Wednesday, 10 September 2014

Large Yellow Underwing - Noctua pronuba

One of the most common visitors to the light trap I have put out in the garden over the past month has been the Large Yellow Under-wing. One morning I counted 25 hiding among the egg boxes, all clinging on determedly, and difficult to displace. 



According to the UK Butterfly Conservation in the report "The State of Britains Larger Moths 2013" the incidence of N. pronuba has increased by 186% during the period of 1968-2007 (1). The distribution map from the NBN gateway shows how widely distributed it is.



This is a fairly large moth with a wing span up to 60mm. At rest it's not the most spectacular of moths, with a base colour of brown, and few distinguishing markings besides the kidney spots on its wings. However when it flies there's a flash of colour as the forewings spread out and expose the bright orange/yellow colours of the rear wings. As soon as it comes to rest the rear wings are folded away and hidden once more. They rest during the day, but will flash their bright hindwings if disturbed. This display may be designed to surprise and scare-off predators by the sudden flash of colour.


Moth migration has thrown up a number of interesting questions relating to the navigation challenges that they face during different climactic conditions. It has long been proposed that moths navigate according to the position of he moon. However, what about periods when there is cloud cover and the moon is not visible, a situation not uncommon in the UK. Research has shown that moths are able to use the earths magnetic field as a navigation guide. 
In one of the studies moths were placed into a cage on an overcast night, and reversed the earth's magnetic field (3). When this happened the moths realigned themselves according to the new position of the magnetic field.  How insects and animals are able to determine magnetic variations amazes me - mainly because I just don't know how it's done.

Another study by Chapman et al (4) showed that moths are able to select favourable high-altitude winds to help them travel the often long distances involved in moth migrations. The study used entomological radar (no idea what this is!)  tans found that moths were able to increase the distance travelled by up to 40%. Not a bad trick some a small thing that livess for less than a year.


The larval stage of the Large Yellow Underwing Moth is one of the pests known as a cutworm. E.A. Bowles mentioned their destructive habits in My Garden in Spring, the first in his trilogy of books about his garden in Middlesex. He suggested hunting for them by lamplight to keep them from damaging "the tender, juicy buds" of his beloved early-flowering Irises. Accidental introduction of N. pronuba into the US may constitute a major pest threat to commercial crops (5). The larvae develop between September and April above ground feeding on the stems and leaves of grasses and other plants, sometimes grazing them off at ground level. When disturbed the caterpillar adopts a 'c'-shape and this one was about 35mm in length, but they can be up to 50mm long.




References:
1: Fox, R. et al. (2013) The State of Britain's Larger Moths 2013. Butterfly Conservation. http://butterfly-conservation.org/files/1.state-of-britains-larger-moths-2013-report.pdf
2: NBN gateway. https://data.nbn.org.uk/Taxa/NBNSYS0000006193/Grid_Map. Accessed 2014-09-10.
3: Baker, R.R. And Maher, J. G. (1982). Magnetic compass sense in the large yellow underwing moth, Noctua pronuba. Animal Behaviour. 30(2): 543-8. 
4: Chapman,J.W. Et al (2010) flight orientation behaviours promote optimal migration trajectories in high-flying insects. Science. 327(5966): 682-5
5: Bechinski,E.J., Smith,L.J. And Merickel,F.W. (2009) Large Yellow Underwing: A new cutworm in Idaho. university of Idaho. http://www.cals.uidaho.edu/edcomm/pdf/CIS/CIS1172.pdf.



Sunday, 7 September 2014

Caddisfly - Halesus radiatus

Before owning a moth light trap I had not really considered caddis flies as being a frequent visitor to the garden. But over the last few months I found a number skulking among the egg boxes as I empty the light trap in the mornings. Now I struggle enough trying to identify the moths that I catch and release, but caddis flies are even more of a challenge, as they do not seem to attract the attention of the publishing world resulting in a dearth of accessible field guides. There are over 6000 species that have been described worldwide. Of which 199 have been recorded in Britain, but only 3 in Ireland (1). I think that this chap who I found in the light trap a couple of weekends ago is Halesus radiatus, but I'm open to corrections.


Caddis Flies are superficially like a moth, and are a distant relative in the evolutionary sense,  but instead of scales on the wings, Caddisflies have a fine coating of hairs. It is this coating of hairs that gives this group of invertebrates it's name Trichoptera, meaning hairy wings. I think I've said this in another post, but as I get older I forget these things, and it's always worth repeating yourself - unless your wife or daughter are in earshot. It seems that caddisfies dont develop a wide range of colours unless it's brown! 



