Winter active spiders in the house

We are having an exceptionally mild winter and, although much of the time it is wet and dull, winter invertebrates respond to the prevailing conditions. While some spiders overwinter in the safely of an egg sac, or as tiny spiderlings on leaf litter and tree trunks, others winter as grown young or adults. In warm conditions, some of these species overwintering as grown spiders continue to be active through the winter months, hunting or looking for mates. This post was prompted by a silky, silvery mouse spider Scotophaeus, that I found on the kitchen ceiling in the morning (above). So, I decided to investigate which other spiders were about inside and outside of the house. All the photos taken this morning.

Pholcus phalangioides.

The Pholcus spiders in my outside toilet, which is not heated, have been much more active than it is usual in winter. Pholcus adopts a curious flat position in cold conditions, but a large individual has been changing corners and looks gravid, or indeed very well fed.

Amaurobius similis with centipede prey

 In a crack at the bottom of the toilet door lives an Amaurobius similis. A couple of weeks ago I watched as a large springtail, Orchesella villosa, tripped one of her woolly silk lines. The spider sprung out like lightning out of her retreat, but the springtail, making use of its wonderful jumping abilities, escaped unharmed. Today the spider was luckier. I noticed she was out, which is unusual, and looking closer I saw she was busy with prey: a centipede, likely Cryptops hortensis.
What other spiders are out and about?
Inside the kitchen window, a mid-size garden orb-weaver Araneus diadematus, hung from her web. They occasionally wander inside and live on small plant midges or drosophila from the fruit bowl. Females have occasionally reached full size inside the house and attracted males.

A poor shot of an Araneus diadematus inside the house.

Zygiella x-notata legs visible touching its web.

On the sheltered top corners of windowsills you might find Zygiella x-notata, the missing sector spider, in a silky retreat, often next of her egg sacs and the empty wrapping, one of her front legs touching the guide thread to the center of her web. At night she comes out and sits in the middle of her web. They are active regardless the weather, building their new webs early in the morning even in hard frost.

A late start of spring

Despite the mild winter, spring is taking a while to start. It has been very windy and cool of late. The last few days have been noticeably milder and still, almost warm when the sun came out. My first Anthophora plumipes male came out on the 12th of March, a bit late, but not unusual. Then there has been a few queen bumblebees and honeybees. The striking thing is that I haven't seen a butterfly this spring yet. A queen wasp bumped against the conservatory window a few days ago, but I couldn't identify it to species. Today, I found a very sluggish queen Common Wasp, Vespula vulgaris, inside the conservatory. Spring is slowly, but surely, on its way.

Supercool snails

In the last couple of months, I've regularly come across active Girdled Snails on my way to work. Damp, but often very cold even during frosty mornings I see these small snails on they way back to their day retreats on the pavement by a front garden, presumably after having been active, feeding? during the night (above, on the 23rd of January at 8:48 am). This nonchalant cold hardiness is in stark contrast to common or garden snails (Cornu aspersum), which have been dormant for a good while, and won't become active until March or April. Why is that? how cold resistant are snails? do they differ in their cold hardiness?
  Land snails are a very useful indicator species for ancient environments, as their shells fossilise very well and can be often identified to species level. Despite this, surprisingly little is known on their cold tolerance. Amazingly, 35 snail species live north of the arctic circle and 44 species over 2,000 m of altitude. How do they survive ice-cold temperatures? As other invertebrates unable to migrate snails have two strategies to survive sub-zero temperatures: freezing avoidance and freezing tolerance. Species that engage in freezing avoidance can actually be active in sub-zero conditions by supercooling. A supercooled snail will be at a temperature under 0 oC, but it won't be frozen, that is cool indeed! They can do this by producing large amounts of small sugar molecules that bind water and make their tissues more dehydrated, and also large antifreeze proteins, which inhibit ice formation even further, allowing them to remain active at sub-zero temperatures. Smaller snails (of shells up to 15 mm) appear to be more freeze avoidant than tolerant, and therefore, they are better at supercooling.

A favourite overwintering spot, with dozens of garden snails of various sizes under a tile lined against a wall in my garden.

