Male moths and butterflies often fire blanks but nobody knows why

A few days ago I tweeted about a famous picture of a moth, the Death’s Head Hawk-moth used in the artwork surrounding the 1991 psychological thriller “The Silence of the Lambs”. At first glance, the moth looks genuine, but closer inspection reveals that what is thought of as markings resembling a skull on the moth’s thorax is, in the movie illustration, actually an imprint of a well-known 1951 creation of Salvador Dali and photographer Philippe Halsman.

In that image, In Voluptas Mors, a group of naked women were posed in such a way as to create the illusion of a skull. Of course, this morbid allusion fits perfectly with the theme of a murderer who skins his female victims in the movie. The women are lambs to the slaughter, their fleeces flayed from their bodies by the serial killer and a symbolic moth placed on their tongues to silence them forever.

Although a representation of the Death’s Head Hawk-moth (Acherontia atropos) features in the promotional materials for the film. Fellow science writer Rowan Hooper reminded me that in the movie itself, it is the pupae of a different moth, the Carolina Sphinx Moth (also known as the Tobacco Hawk-moth (Manduca sexta) that feature in the plot. In our chat, I mentioned that I wasn’t particularly interested in moths when that movie was first on release, but he said he was very much interested in Lepidoptera (moths and butterflies) at the time, Indeed, Hooper was specifically working in research trying to figure out something rather odd about Lepidoptera.

It turns out that the males of all Lepidoptera, all 180,000 species of moths and butterflies produce two types of sperm. They make sperm that carry their genetic material, their DNA, in the sperm’s nucleus, so-called eupyrene sperm, but they also make sperm that lack that DNA, apyrene sperm, or parasperm. Indeed, at least half of the sperm are blanks. In one type of swallowtail butterfly, 90 percent of the male’s sperm lack DNA. That percentage is 96 in Manduca sexta. Even more bizarrely, Lepidoptera are the only creatures that do this.

Obviously, the fusion of sperm with egg is fundamentally all about fusing the genetic material from the male with that of the female to fertilise the egg and create offspring from both parents. So, why would males make sperm that contain no genes to pass on and more to the point would be incapable of fertilising the female’s eggs. To cut to the money shot: nobody knows, for sure.

There are hypotheses, of course. It might be that the blank sperm act as some kind of useful filler, inactive biological padding. The blanks perhaps take up the female’s resources somehow while the active sperm do their job. Maybe this precluded further matings with other males ensuring that the first male’s active sperm are the ones that fertilise her eggs. Alternatively, perhaps Lepidoptera females have defences within their reproductive tract to ensure that only the fittest sperm reach their eggs and so the males produce these blanks as decoys (after all blanks would require fewer material resources and energy to produce, if many are going to be wasted). An alternative theory might be that the blank sperm are some kind of nuptial gift for the female, not so much inactive filler as nutrients.

There is evidence that a gene known as Sex-lethal (Sxl) is involved in the production of apyrene sperm in Lepidoptera. A paper in PNAS looked at the activity of this gene in the Silk Moth, Bombyx mori, and found that it was partially responsible for the generation of apyrene sperm. Moreover, the team showed that apyrene sperm have to be present in the male moth’s ejaculate to allow the active eupyrne sperm to travel from the female’s genital opening, the bursa copulatrix, to her spermatheca (where she stores sperm prior to egg fertilisation).

So, while no definitive answer is known for all Lepidoptera that produce eupyrene and apyrene sperm, for the Silk Moth at least it seems that firing blanks is the best way for the active sperm to hit the target.

Hacking the moth trap

I’ve had to hack my moth trap, or more specifically, I’ve had to hack my two moth traps.

The white, plastic vanes are broken on my original moth trap (the collapsible wooden one bought from an ex-mother and cabinet maker friend mentioned here years ago). The UV U-tube also failed in the night a week or so ago, So, having previously also acquired a spare moth trap from yet another friend in the village who is also an ex-mother, I have now hybridised the original box and funnel with the vanes and UV tube from the second trap. The U-tubes were 40 Watts, the linear bulb is just 20 Watts, so will be half the electricity cost on lighting-up sessions (although not as cheap to run as the 1 Watt LepiLED, good success with that on a couple of field trips).

