It may well have been a Red Underwing or an Old Lady, I didn’t get a good look, but I hold out hope that it was actually a Convolvulus Hawk-moth, and if it warms up again, it may well return. [Had to wait until September 2022!)

Anyway, this morning there was a small dark species on the egg boxes, speckly but sooty black to my bleary eye. It had much more apparent creamy yellow markings once I got the photo up on my screen. Unfortunately, I didn’t get a particularly sharp photo, which is a shame.

It turns out to be a Waved Black Parascotia fuliginaria. It’s unusual in that its resting posture (wing position) is more like the moths known as Geometers (so-called because their caterpillars appear to measure out the earth, inch-worms, they’re often called). The waved black is actually a member of the Erebidae within the huge superfamily known as owlets, the Noctuidae.

Admin and master moth-er Leonard C on the Moths Flying Tonight UK facebook group points out that this species is a fungus feeder (the caterpillars also eat rotting wood) and “will certainly be the star of your catch”, while another admin Mark M told me he was very envious of the find and that for his county, Devon (specifically, VC3), there has only been one specimen recorded since 1995. The nocturnal adults purportedly fly June to August, so interesting that there’s one mid-September.

The Sallow (Cirrhia icteritia) is a Noctuid moth (Xyleninae). I’ve seen a couple of them in the actinic trap over the last few days. It’s a common species in the UK although if you spot one you might be confused by the appearance of another of the same species that does not have the same colouration. It flies in September-October and is attracted to light and sugar solutions (it has feeding mouth parts, unlike many other adult moths). Initially, the larvae (caterpillars) feed on the catkins of the sallow (more often known as willow trees, these days), hence the moth’s common name.

I videoed the specimen pictured above, briefly while it did its warmup exercises ready to take flight.

This is another Sallow specimen, note the rather different colouration from the first