We know a bit more about the cold tolerance of garden snails, thanks to the research of Armelle Ansart, from Rennes University and her colleagues. The garden snail has limited supercooling abilities, it is a partial frost tolerant species (they can only survive to a minimum of -5 oC). The are partially freeze-tolerant, avoiding freezing by emptying their guts - gut contents can start the formation of deadly ice crystals, reducing the water content of their body (which makes soluble chemicals more concentrated and decreases the temperature at which ice crystals form) and producing an epiphragm, a hard, thick calcareous layer of mucus that seals their shells shut, keeping the deadly moisture out. As an aside, the epiphragm is also produced in very dry weather, during aestivation, another dormant state in snails, but then the epiphragm keeps the moisture in.

An early waking young garden snail (28 Feb 2011), still carrying its epiphragm attached to its shell.

The preparation for overwintering seems to be kickstarted by the decreasing photoperiod of autumn, rather than temperatures dropping. Garden snails also seek high and dry microhabitats to overwinter and congregate, sometimes in very large numbers in favourable spots, such as the underside of logs, stones or holes in tree trunks. Large garden snails are more resistant to the cold than small ones, as they are better at avoiding the formation of ice crystals, so adults are more likely to survive a hard winter than immature snails.
 As for the Girdled snail, sadly I found nothing, although a comparative analysis of cold hardiness by Ansart and colleagues found out that its congeneric species Hygromia limbata freezes at -7 oC, not too impressive when compared to the tiny Columella edentula, also a British species, which doesn't freeze until the temperature descends to -17 oC, but probably enough to allow it to survive in the mild frosts of Hull.

References
Armelle Ansart, Annie Guiller, Olivier Moine, Marie-Claire Martin, Luc Madec. 2014. Is cold hardiness size-constrained? A comparative approach in land snails. Evolutionary Ecology, 28: 471-493. Here.

Ansart, Armelle, and Philippe Vernon (2003) Cold hardiness in molluscs. Acta Oecologica 24.2: 95-102.

Ansart, A. & Vernon, P. (2004). Cold hardiness abilities vary with the size of the land snail Cornu aspersum. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 139: 205-211.

Overwintering lacewings

On a visit to a local nature reserve a couple of weeks ago I looked to the ceiling of one of the hides, hoping to find overwintering butterflies. I didn't find any, but realised the hide contained several hundred lacewing, loosely clustered together in groups all around the ceiling and wall edges. It is something I had never come across. I believe these are one of a group of similar lacewing species, Chysoperla carnea group. Some of the individuals have started to change colour.

First queen wasp

The first queen wasp of the year got herself trapped in the conservatory. She was cold and calm, so I decided to give her a session with the white bowl. I held her in a tissue and placed her onto the bowl and she posed nicely. After a few photos, with me breathing onto her, she warmed up, started grooming her antennae and flew onto the window, and I let her go.
 The only overwintering stage of social wasps are queens. Males died at the end of the autumn after mating, and the workers a bit earlier. Their large paper nests are now empty, as the life cycle of social wasps lasts for less than one year. Queens overwinter in buildings or other dry places, but the strong wind and mild temperatures have probably helped stir this one out of her hiding place.
 The 'anchor mark' on her face identifies her as a common wasp, Vespula vulgaris.

Side view showing how hairy she is.

And a little grooming of antennae before flying off.

Overwintering

 BugBlog has been dormant for a few weeks. Somehow, posts somehow never went past the project status. But today, the sun shone after days of rain and gloominess, and in a walk at the park, my 4 year old and I did an informal ladybird survey. We checked many tree trunks and spotted lots of ladybirds, not as many Harlequins as other years, but still the easiest ladybird to find in the park. They were quite active as it was mild, and walked on the tree trunks in the sun. More than 40 in total, as the cluster of Harlequins above nestled in a little hole on a tree trunk was a little tricky to count. A single 2 spot ladybird completed the survey.

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.