As you can see, the Perspex shoulders of the box have clouded over a lot since I acquired the original trap and I ought to replace those. The point of having a transparent upper is so that plenty of light from the lamp gets into the box so that the moths don’t simply head for the exit hole once they’re in the box. As regular readers will know, the box is filled with egg trays to give the moths somewhere to roost overnight until they’re logged, photographed and safely released the next day.

There are at least seven mothers in our village, although only four of us are currently active, I believe. Three are definitely ex-mothers. I have the old traps of two of them and the third disposed of her trap for ethical reasons, although I think having people trap for scientific purposes is more ethical than not knowing anything about the local moths. We are a big village, very long, flanked by farmland and some trees. So, for the County Moth Recorder, it is useful to have records from across the patch and the area is big enough that individual trapping is very unlikely to disturb moth populations and biology in any significant way.

Beaded Chestnut
Beaded Chestnut hiding on a leaf

Anyway, it’s mid-October and last night was wet but brought in a fair number of moths, more than the previous session with the now-defunct 40W kit: Beaded Chestnut 3, Black Rustic 2, Box-tree Moth 1, Light Brown Apple Moth 4, Lesser Yellow Underwing 1, Large Yellow Underwing 3,
Red-line Quaker 2, Shuttle-shaped Dart 1, Strawberry Tortrix 2, Vine’s Rustic 1, White-point 1.

Black Rustic
Black Rustic

Mothing stats

UPDATE: 29th October 2022 – Finally added December Moth to the list of Lepidoptera I’ve logged and photographed. This was my 463rd moth species, and 64th new species logged in 2022.

December Moth
December Moth, new for me 2022-10-29

One might ostensibly refer to mid-October as the point in the year at which the mothing season is beginning to draw to a close. There are still plenty of autumnal moths to be seen, (various Sallows, Merveille du Jour, Red-line and Yellow-line Quakers, Bricks etc, and then winter moths (Winter Moth, November Moth, December Moth etc) around and a chance of rare migrants but from now on, a cold lighting-up night might give you a blank from here on until mid to late February…it can be a gloomy time for moth-ers, although perhaps not quite as gloomy as it is for the moth-ers we know as butterfliers.

One of several Convolvulus Hawk-moths that nectared on my garden tobacco plants
One of several Convolvulus Hawk-moths that nectared on my garden tobacco plants in the summer of 2022

Anyway, I’ve done sone totting up from my records. Just in case you’re interested in the details of this year’s mothing here in Cottenham and with a couple of off-site sessions. I have counted about 7500 moths of some 318 species in 200 lighting-up sessions so far this year. I’ve been mothing since July 2018 and have recorded 460 species in that time. 60 of those species were new to me this year alone.

Light Crimson Underwing was drawn to the LepiLED in the New Forest session in 2022
Light Crimson Underwing was drawn to the LepiLED in the New Forest session in 2022

In the previous three seasons, the new-for-me numbers were in the 30s. However, a mothing session in the New Forest, one in Dorset, and success with garden tobacco plants here, bumped up the NFMs, that and my being more diligent in logging micro moths. If I remember rightly, I did far fewer sessions in 2019, but had some nights with several hundred moths and my total that year was 12500 moths of almost 300 species.

Male Oak Eggar seen in the summer while butterflying along Devil's Dyke, Cambridgeshire in 2022
Male Oak Eggar seen in the summer while butterflying along Devil’s Dyke, Cambridgeshire in 2022

Another new moth, Clancy’s Rustic – Caradrina kadenii

TL:DR – I’ve been mothing since July 2018. In 2022, I recorded almost 50 new species in my garden. It was just 37 in 2021, and 30 in 2020.


As the year rolls by, the number of new moth species a novice moth-er with 3-4 years experience is likely to see on any given night declines with the arrival of autumn. All the moths I saw in my first season were pretty much new-for-me (NFM), about 127 species. In 2019, lighting up for a longer period, I recorded 125 NFM. 2020 wasn’t a great year not many moths at all after an unseasonably warm and sunny pre-Spring and I recorded just 30 NFM. Similarly, 37 NFM in 2021. However, despite odd weather again in 2022, I’ve recorded 49 NFM in the garden and a dozen with the LepiLED in the New Forest.

