Saturday, 29 September 2012

Garden Snail Parade

Since I started this blog, I have been surprised by the diversity of land snails about in the city. As I have managed to get most of them on white background, I decided to write a post and display them all together.

Moss snail, Lauria cylindracea, a tiny, easily overlooked species which gives birth to live offspring. 

Garden Snails, Helix aspersa (=Cantareus aspersus), unashamedly mate in the middle of your garden  path throwing darts at each other. 
Girdled Snails, Hygromia cinctella, like walls. An introduced species since 1950, still expanding across Europe from the Mediterranean.
Kentish snail, Monacha cantiana prefers drier places. This species, introduced in the UK during Roman times, is a very common snail in my local Wildlife Garden. They can be darker with pale speckling.
Glass Snails, Oxychilus draparnaudi, are carnivorous snails that have caused havoc on native snails when introduced outside the UK.
Amber Snails, Succinea putris usually live in very damp places, but can be also found away from water. They cannot completely retract their bodies inside their shells.

Brown Lipped Snails, Cepaea nemoralis are very polymorphic in colour and pattern.You might be lucky to have these beauties in the garden.  

Have you noticed all the snails are facing to the right? This is because most (90%) of all snail species have right-handed shells (dextral). Occasionally a left-handed individuals appear in populations of right handed snails. These face a problem when trying to mate, as the genital opening will face away from most other snails in the population. The genetics of shell handedness has been elucidated in some species and appears to be determined by mutations in a single gene, but the left-handedness trait is expressed not in the mutant, but in the resulting offspring.

More information
Visit the Molluscs posts in Bugblog.
Terrestrial Mollusc Tool. A wonderful resource for US molluscs. Contains also lots of info on introduced European slugs and snails.

Saturday, 22 September 2012

Angle Shades moth

This Angle Shades moth, Phlogophora meticulosa, caught the attention of my 8 yr old while it rested on dark moss. Angle Shades are very distinctive moths, as they rest with their wings folded lengthways, but the disruptive wing colour pattern and their crumpled appearance makes them difficult to spot when they rest on dry leaves. I moved it to the fallen leaves of Virginia Creeper, which match the moth's subtle colours, to take its portrait. The species belongs to a group of large noctuid moths - which include the Lesser Yellow Underwing and the silver Y - that are regular migrants to the UK from continental Europe, although the Angle Shades is able to overwinter here as well.

Monday, 17 September 2012

Fresh lilac blues

The flying season of the Common Blue butterfly, Polyommatus icarus, is coming to an end. The adult generation will die off in the next few weeks and caterpillars will overwinter and pupate in spring to emerge at the beginning of June. The Common Blue has two generations in the south of the UK, but only one in Scotland. In between, a second generation might be attempted depending on weather conditions. These individuals look so fresh I find it difficult to believe they have been around since June.
 Although I have only seen this butterfly rarely in my garden, it is a regular of the local wildlife garden, where there is abundant Bird's Foot Trefoil, the primary larval food plants. I photographed this pair of Common blues there on the 7th of September. The male's upper wings are an iridescent violet-blue (above), while the female has only a dusting of blue scales over brown.
Female Common Blue
Male Common Blue

Saturday, 15 September 2012

Are male false widow spiders ant mimics?

An adult male Common False Widow spider, Steatoda bipunctata, barely half a cm in size, scuttled across the kitchen floor yesterday, most likely in search of receptive females. As most spiders, males look quite different from females, but these do look peculiar due to their very large palps, which they carry together while they walk. It immediately reminded me of a garden ant. I googled 'ant mimic Steatoda' and got nowhere, and my reference books also drew a blank, although they noted the relatively large male palps. How can you tell if a spider is an ant mimic (a myrmecomorph)? Sometimes it is so hard to tell them apart the myrmecomorph even tricks ants themselves - which the spider can then predate easily. Other myrmecomorphs are content to trick birds or other common spider predators which find ants distasteful, and the resemblance then might not be so striking on close inspection. There are several recognised ant-mimic spiders in the UK, which are likely to have evolved to resemble the ubiquitous garden ant Lasius niger, a small (4-5 mm), dark brown to black ant (see previous post on Micaria pulicaria). In that post I referred to a list of morphological features that ant-mimics are likely to have evolved, devised by Paula Cushing, so I can check if my candidate ant mimic male Steatoda bipunctata meets them:

