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.

Gnaphosidae: ground spiders

This is a family with 33 British species, mainly comprised of agile nocturnal hunters who spend the day in a silken retreat. They are plain brown, black or grey and have short hairs that give them a shiny appearance. Some are powerfully built, large spiders. They have long, very mobile spinnerets, but unlike the Clubionidae they are divergent and the anterior pair is longer than the rest. They use them to weave their fine silk cells. One species, Scotophaeus blackwalli (above) is commonly found in the inside of houses, and can be surprised at night, when she prowls on walls in search of prey. Several genera have adopted a diurnal existence and evolved a remarkable ant-like appearance and behaviour. These are strikingly marked with spots and covered with iridescent scales.

Mate guarding and egg guarding
They mature in May of June, although the home-living Scotophaeus can mature all year round. Males often join immature females in their silk retreats until they reach maturity. The females will also make their white, often papery egg sacs inside the retreat.

Drassodes sp. pair. Males are often found together with penultimate instar females inside silken retreats. 

Scotophaeus occupying a cell in the bee hotel, guarding her egg sac.

Panthers of the invertebrate world

That's how William Bristowe described these spiders. They are indeed powerful, sleek, and nocturnal fighters. Their ability to produce sheaths of silk with their divergent spinnerets, which can move like fingers, gives them an advantage when facing other spiders. They can use these silk sheaths, coupled with their agility, to immobilise spiders larger than themselves. 

Scotophaeus blackwalli is able to prey on Pholcus, the other formidable spider predator in the house.

Male Scotophaeus blackwalli. It's spinnerets protruding at the end of his abdomen

Male Drassodes cupreus

Zelotes sp. found under log.

Ant mimics
The genus Micaria includes several species of ant mimics. Ant mimicry is actually very common in spiders and has evolved in several groups of spiders. The resemblance is often striking and specific to particular species of ants: the species on which these spiders prey (see this fantastic album of world ant mimic spiders by Alex Wild). In other cases the mimicry seems to have evolve in order to avoid predation. Micaria pulicaria can be taken for a Lasius niger garden ant. In sunny summer days when ants run on the ground, this small spider can be seen not only looking, but also behaving in the same way as ants, with front legs held up and quivering line the antennae of an ant. Micaria does not prey on ants, so from its resemblance to ants might give her a benefit of lower predation, allowing her to exploit the diurnal niche of small predators running in the open.

Micaria pulicaria, an ant mimic, which runs zigzagging across the ground rapidly, giving a remarkable ant impersonation.

Mouse spider nest

As I checked the bee hotel, the Mouse Spider, Scotophaeus blackwalli, was looking considerably thinner than last time I checked. And lo and behold! She was guarding a fresh, pure white silky cocoon holding her eggs in a neat bundle. I will update this posts with further developments.

UPDATE 9th July. The female is still sitting right on top of the egg sac.

New guest in the bee hotel

As I removed one of the sides of the bee hotel to examine the progress of the Red Mason Bee nests I found that one of the cells had been occupied by a mature Mouse Spider female, Scotophaeus blackwalli, in her silk cell, looking like she will be ready to nest soon. Although she retreated to the bottom of the groove, she was still there the following day.
These spiders wrap their eggs in round white silk sacs under bark or in crevices in and around houses, and the female sits by the nest, guarding it. These spider nests are not easy to observe without disturbance, as they may fall apart as they are uncovered, or the female might flee. I am therefore quite pleased with this new guest, as, if she decides to stay, I should be able to watch her nest with little disturbance.

More information on the family Gnaphosidae here.

The Panther Spider

Upon removing a pot from a wall this morning, I exposed a beautiful adult female Mouse Spider,  Scotophaeus blackwalli, her abdomen full and glistening. Although initially flighty, she eventually settled on the white bowl and allowed me to take her portrait. In his classic book 'The World of Spiders', packed full of interesting observations on the behaviour and natural history of British Spiders, W.S. Bristowe described these nocturnal spiders and their relatives as the 'panthers or pumas of the invertebrate world'. However, a few lines later he pushed aside their hunting habits and instead gave this spider a much less impressive common name:

If an English name were needed for our only domestic species, which is found rarely away from man's buildings in hollow trees, it would be appropriate to call her the Mouse Spider on account of her glossy grey abdomen. But she can be a very fierce mouse. She reaches 11 mm. and has short brown legs and a rather narrow head.

He goes on to describe its ability to subsist without water for months and its prowling behaviour 'at night on walls and ceilings in search of prey, retiring behind pictures or onto crevices in walls during the hours of daylight.' He must have kept this spider in captivity and observed it carefully and he goes on to describe its encounters with prey and its short mating behaviour. He describes to have observed two cases of mating in July. And it is at this time of year that adult specimens can commonly be found.

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

Hunter hunted

I feel like apologising for posting on Pholcus spiders again, but the reason is they are everywhere in my house. I read somewhere that hoovers are their most feared predators, but today I came across a chunky-looking spider, a mouse spider, Scotophaeus blackwalli (than you to No. 9 Spider from Wild About Britain for identifying it for me) holding a Pholcus on her fangs on the kitchen ceiling. I climbed on a stepladder to get some close shots, although I couldn't get as close as I wanted. The Pholcus' spindly legs stood aside while the mouse spider finished its meal. After a few minutes, the mouse spider left the Pholcus empty carcass behind. It made a change from the Pholcus being the usual spider predator in the house.

A side view from the mouse spider

UPDATE

For a beautifully filmed video of a house spider vs a Pholcus spider see