Among those NFM species was the fabulous and rather rare Convolvulus Hawk-moth. Several (perhaps 5) have turned up in our garden, perhaps drawn to the nectar of the tobacco plants we grew especially for them.

There are, of course, plenty of autumnal moths and maybe a clutch of those have not been ticked. Then, there are the recent additions to the British List, such as Clancy’s Rustic. Clancy’s Rustic Caradrina kadenii
(Freyer, [1836]) which was first reported by Sean Clancy in Kent in 2002.

One turned up in the garden last night, looking quite fresh. I thought I’d seen one before in 2020 but when I double-checked my records it turned out to have been the rather similar-looking Pale Mottled Willow, which is quite common in my garden. So, at last I can tick one of the rarest of the rare moths, Clancy’s Rustic as NFM.

Clancy's Rustic moth
Clancy’s Rustic

 

 

Hairstreak butterflies

There are so many “hairstreak” butterflies around the world, members of the Theclinae, with lots of tribes. Indeed, nobody knows for sure how many of these delightful little creatures adorn our world. In the UK, we have just five of them as native species, and they’re quite rare and tend to live and breed only in small pockets.

In 2021, I saw my first Green, Purple, and White-letter Hairstreaks with a little bit of guidance from some butterflyers I’ve mentioned before. In 2022, I made a concerted effort to try and find at least one of the two others that are not too far to drive from home – the Black Hairstreak. I may have glimpsed it in 2021, but I definitely saw and photographed it in a place called Monks Wood one of its rare habitats.

The fifth the Brown Hairstreak has a flying season August-September and we tried to spot it on our final day on the edge of the New Forest where there was plenty of fresh blackthorn (the larval foodplant) but with no luck.  A possible trip to nearer Suffolk might have been productive, but it’s probably too late in the year for it now, so Brown HS is going to be a target there for me in 2023 instead.

In the meantime, you can catch up with some of the 50 butterflies and 460 moths I’ve photographed and videoed for Reels on the Sciencebase Instagram

The Convolvulus second coming

UPDATE: A rather battered Connie turned up on the night of 8th September. That’s three nights we’ve seen the species in the garden, it’s possible there were two on the first occasion (27 August), but just one on 2nd September, and just one last night. Although there’s no way of knowing for sure, there may have been others on those nights and other nights, all may well have been attracted by the scent of the garden tobacco plants we grew specifically to attract this species. All were subsequently drawn to the UV lure.

Usually, one relies on Attenborough and his marvellous army of photographers and researchers to bring the dramatic natural world closer to home. At a push Spring Watch and its ilk can give you a slightly less educational fix with their low-level narrative and low-level cameras. But, nature impinges on even the most urbane of urban gardens at times.

Indeed, we see various butterflies in the garden on warm and sunny summer days – Comma, Painted Lady, Red Admiral, Peacock, Whites (Large and Small), Holly Blue, very occasionally Common Blue and Small Copper, even (once) Marbled White. Hummingbird Hawk-moths turn up during the day and with a little luring, Emperor Moth and various Clearwings. I’ve listed the birds elsewhere on Sciencebase.com, we’ve ticked 30 species in the garden or over it. At night, there are hedgehogs and the Common Frogs are active in and around the pond. Speaking of which various dragonflies and damselflies around the pond and their larvae in it. Also at night, Pipistrelle bats circulating, hunting for moths…oh…moths.

As regular readers will know, surely…I light up with an ultraviolet “lemp” to attract moths and record and photograph them. 459 species so far in four years of mothing. One of the most intriguing and, I feel, exciting visitors was the Convolvulus Hawk-moth. It nectared on Nicotiana (garden tobacco plants) planted specifically to give it something to eat should it turn up. As you know, it did and then again this evening. It’s a huge beast, three or four inches across, it makes a lot of noise whirring and whirling around the garden and clacking into walls and plant pots in between bouts of unfurling its enormous proboscis to feed.

A second, possibly third, one appeared to nectar and then was distracted by the lemp. I got some video of the Convolvulus Hawk-moth just before it dived into the trap. But, I couldn’t leave it there to fester overnight so I lifted the lid to let it out. It soured away into the night sky, like a whirring wraith in a pink and black stripey mohair rollneck. Who needs Sir David, when you’ve got plain David? Hah!