1. Body shape: three body segments. Spiders have two body segments so ant-mimics must evoke the three body segments of an ant (head, thorax, abdomen) The large palps of male Steatoda bipunctata, carried raised and together, appear to make the role of an 'ant head'. Check!
2. Three pairs of legs and one pair of antennae. I need to carry more observations on live individuals to assess how the front legs are carried, as ant mimics carry them forward and often raised.
3. Petiole or 'waist' of the ant. My spider has a strong constriction at the end of the cephalothorax reminiscent of the 'waist' between the thorax and the abdomen of the ant. Check!
4. Mandibles. Pointed palps, but not an obvious feafure of Lasius niger.
5. Pair of compound eyes. No clearly mimicked, but also not a very distinctive feature of L. niger.
6. Sting. Not normally visible in Lasius niger.
7. Thin body and legs. Check!
8. Shiny surface. Very shiny, waxy looking. Check!
9. Segmented abdomen.  Abdomen with bands that reflect light as the tergites in an ant abdomen, with a similar pubescence. Check!

Not bad, a clear 5 out of 9 ant-mimic features clearly by this species, and I must add that something missing from the list are the general size and colour, which in this case also fit the garden ant. That the male does resemble an ant more than the female could be explained by the fact that he is likely to be exposed to predation while he moves in search of females - who sit on their webs and would be unlikely to gain much from resembling an ant.
What do you think? 
Ant Lasius niger tending aphid
Top view of male Steatoda bipunctata

A stop for a comma

Before today, I had only seen a Comma butterfly, Polygonia c-album, this year, but today I saw four. Two of them nectared on a large flowering ivy. This fresh individual sat on a rowan leaf and groomed its tongue after feeding on a budlleia in my garden. Although the bright orange upperside of the Comma is striking, I love the mimetic, subtle tones of its underwings. Their dark brown tones and the scalloped edges make them resemble a withered leaf, and there is a strong contrast with their white legs and the neat C on its hindwing. This one offered a wonderful photo opportunity with with ripe rowan berries as a background.

Tuesday, 11 September 2012

Spider scrum

I bet it is hard to find a higher leg density than in a freshly born ball of spiderlings. These 30 or so Pholcus phalangioides spiderlings hatched last night on the ceiling of my outside toilet, about 240 legs in just a few cubic millimeters. In the morning they were still clutching each other and their empty egg sac. By today's afternoon, they had arranged themselves under the vigilant eye of mum as in my previous post.

Monday, 10 September 2012

And now, ladies and gentlemen, spider sex!

ResearchBlogging.orgI have seen spider courting behaviour on a few occasions, but the courtship was either too slow for me to watch the end of it, or the affair ended when the female captured the male and had him for lunch. Yesterday I was luckier, as I watched the common spider, Linyphia triangularis sequence of courtship and copulation. Let me warn you: spider sex is weird. Male spiders produce their sperm in testes inside their abdomen and insemination is internal, but instead of penises, they use their pedipalps - or palps - as an intromitent organ. This requires that before copulation takes place, the male transfers semen dropplets to reservoirs in his palps. This is a delicate operations: the male spins a tiny web and deposits a drop of semen onto it, then picking it up with the palps. Spider palps are a pair of modified appendages at the side of his mouth. In females and immature males, palps look like small legs. Once the male spider moults into adulthood, the palps appear fully developed, with a bulbous end and often a darker shade of colour than in the female. Palps have complex and diverse shapes, depending of the species, and are often used to identify male spiders. Palps have an additional function in some spiders, produce visual signal, as in jumping spiders and wolf spiders.
 Liniphya triangularis lives hanging belly up from its hammock-like web and courtship occurs at the end of summer, right after the female undergoes her final moult. The pair of Liniphia were actually mating when I saw them in a web in a Sedum plant, but a Siver Y moth disturbed them and they separated. The male then walked its way slowly across the web in search of the female. When he touched her, she moved a little further away, he then followed, touching her lightly every now and then. Once he faced her, she stayed still and accepted him by lowering her body at an angle, so that he could reach the underside of her abdomen, near the cephalothorax, where her genital opening is. He proceeded to insert one palp into her genital opening at a time, then the palp swelled as it locked with the females genital opening (above shot), and he removed it, appeared to lick it and then inserted the other palp. This was repeated on for quite a while as the male may need more than 100 intromissions to inseminate the female with two dropplets of sperm! The female was quite cooperative troughout and there were no signs of agression. She seems to touch the male's head with her chelicerae. Today they were still sharing the same web. Female normally only accepts a single male for copulation if he has completed sperm transfer, but this species has an alternative mating tactic in which smaller males interfere with mating and try and mate with the female (more here).
 I took two videos of the behaviour. The first one is a short sequence of the copulation itself, it the second, the pair, which has been disturbed, are separated and the male finds the female again and proceeds to carry on mating.