Spring unfurling

 We rose to quasi tropical temperatures for mid February today, reaching 15.5 oC in this clear sunny day. Many overwintering bugs woke up, stretched and started buzzing about. Tens, hundreds of 7 spot ladybirds everywhere, coming out from folded, dried up leaves and positioning themselves on sunny spots. I disturbed a green caterpillar while gardening and woodlice were also active.
 The garden is still very sparse in the flower front. Today the first tete-a-tete daffodil opened and there are a few primroses. That is a problem if you rely on nectar and pollen for energy. Two droneflies (Eristalis tenax) including the female on the top shot fed on honeydew on the ivy. Notice its long, dark proboscis licking the leaf and the spots of honeydew on the leaf on the foreground. Later one of them flew to the Lauristinus, which is now in full bloom, where it joined a honeybee and another early hoverfly species (Meliscaeva auricollis).  Marmalade flies (Episyrphus balteatus) were also about.

Dronefly on Laurustinus

A dead queen wasp

Marmalade hoverfly, Episyrphus balteatus

The hoverfly Meliscaeva auricollis also in Laurustinus

Three Orange ladybirds

There is a cemetery near our house which has become a woodland in the midst of the city. The old headstones, most covered on Ivy, are quite popular with ladybirds. These Orange Ladybirds Halyzia 16-guttata had found shelter under the nooks of the carved headstones, or next to Ivy stems. They are beautifully patterned, with transparent edges around the elythra and pronotum: you can see its head, which is tucked, in a tortoise-like way, underneath its partially transparent pronotum.

This species feeds on mildews. It used to be relatively rare, a marker species of old woodland, and associated to Oak, but in the last couple of decades it has broadened its diet and now feeds on Ash and Sycamore mildews, and it has become much more widespread.

Have you seen a ladybird? Record it at the Ladybird Survey Website

An early start for the butterfly year

I just sent my record of the first butterfly of the year to the fantastic Woodland Trust site nature's calendar, a citizen science website which allow enthusiast naturalists to add their phenological data. It has fantastic live interactive maps and data is also used for scientific projects. Only once before I had my first butterfly of the year in January, but Sunday's (8th) was the earliest. A Peacock, flying strong, but coming close enough to us for ID (the photo above is from a few years back). We have had very mild weather since before Christmas, and this is stirring up overwintering bugs and bringing them out. All five butterflies, which spend the winter as adults (Brimstone, Small Tortoiseshell, Commas, Peacocks, and Red Admiral) had been reported in the Butterfly Conservation website by the 8th of January.

How do bugs cope with winter?

We've had a couple of frosts in the last few days. Despite the die-hards which allow me to post occasionally these days, most insect species are nowhere to be seen throughout winter. How and where are bugs surviving the cold weather? There are various ways in which invertebrates go through the winter.

Far, far Away
Some - I'd say the lucky ones, avoid winter altogether - they are far, far away during winter, having migrated to warmer areas around the Mediterranean. These include several butterflies, moths, hoverflies and dragonflies (Red Admiral, Painted Lady -above - Silver Y and the Migrant Hawker are examples) which often lack a frost-resistant stage in their life cycle.

Slowing Down
Others stay to brave the elements, a few of them even carrying on more or less as normal, but at a much more sluggish pace. These are the invertebrates that enjoying the occasional sunbathing during rare winter sunny spells: Bluebottles (above), Winter Gnats, the window spider (Zygiella x-notata). Some moth caterpillars, like the Ruby Moth caterpillar, are found active in the middle of winter. A few bumblebee populations are starting to behave this way as the climate warms and they can make use of winter flowering resources.

Dormancy
Many insects enter a dormant state or diapause: this is the scientific term to describe what we often call 'hibernation': organisms enter a physiological state, dormancy or diapause, in which growth and feeding pretty much stop, and metabolism is very reduced. To protect their bodies against the damaging effects of freezing, some chemicals (glycerol and anti-freeze protein are two of them) are produced in their bodies to maintain cell stability and aid survival under low, often freezing, temperatures. Overwintering can occur in any stage of the life cycle depending on the species or taxonomic group  - egg, larva or nymph, pupae or adult (imago).

The beautiful blue silk cocoon of a Enoplognatha spider, ready for winter.

For example grasshoppers, aphids and many spiders overwinter as diapausing eggs. Many dragonflies and damselflies overwinter underwater as nymphs. Many solitary bees overwinter as pre-pupae in their nest cells.