Let’s twist again with the Garden Rose Tortrix

Having written about one of the bigger moths we see in the UK, Connie, the migrant Convolvulus Hawk-moth, it only seems fair to give a mention to a micro, as opposed to macro moth. So, here’s the Garden Rose Tortrix.

Garden Rose Tortrix
Garden Rose Tortrix

Now, the macro versus micro label may well have been historically about size. The larger moths being macro, the smaller moths being micro, as you might imagine, but there are so many enormous micro moths and so many tiny macro moths in the world that this really doesn’t hold. In fact, the division is one of evolutionary history, the micro moths being a much older grouping.

The micro grouping includes all of the butterflies, which are essentially just a family of micro moths. The only physiological difference between what British English thinks of as butterflies and moths is that the butterflies cannot unhook their forewings from their hindwings. That’s it. Asking what’s the difference between a butterfly and a moth is like asking what’s the difference between a ladybird and a beetle, or a dog and a mammal…

Anyway, back to today’s micro. This tiny two-toned moth is known as a Garden Rose Tortrix, Acleris variegana. It is one of about 11000 worldwide moths that are members of the tortrix family, the Tortricidae. They’re so-called because their larvae roll themselves up in a leaf to pupate and metamorphose into the winged, adult. The word tortrix has the same etymology as the word torque, the word for a twisting force – torquere, meaning to twist.

Egging on Toadflax Brocade caterpillars

As regular Sciencebase readers will know by now, this once workaholic science writer is now a highly dedicated mother. As in I am an enthusiastic amateur Lepidopterist. A moth-er, like a bird-er, birder, someone keen to see, observe, understand, and perhaps photograph the subject. This year and last, I’ve also been a bit more focused on being a butterflyer too.

Toadflax Brocade larva with foodplant, Purple Toadflax
Toadflax Brocade larva with one of its foodplants, Purple Toadflax

Anyway, part of being a mother usually involves finding ways to see moths. Commonly that involves some kind of lure – a pheromone bung or an ultraviolet (or other) light. And, again, as you will know, I’ve got several lures for enticing moths for observation and the inevitable photoshoot. At the time of writing, I’ve lured and photographed about 450 moths of the 2600 species found in the UK.

Adult Toadflax Brocade
Adult Toadflax Brocade moth

The standard approach to nocturnal mothing is to have a box above which a bright light or bright UV source is suspended, often above a funnel or vent. Moths are drawn to the lamp, like moths to a flame but without the fire risk. They might circulate a while and will often spiral or dive into the funnel opening or the vent and then find it rather difficult to navigate their way out again. A good mother will have pre-filled the trap with lots of empty cardboard egg trays. The trapped moths will settle down in the nooks and crannies of these trays for the night ready to be logged and photographed in the morning.

Moth-trap lamps do not only attract moths, beetles, flies, wasps, hornets, worms, snails, slugs, all kinds of creatures will be drawn. But, it also seems so will the larvae of moths, the caterpillars. A few mornings back, while logging the night’s moth haul (before release into undergrowth away from the garden) I found in one of the egg trays, a couple of caterpillars, larvae of the Toadflax Brocade moth. They must have wriggled all the way from the other side of the garden, about 12 metres where there is a patch of Purple Toadflax or perhaps 15 metres from the Common Toadflax (Butter-and-Eggs) patch to the patio whereupon the moth trap sits on lighting-up nights.

Toadflax Brocade cocoon
Toadflax Brocade in its cardboard cocoon

The two larvae were pupating and using tiny fragments of the cardboard egg tray to make their protective cocoon. One had made a good start and was almost completely enclosed ready for its metamorphosis, the other had a long way to go and so was still very exposed and so obviously a Toadflax Brocade larva. I’ve relocated the egg tray to an under-cover bench outside the garden shed where hopefully the two will finish their transformation and emerge at some point in 2023 as adult moths. I’ll keep you informed as to their progress if anything changes in the meantime.

Convolvulus Hawk-moth in Cambridge

TL:DR – The Convolvulus Hawk-moth is an infrequent visitor to British gardens, but they do occasionally turn up, having crossed the channel, and there is evidence of breeding here, but not over-wintering yet. Several were attracted to Nicotiana I grew especially for them.