More information
Weldingh, Ditte Louise, Søren Toft, &; Ole Næsbye Larsen (2011). Mating duration and sperm precedence in the spider Linyphia triangularis Journal of Ethology, 61, 143-152 DOI: 10.1007/s10164-010-0237-x

Sunday, 9 September 2012

Bug heads

Dead heading is one of the rules of gardening, isn't it? You are told to remove the faded flowers so that seeds don't form, as they extract lots of energy from the plant. But what will you miss? you want to look at seedheads. In a walk around my local wildlife garden I found that meadow cranesbill's seedheads were busy with shieldbugs of several species, feeding on them. Among the bugs there were some striking black and red ones (above), which I had never seen before, they were very flighty and the light conditions were not right, but I managed some shots. Upon looking into the British Bugs site I identified them as Corizus hyoscyami a species that during the last decade has expanded throughout England from a few coastal locations in Wales, another species that, according to the NBN gateway, wasn't known to have crossed the Humber before.
Corizus hyoscyami feeding on developing cranesbill seeds
Nymph Green Shieldbug, Palomena prasina
Rhopalus subrufus, one of the most abundant today
The first Green Shieldbug Palomena prasina adult of the year
Likely Corizus hyoscyami nymph. Thank you to Dave who identified it in a comment.
Dolycoris baccarum Hairy Shieldbug

This dark Forest Bug, Pentatoma rufipes, had a ride home on my trousers 

I must remember to leave my geranium seedheads for next year, as true bugs (hemiptera) are one of my favourite insects. One job less to do, and plenty of opportunities to enjoy bugs.

Saturday, 8 September 2012

Queens and kings on the wing!

We've enjoyed a whole week of warm weather and no rain. Today, garden ant queen, Lasius niger,  that had already lost its wings, was running on the pavement, and on my local wildlife garden, nervous workers on the path made me look closer. When new winged queens and male ants are ready to emerge, workers follow them run frantically about. And emerging they were, for at least the third time this year, many queens and smaller numbers of male ants. Some queens were trying, unsuccessfully to fly straight from the ground, others, like the one above, reached for a higher point, to get a better chance to take to the wing.
Winged ant queen, Lasius niger, revving its wings on the ground
The couple of queens above started climbing a fence post while the workers followed them. Although many winged ants will eventually take to the sky, where they find their mates, a Zygiella x-notata web hung with entangled winged ants on top of this fence post. That spider is going to have a super dinner tonight.
 I have never seen flying ants this late in the year, have you seen any winged ants recently? The Society of Biology is carrying out a Flying ant Survey, where you can submit your records.