The larval stage provides the English name of Caddisfly. This is thought to derive from Elizabeth street hawkers called caddis men. The Middle English word caddice, means a woollen braid, ribbon, or tape. Caddice men used to displays these wares by pinning them on their coats. The aquatic larvae makes protective cases from materials picked up in the habitat, including  leaves, tiny sticks, sand and gravel. But not all caddisfly larvae makes cases, but all have the ability to make silk threads. I've not looked for any caddisfly larvae, but there may be some in the small pond we have, and it may be an idea to have a look. There is an interesting and accessible description of the life cycle of the caddis fly on the Fresh Water and Recorders Scheme website (2).


1: Nature Spot. http://www.naturespot.org.uk/taxonomy/term/19486. (Accessed 2014-09-08).
2: Fresh Water San Recorders Scheme. http://rasp.freshwaterlife.org/recorders/publications_resources/how_to/caddis/life-cycle.html. (Accessed 2014-09-08)

Wednesday, 3 September 2014

Rosy Rustic Moth - Hydraecia micacea

I was able to put the moth trap out again on Sunday evening, hampered previously by the awful weather and being away. Sunday evening was mild and dry, but there was a very light drizzle on Monday morning. So I wasn't setting much hope for a large or varied haul. But as. I started taking out the egg boxes I kept on turning up 21 Large Yellow Underwings, 4 Lesser Yeollow Underwings, a single Double Striped Pug (Gymnoscelis rufifasciata, a Setaceous Hebrew Charcter (Xestia c-nigrum), and a rather non-descript, well at least to me, Rosy Rustic (Hydraecia micacea). More about the others another time, but I have to admit to being intrigued by the name of the Rosy Rustic.


As you can see it's not the most colourful of moths with a uniform brown base colour. Even the kidney marks on there wings don't stand out very much. This fairly bland marking and colouration meant it took me a while to identify it.

It has a single generation and flies from August through to October. The eggs don't hatch but over winter as an egg. The larva start appearing from April to early August. Feeds at first in the stem of the foodplant and then later on the roots. When the larva is ready it pupates underground without a cocoon (1). It's a UK resident and the distribution map from the NBN Gateway shows that it can be found throughout the British Isles (2).



Despite being a rather bland looking moth it has been identified as a potential economic pest for some crops (3,4). That said there isn't a great deal on the internet about it. But my garden is safe, no potatos and no hops, except for the ones that are already bottled.



1: Waring, P. And Townsend, M. (2011) Field Guide to the Moths of Great Britain and Ireland. British Wildlife Publishing.
2: NBN Gateway. https://data.nbn.org.uk/Taxa/NBNSYS0000006466/Grid_Map. Retrieved 2014-09-03.
3: French et al (1973) Biology, Damage and Control of Rosy Rustic Moth, Hydraecia micacea (Esp.), on Hop. Plant Pathology. 22(2): 58-64.

4: Rings, R.W. And Letzler, E.W. (1982) Two newly detected noctuids (Hydraecia immanis and Hydraecia micacea) of potential economic importance in Ohio. Ohio J. Of Science. 82(5): 299-302.

Monday, 18 August 2014

Cinnamon Sedge - Limnephilus lunatus.

The light trap came up with a number of new discoveries the other weekend. One of which stumped me for a while. I was convinced it was a micro moth, but the legs were very hairy and didn't quite fit. Neither did the wings. Well thanks to iSpot I was put straight. It's not a moth, but a Caddisfly. I'm not very good at this! But that said this chap, Limnephilus lunatus is quite attractive, also known as the Cinnamon Sedge. The 'lumatus' comes from the crescent shape on the edge of the wings. It is a well known species, especially among anglers. The larva doesn't use sand or other hard materials for building its case, it uses plant materials only. Most of the information I could find on L lunatus came from angling websites.