UPDATE: 8 Sep 2024 Finally, annother Connie, no Nicotiana, just turned up, hung around the wisteria, flew off.

UPDATE: 1 Sep 2022 Another arrived in the garden tonight less than a week after the first, it nectared on the still blooming Nicotiana before diving into the actinic moth trap. I lifted the lid to let it out and it soured away into the night sky, like a whirring wraith in a pink and black stripey mohair rollneck.

The Convolvulus Hawk-moth, named for its larval food plant convolvulus (bindweed) and its hawk-like appearance, is a relatively rare visitor to the UK from mainland Europe.

Convolvulus Hawk-moth, Agrius convolvuli
Convolvulus Hawk-moth, Agrius convolvuli

The books usually say it migrates rarely and will be seen only in the South West of England if it does, but it has appeared elsewhere, often carried in on the same weather as other migrants, such as the Hummingbird Hawk-moth. There’s also the likelihood of the offspring of Spring migrants appearing as adults in the late summer.

Convolvulus Hawk-moth, Agrius convolvuli

The species’ wingspan can be 85 to 120 millimetres, as big as the British Privet Hawk-moth and with those pink and black stripes it’s almost like a close cousin.

The Convolvulus Hawk-moth likes to nectar on tobacco plants and ginger lilies among other flowers and I have been growing the former in our back garden since I started mothing in the hope of seeing a Convolvulus. After our trip to the New Forest with the LepiLED,* I reverted to my trusty 40W actinic trap next to the tobacco plants for the first evening lighting up back home. Within 20 minutes or so I could hear a whirring, humming insect near the plants and with a torch caught site of it with its huge compound eyes glowing like embers in the air. It did not stay long and flew off over neighbouring gardens. I mused on it being another migrant, perhaps a Striped Hawk-moth of which there had been many recent reports across East Anglia and the southern counties, but this moth was bigger, a lot bigger.

I could confirm the Convolvulus ID when it (presumably the same insect) made another appearance in the garden five minutes later. There have been several reports of Convolvulus in the county this year already, so this wasn’t the first.

The one in our garden, sucked a little nectar from the flowers of the garden tobacco plants before heading for the UV lamp and diving into the trap. I quickly took the trap indoors and got setup for a photoshoot. I snapped a few closeups of this beautiful moth before releasing it back to the night air.

As you can see from my photos it has some of the character of the Privet Hawk-moth, another member of the Sphingidae (what the Americans call Sphinx moths as opposed to Hawk-moths). Wingspan can be between 85 and 120mm, this one, I estimated was about 110mm across.

Convolvulus Hawk-moth
Convolvulus Hawk-moth, with 50mm battery for scale

Convolvulus often appears alongside other migrants. It has been a particularly good summer for the distant, much smaller cousin, the Hummingbird Hawk-moth, as I’ve mentioned here and on Twitter, Facebook, and Instagram. The Striped Hawk-moth has been reported widely, and I am still hoping that one will turn up here, it would be a grand end to our holiday period if it were to join the Convolvulus in making a late Summer appearance.

*The holiday mothing was limited to lighting up with the LepiLED and logging the Lepidoptera in the morning, most of our adventures were out and about in the local countryside and on the coast. The more general photos from our trip will appear in good time, but right now I am focused on the Convolvulus.

Mothing in the New Forest

FINAL UPDATE: Back home, checked through the records. 12 species I’d not seen before, at least two of which are usually confined to the South coast and hinterland.

Lesser Swallow Prominent
Lesser Swallow Prominent

The list of moths I’d not photographed before our New Forest 2022 trip is as follows: Black Arches, Chequered Fruit-tree Tortrix, Cydia amplana, Dusky Thorn, Hedge Rustic, Lesser Swallow Prominent, Lesser Treble Bar, Light Crimson Underwing, Plain Wave, Dark-barred Twin-spot Carpet, Rosy Footman, Six-striped Rustic.

August Thorn
Dusky Thorn

Records now dispatched to Hampshire County Moth Recorder, Mike Wall.

UPDATE: Seventh Night: A warm and dry night, 60 or so moths of 26 species, including one final new for me: Small Square-spot.