Tuesday, 4 September 2012

Dispersing Pholcus babies and the spider man

A few months back, I bought a tattered copy of the classic The World of Spiders, by W.S. Bristowe, the 38th book of the New Naturalist series. This book is a wonderful read and I recommend it to any spider enthusiast. Bristowe was in awe of spiders from an early age. He describes being greatly puzzled -  when he was able to read -  and after devouring any spider book he could get hold off, that
the great experts seemed to leave off where I wanted to begin. They had described with precision the appearence of the corpses, in words often unfamiliar to me, and had left to other people the task of writing about their habits
His book does not disappoint as he went on to describe the behaviour of many familiar and unfamiliar spiders with their own observations, displaying the author's never ending curiosity for the world of spiders. The book has photos (black and white and colour) and astonishingly beautiful line drawings by Arthur Smith, often portraying his subjects going about their business and demonstrating an incredible attention to detail. Bristowe describes his first meeting with Smith in the preface of the book:
he ended the afternoon perched on a table with a torch under one armpit whilst he busied himself with pencil and paper sketching a Pholcus on the ceiling.
Bristowe seemed to have a particular fascination with Pholcus phalangioides, the daddy long legs spider.
Pholcus did not live in my childhood home at Stoke d'Abernon, Surrey, although she thrived elsewhere only about ten miles further, so the quest of an explanation inspired me to trace her distribution. This had to await the acquisition of a motor-bycicle and then, with the impudence of youth, I zigg-zagged across England ostensibly seeking rooms in hotels or lodgings whose ceilings I viewed with nonchalant interest. My apologies are no doubt due to a host of hoteliers for gaining entry under false pretences...
 On the 23rd of August I noticed that the eggs from an egg sac a Pholcus phalangiodes female in the toilet had been holding had hatched. She was still holding the empty egg sac (above), and twenty-two  spiderlings hung still, upside down around her. In Bristowe's words:
The eggs may hatch in two or three weeks' time and the young then hang motionless like washing on clothes-lines for the next week or fortnight during which time they take no notice of any disturbance such as those caused by their mother catching an insect. Unlike nearly all other spiders, they do not molt until after they have emerged from the egg-sac.
  Directly they have recovered from this first molt they gradually begin to migrate, taking positions further and further along the wall and spacing themselves as though they had staked their claims to particular territories. Now they are interested in food and for several of them their first meal is of a brother or sister who is backward in his timetable of who dies or is injured as a result of the delicate operation of moulting.
A couple of days ago the spiderlings moulted and today, at the tender age of 12 days, some more adventurous spiderlings have started to explore and disperse away from their mother, their old skins hanging like ghostly gloves from the invisible web.

More information
Bristowe, W.S. 1958. The World of Spiders. The New Naturalist. Collins, 304 pp.

Monday, 3 September 2012

Night pollinators

Although daytime pollinators get a lot of press, night time pollinators are important too. Many moths feed on flowers at night, and some species of flowers appear to have evolved to be pollinated mainly by moths. If you go out to the garden on balmy summer nights, such as the ones we are enjoying this early September, you are likely to see Silver Y, Autographa gamma, feeding. This lively moth looks like a blur as it flutters continuously while it feeds - the flash creates a false 'frozen' effect. Like another summer visitor the Hummingbird Hawkmoth, the Silver Y has a very long tongue which allows it to feed on Honeysuckle, Lavender, buddleia, peas and wallflowers (above). All photos taken yesterday and today in the garden.
on honeysuckle
on lavender
...and on wallflower Erysimum Bowles Mauve
 And they must be careful on their comings and goings, while flying above them, Pipistrelle bats are hunting...

Sunday, 2 September 2012

Male garden spiders out on a mission

Even my four year old has noticed that there are lots of spiders about. She found many fresh webs by Araneus diadematus today, and she asked why are there so many now. I tried to explain that they have grown large recently, and that's why we are seeing them more easily, but she discarded this and came up with her own explanation: is her watering the plants yesterday what must have made them grow. Female Araneus diadematus are reaching quite large sizes now, although there is a lot of size variation. The record holder in our garden sits by two rubbish bins, and has probably been gorging on the flies the rubbish attracts. Males have also reached adulthood and, in contrast to the sit-and-wait females, are moving between bushes in search of receptive females. I have come across three in the last few days. They have slimmer abdomens and robust legs and their palps are quite noticeable. The male must be careful, though, as females will quickly make a meal of him if he does not reach their high standards. I found this male getting closer to a small female's web. As he was on a broom, focusing him was very tricky and I resorted to trying the white bowl.

Forked tailed flower bee on common toadflax

I planted a new bed with native flowers earlier in the year: foxgloves, hedge woundwort, common toadflax, oregano and bird's foot trefoil. It has been very popular with bees and other insects, but there was the one plant that I hadn't seen being visited: the common toadflax, Linaria vulgaris. This relative of the snapdragon has spikes of closed flowers that require some effort for insect to access the nectar and pollen. On top of that, the flower has a very long spur which contains the nectar, so only long-tongued bees can reach the nectar - barring nectar robbers which will make a hole in the spur. The wait was worth its while, as last week, later than I have seen this species before, a female Anthophora furcata turned up and fed on all available flowers, collecting the pollen. She was also pollinating the flower, you might see the flower's anther pushing against the bee's head. The bee came back again the same day for another visit. She had large bare patches on the abdomen and thorax, but still showed the characteristic fringe of red hairs at the end of the abdomen. The flowers are beautiful, it is a native plant and it attracts one of my favourite bees, what else can one ask for?

UPDATE 20/09/12
Since writing this post, I have watched the long tongued bumblebee Bombus pascuorum visiting these flowers too.