Caddis flies belong to the Trichoptera, and have been known to fishermen since the advent of fly-fishing and to the entomological for a longer time. Mouffet the author of the first English book on entomology (the 'Theatrum Insectorum') writes in 1658 of the great variety of 'cados worms' to be found in rivers and streams. The name possibly arises from the ancient name for a travelling cloth salesmen who pinned samples of their wares to their coat, they were known as 'cadice men' and it is possible the name 'Caddis fly' is a reference to the cases many Caddis-fly larvae build from bits of debris. The Latin name 'Trichoptera' comes from the Greek 'Trichos' = a hair and 'Pteron' = a wing, meaning hairy winged which is a good description of the adult or imago forms.  In fact Caddis flies are closely related to Lepidotera, and so I don't feel so bad at getting it so wrong.


There are about 7 000 named species world wide of which over 400 occur in Europe and about 190 in Britain. Fossil Caddis flies have been found as far back as the Cretaceous , and possibly from the Jurassic. 


Limnephilus lunatus is on of the few caddis flies which may be a pest. The numbers of larvae in Water Cress Beds may become enormous! That won't be a problem for the tiny pond we have in the garden, but water cress would be welcome. I wonder what's in the fridge?

Sunday, 20 July 2014

Bee Moth - Aphomia sociella

The other week I found a small moth in the light trap, and I had a little difficulty in finding an identification. It turns out I was being my usual stupid self, and had missed the obvious candidate. The temporary mystery moth turned out to be a Bee Moth, Aphomia sociella. It is also known as the Wax Moth, but this can cause confusion with another species,  Galleria mellonella. So for now we'll just continue to call it the Bee Moth. Now this little chap has quite an interesting life cycle.



Bee moths are not very large. And the males and females are different. Females are 33 mm long, have olive-grey forewings with pinkish central area and a large and a small black spots. Males are 35 mm long, have more contrasting colours on their forewings, mainly whitish and brown, with a zigzagging line over the middle.  I think from this description that my visitor on this occasion was a female.


The adult moths are nocturnal and can be attracted to light, and my light trap on this occasion proves this. Bee Moths fly from June to August. The after mating, the females
search suitable host nests and lay up to 100 eggs there. The hosts in this case include wasps and bumble bees. Females prefer to lay their eggs in aerial, exposed nests such as those of the Median Wasp Dolichovespula media , or in nests made up on walls or in nest boxes by the Red-tailed Bumblebee Bombus lapidarius . The nests built close to or under the ground such as those of the German Wasp Vespula germanica  or the Buff-tailed Bumblebee Bombus terrestris  are less sought-after.


The young larvae move quickly and protect
themselves by spinning a strong silk. They grow eating nest materials, stored food, their host’s larvae dejections and other wastes.

Older larvae also eat young bumblebee or was larvae. Caterpillars are very active digging tunnels in the combs and spinning silken webs very dense and difficult to penetrate. The last stage caterpillars move out of the host’s nests and spin long, tough cocoons in communal masses often between planks of wood or narrow gaps between two adjacent
surfaces. These are very difficult to remove and the webbing has the consistence of soft cloth. The Bee Moths

overwinter as larvae in these structures, then in the spring they pupate to emerge as adults at the beginning of summer.






All of this from one little moth. The Nurturing Nature website provides an intriguing description of what happens when a bee nest is infested with Bee Moth larvae: http://nurturing-nature.co.uk/wildlife-garden-videos/bumblebees-and-wax-moths-the-silent-but-deadly-killers-must-see-video-2/.


Although a common moth, the distribution recorded via the NBN Gateway seems to be rather sporadic. I can only assume that there may be some under recording.

Buff Arches

The light trap popped up with a real cracker this weekend when I uncovered a Buff Arches (Habrosyne pyritoides) toward the bottom. The colours and markings are superb. I think is my new favourite.


It has one generation with a flight season from Late June through to early August. The larva feed on Brambles, which we have some growing in the hedge, but it has also been reported to feed on raspberry in captivity. And we have raspberry and cultivated blackberry in the veg patch.



The NBN (National Biodiversity Network) Gateway distribution map shows that Buff Arches is fairly common in the southern part of the UK (1).

1: https://data.nbn.org.uk/Taxa/NBNSYS0000005725/Grid_Map
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Friday, 27 June 2014

Failed Blackbird Nest

I've been away for a few days and the boss has sent me a photo of an empty nest. Almost certainly the blackbird nest I blogged about a week ago is now abandoned, not from disturbance but more probably from predation as the nest is empty. Who the predator was is unknown. Unlikely to be a cat as the nest is difficult to get to and doesn't seem to be damaged. Possibly magpies or jackdaws, both of which are in the garden. Maybe even a squirrel, but I've not seen a grey squirrel for some time now.