UPDATE: Sixth Night. Started off rather dry and balmy, I’d lit up before we left the holiday house for the pub and there was quite a lot of European Hornets hanging around when we got back well after dark. I also caught sight of a Rosy Footman (new for me), a Light Emerald, and a few veneers. But, it started raining heavily during the night.

Light Crimson Underwing, Catocala promissa
Light Crimson Underwing, Catocala promissa

By Thursday morning there was quite a lot of water in the trap and the egg cartons were soaked, there were still 40 moths of 23 species, with two or three escapees that eluded identification. Once again a few clipped wings present suggesting that the local Robins had been dining at the trap after dawn too.

Rosy Footman
Rosy Footman

I managed to fish out the Rosy Footman and another new for me, Light Crimson Underwing (this completes the set of Catocala underwings I’ve photographed). There’s a short video clip of the LCUW on the Sciencebase Instagram, with Going to the Chapel as the background music for good reason given the scientific names of these large underwing moths.

Lesser Treble Bar
Lesser Treble Bar, possibly just Treble Bar, but for the inner angulare marking, didn’t check male’s claspers

UPDATE: Fifth night. Cool, but not wet. About six moths of 23 species. Some new for the week, like Yellow Shell, Straw Underwing, Mother of Pearl, and Canary-shouldered Thorn. Also, new for me Dark-barred Twin-spot Carpet (very worn, most likely Dark-barred than Red though) and Hedge Rustic. Numerous clipped wings in the trap and bird droppings on the top from avian activity.

Hedge Rustic
Hedge Rustic

UPDATE: Fourth night. Drizzly night, around 70 moths of 30 species. Probably overlooked a couple but also had my first Dusky Thorn and Lesser Swallow Prominent, numerous Small Bloo-vein, lots of Flounced Rustic and Agriphila tristella again, and at least a dozen Red-legged Shield Bug.

UPDATE: Third night numbers were down a lot, but there was still a Buff Footman, another Jersey Tiger, Oak Hook-tip, and a Plain Wave (NFM) and various others (mainly Agriphila tristella and Flounced Rustic). Added some video of the Jersey Tiger to my Instagram with a snippet of appropriate ABBA.

Plain Wave
Plain Wave

UPDATE: Second night of lighting up, quite a lot more moths around 40-50, including Black Arches (3, NFM), Jersey Tiger (2), Light Emerald (6), Maiden’s Blush, also a European Hornet.

Two male Black Arches
Two of three male Black Arches to the LepiLED, second night

First night off-site with the LepiLED and a portable Robinson-type moth trap was in North Poulner in the New Forest. We ate fairly late but there were Pipistrelle bats circling the trees in the garden overlooking the valley long before dusk felel.

Chequered Fruit-tree Tortrix
Chequered Fruit-tree Tortrix

I lit up with the trap right under an oak tree, I had high hopes. Numbers weren’t huge, but there were a couple of species I had not seen before – Six-striped Rustic (Xestia sexstrigata, one of the many noctuid, or owlet moths) and Chequered Fruit-tree Tortrix (Pandemis corylana). The latter is also known as the Hazel Tortrix Moth, the Filbert Tortricid or the Barred Fruit-tree moth and sits within the Tortricidae family.

Six-striped Rustic
Six-striped Rustic

Full list for the first lit-up night was: Brimstone, Chequered Fruit-tree Tortrix (NFM), Chrysoteuchia culmella (6), Flame Shoulder, Lesser Broad-bordered Yellow Underwing (2), Light Emerald (3),  Maiden’s Blush, Rosie Rustic, Six-striped Rustic (2, NFM).

North Poulner Valley
Lin Brook valley from North Poulner

Just to note, when I got up in the middle of the night and took a breath of fresh air, as it were, there was a fox trotting slowly past the moth trap in the relative dark, I don’t think it even saw me standing there, certainly didn’t seem perturbed.

I didn’t have my usual macro kit and “studio” with me, so just basic record shots of the new moths taken with my phone camera or non-macro SLR lens. Note to self: take macro lens and tripod and LED staging kit and flashgun on next trip or regret it!

Cydia amplana
Cydia amplana
Dark-barred Twin-spot Carpet
Very worn Dark-barred Twin-spot Carpet