A fully developed Noctua moth caterpillar in early spring

Some butterflies and flies overwinter as pupae, whereas some butterflies (Comma, Small Tortoiseshell, Brimstone), Ladybirds, queen wasps and queen bumblebees hibernate as adults. Many solitary bees are already imagos in their cells, waiting for the right time to emerge.
 I will keep my eyes open for bug life throughout the winter and be on the lookout for any stirrings indicating that springs is coming.

The face of the alien aphid muncher

This Harlequin ladybird happily eating an aphid on the 6th of November illustrates how active many of these ladybirds still are. I found young and old larvae, pupae, mating adults and also dormant adults in a small area near in my local park. Harlequins are multivoltine, and will carry on reproducing as far as conditions are suitable. In northern Europe, two generations and possibly three if weather conditions allow can occur, as adults do not need to enter dormancy before they can reproduce, as it is the case with the 7 spot ladybird.

Ready for winter

Only a couple of weeks ago, 7 spot ladybirds were mating. Today we found this little cluster, with a harlequin trying to merge in, nestled on a wall, ready for winter. More BugBlog ladybird posts here.

Mating 7 spots on 9/10/11.

Why do ladybirds overwinter in groups?

You have probably come across ladybirds clustered under leaves or bark during winter. To spend the winter, seven spot ladybirds - otherwise solitary creatures -   they seem to actively seek each other. I took the photo above a few minutes ago in my garden. I counted 16 ladybirds - most were 7-spots, with two Harlequins - on the shady side of an agave killed by this winters' harsh frosts. Before I go on to explain this communal overwintering behaviour I have to explain why ladybirds are so colourful. Ladybirds are aposematic, a term describing an antipredator adaptation by which organisms have evolved bright, contrasting colours (think on the yellow and black stripes in cinnabar moth caterpillar or wasps) to warn predators of dangerous behaviour (stinging) or distastefulness. Ladybirds belong to this later group. Their beautiful glossy red and yellow elithra with black spots is the first line in a complex defence system, a warning signal to predators, probably birds, of their foul taste. Their bodies contain a bitter tasting alkaloid. If the predator ignores the warning signal and attacks the ladybird - or if you handle them a bit roughly - they release a yellow liquid from their leg joints, with high concentrations of the alkaloid, coccinelline, in what is called "reflex bleeding".
  Given that ladybirds can secrete up to almost a quarter of their body weight during the reflex bleeding, it is an energetically demanding defence mechanism. During the winter, when ladybirds do not feed and need to save precious resources, they do not reflex bleed, although they still taste bitter. It is because of this that they cluster together: as other distasteful prey that lack a mechanism to let know of their foul taste to a potential predator, clustering allows individuals with warning coloration in a group - even if they are unrelated - to benefit from just one of them being injured or killed by a predator, as the predator is unlikely to attack further ones in the cluster.

Reference
Holloway, G., Jong, P., Brakefield, P. & Vos, H. (1991). Chemical defence in ladybird beetles (Coccinellidae). I. Distribution of coccinelline and individual variation in defence in 7-spot ladybirds (Coccinella septempunctata) Chemoecology, 2 (1), 7-14 DOI: 10.1007/BF01240660

Waking up

I came across this snail on Friday, the first active snail of the year. It was covered on cobwebs; a fragment of its epiphragm - a sturdy yellowish membrane made up of layers of mucus that the snail produces to close their shell opening during their winter dormancy period - still attached to its shell. I am not sure if this snail emerged spontaneously, as I am doing a lot of pruning in the garden these days, but even if I disturbed, it moved all the way down the wall before settling again.

Angle Shades caterpillar

After several weeks of frost and snow, and the coldest December for 120 years, we venture in the devastated garden to get some fresh air. Despite the frost, while brushing the leaves from the path, we came across a lively and fat Angle Shades caterpillar (Phlogophora meticulosa). Larvae of this common species of moth can be found all year round, while adults fly from May to October. Although, considered a pest in gardens due to the wide range of caterpillar feeding plants, the adults are large, handsome moths with unusual curled wings which make them look like a shriveled leaf, with neat brown and pink patterns. The larvae, which can be green or brown, are active during the winter, and hide under the leaf litter feeding on whatever green plants happen to be around. Come the end of March, they are ready to pupate and the fresh generation of moths will appear from mid April. In the summer, these local moths will be joined by migrant ones from the continent, as this species is also a common UK migrant.
Below there are a series of images illustrating the life cycle of this moth.

17/03/07. A large, drowsy caterpillar...

 Falls on its back, and within 24 h...

it has pupated.

The pupa took half an hour to reach the deep brown colour from the photo above.

16/04/07. A freshly emerged Angle Shades dries up on Cytisus bloom.

16/05/08. An adult found in the house quenches its thirst on Iberis.

For more information on moths see UK moths.

Shiny red ladybirds and apples

We have been picking some apples today. Our tree is of the variety Red Devil and crops beautifully large sharp, tangy and red-fleshed apples. After picking one of them, we uncovered four 7-spot ladybirds nestled together, thinking themselves all ready for winter. They will have to look for a better spot as the apples won't be in the tree much longer. Ladybirds often overwinter in groups, but this is the largest group of 7 spots I've seen.

Sleeping Snails

A sunny day like a jewel in a dull, cold winter. For the first time in months I venture out to do some gardening. There are little signs of bug activity. A few 7-spot ladybirds sunbathing; a cloud of winter gnats; a bluebottle which rapidly gets into the house through the back door...I moved an old tile left leaning against a south-facing wall and found a gathering of overwintering snails stuck to the tile and the wall. A few small ones, but mostly of them grown up snails, shell against shell. In this spot they keep relatively warm and dry during the winter. The snail secretes a specially tough mucus to seal its shell opening which can glue it to walls, or other snails.

A dormant snail operculum.

More on Garden Snails at BugBlog:

Darts for love on the strange mating tactics of your garden Snails.

Bumblebees!

The first bumblebee of the year stumbled across my path today. It was close to a large clump of flowering Mahonia, but on the footpath, so I moved it to the flowers. It was a white-tailed queen bumblebee, Bombus lucorum. Recent bumblebee records from the BWARS (Bees Wasps and Ants Recording Society) site indicated that, instead of overwintering queens, there are now overwintering colonies -mainly of the Buff-tailed, Bombus terrestris but also Bombus pratorum, so that workers can be seen foraging in the winter. As far as I know this has not happened in Northern England yet, so the first bumblebees of the year are sleepy-looking queens in search of nectar and a nesting site. It was sunny and quite warm in the morning, so this bumblebee was awaken and came across this patch of flowers. I guess in the countryside must be quite tricky to find nectar this time of year, with gorse, snowdrops, lesser celandines and few other plants in bloom. Cities and their parks and gardens have much more in offer, rosemary, Mahonia, heathers, Hebe and many other mid-winter flowering plants, and I wonder if this - combined with milder winters - has something to do with this change in reproductive strategies. It would be interesting to test this comparing the  strategies of countryside versus urban bumblebees.

Ivy fest!

The end of September is the time of the year when I like to visit an old ivy growing on a south-facing brick wall. Today was the first day I saw it flowering for good. Ivy (Hedera helix) is an unusual plant in that its flowering season starts with the beginning of autumn. Given the scarcity of alternative sources or nectar at a this crucial time of the year - when many insects are getting ready for winter dormancy, egg laying or migration, this marks a food bonanza for many insects, the final feast of the year. Drone flies (Eristalis) and green and bluebottles, hover-flies, wasps, honey bees, queen bumblebees, butterflies (Red Admirals, Small Tortoishells, Painted Ladies, Large and Small Whites, Commas) buzz on the green-yellow ivy flowers.

Myathropa florea

Helophilus pendulus

Syrphus sp.

Bluebottle, Calliphora vomitoria

Eristalis tenax

Above, an illustration of the diversity of hoverflies who use Ivy

Red Admiral

Comma

And all them must keep watch for garden spiders, who never say no to a juicy hover-fly...

By the beginning of December the Ivy flowers are gone and the berries start to grow.

 This is one of the last ivy blooms of the year, with a late red admiral (photo taken 30/10/2006):