Theridiidae: Cobweb weavers

A large spider family, including some very famous world spiders such as the North American black widows (Latrodectus sp.), the Happyface spider (Theridion grallator) and the social spider (Anelosimus sp.). The 56 British species are small to medium spiders. They make irregular webs of criss-crossed threads with some of them stretched and loaded on one end with sticky dropplets, which break when an insect struggles to break free and lift the prey in the air like snares. The genus Episinus, however, produce the most remarkably simplified web, a 'H' shaped with four sticky threads connecting the spider to the ground and an over head support. Theridids have a relatively large, well marked abdomen with a diversity of patterns and colours.  This family includes one of the most fascinating examples of maternal care in spiders.

Powerful hunters
These spiders are able to throw sticky threads over prey to immobilise them. This ability, and their rapidly acting venom, makes them formidable hunters able to subdue much larger prey.

Steatoda bipunctata with immobilised Ectemnius wasp

Even the powerful and agressive male Anthidium manicatum couldn't escape Enoplognatha sp.

A wasp? No problem for Enoplognatha

Not even a honeybee. Note the typical web of Enoplognatha, tangled around a flower, ready to catch visiting insects, with the spider neatly hidden under the flower itself.

Enoplognatha doesn't even care about the chemical secretions of shieldbugs.

Colour polymorphism
Enoplognata  comes in several colour morphs. There is a white morph and one with a pink stripe. This is the pretty and rarer pink morph.

Stridulating males
Steatoda bipunctata males have a serration at the end of the cephalothorax which rubs against teeth at the front of the abdomen making an just audible stridulation which is used during courtship. In his field guide to the Spiders of Britain and Norther Europe, Michael Roberts writes:

I first heard this in use as a medical student. Quietly studying the anatomy of the brachial plexus, I became aware of a quiet sound from a guitar standing in the corner. My initial thought was that one of the well worn strings was very slightly creaking as if about to snap and I  clearly remember tensing myself for this not uncommon event. It turned out to be a pair of Steatoda bipunctata mating inside!

This is the male of Steatoda bipunctata. It waves it's large palps as it runs on the ground looking very ant-like. The female (top shot) has a look reminiscent of a fat tick, its cephalothorax almost hidden by her large, shiny abdomen.

Maternal care
Theridids make egg sacs that are attached to their web, or under a curled leaf retreat, and are often guarded by the females. Some species even carry the egg sacs attached to the spinners. The presence of females protects the eggs from predation, for example from ants. The mother will react to the presence of ants by relocating the egg sac more centrally on the web. Enopognatha guards her egg sac under a curled leaf and stays with the spiderlings until her death.
The small Theridion sisymphium female produces a bluish egg sac, which she guards. When the spiderlings emerge she will feed them  mouth to mouth with regurgitated food. Later, she will share prey with them until they are ready to disperse.

The wonderfully weird egg sac of Theridion pallens

The blue egg sac of Enoplognata sp.

The tiny Theridium pictum with her egg sac (note the screw head for scale). This species lives near other spiders webs and steals food from them. 

Enoplognatha with her brood inside a curled leaf.

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.

Agelenidae: funnel weaver spiders

The agelenidae comprises 11 species in three genera, the best known, Tegenaria, or house spiders, includes several species difficult to identify without microscopic examination, and some that hybridise, further complicating identification. They weave sheet webs ending in a funnel. The spiders of this family, in particular house spiders appear to elicit fear or disgust in many people. Even William Bristowe, passionate arachnologist, confessed his 'horror' of the house spiders. The male's habit of rapidly running across the floor in the night, or appearing in the bath in the morning doesn't gain them any friends. Their amazingly long, hairy legs and large size doesn't make them endearing either. 

Males on the prowl

Tegenaria males mature in summer and autumn at two years of age and it is at this time of the year that them, which would have been living unobtrusively, in the corner of a room or behind a counter in the kitchen, leave their webs in search of females. They are most likely to be encountered then, either running across the floor a night or, in the morning, having fell into a bath from which they cannot escape. When a male meets an immature female he will stay on her web, waiting for her to mature and eventually mating with her. She accepts the male in her web and after more mating, the male will die.

A male Tegenaria sp. in the bath.

A Tegenaria moving across the floor.

Maternal spider

Female Tegenaria will lay several batches of eggs in spring in eggs sacs decorated with soil, debris or remains of prey. The spiderlings remain on their mothers web for a few weeks until ready to disperse. Read more about this topic in this post at Bugblog.

A female Tegenaria by her sheet web.

Tegenaria on her sheet web on ivy. I enticed her out of her retreat with some water spray.

A male Tegenaria, probably a T. gigantea x saeva hybrid. Males are slimmer and have longer legs than females. The modified male palps, used during mating, are visible in this photo and in the top photo of the same male.

Clubionidae: Sac spiders

The Clubionidae has 24 British species, mainly in the genus Clubiona. They are small to medium spiders usually of plain brownish colours, often with dark chelicers, and silky appearance. They have eight round eyes of similar size. Spinners are long, but converging, protruding from the end of the abdomen. They hunt mainly at night, without the help of a web, and spend the day in tightly woven silk cells they weave under stones, between leaves or in loose bark in trees and bushes. Species are difficult to identify in the field.



Egg sacs
The spiders mature in spring and summer and courtship is not very elaborate. Mating sometimes happens on the female's retreat. Females will also lay eggs within the retreat, where they guards their clutch and later, the spiderlings. Some species fold up or curl a leaf and lay their eggs in the fold, which the female then closes with white silk, with her staying inside.

Clubiona corticalis

Male Clubiona sp.

Female Clubiona in cell with spiderlings.

Male Clubiona sp. inside his cell between a window pane and leaf.

Clubiona with the chewed remains of her spider prey Amaurobius.

Tetragnathidae: stretch spiders or long-jawed orb weavers

This is a large world family, with only 14 British species. Most build orb webs and sit in the middle, instead of having a signal thread and a retreat as in typical orb weavers (Araneae). Tetragnatha are very elongated spiders with slender bodies and long legs, except the third pair, which is short and often hold the spider to stems and grasses while the remaining pairs are stretched forward and back. When disturbed, they run out of their web and stretch themselves along leaves or stems. Some species have a preference for damp places and one of them Meta menardi, lives in caves and other dark places. One of the genera, Pachygnatha, does not build webs when adults.

The locking of the jaws

Males and females have extremely long chelicers furnished with internal spines. Males have two pair of additional large and spines protruding from the inside and outside of his chelicers. These spines lock the female's chelicers open during mating. The male's palps are also very long. For a video of a mating pair of Tetragnatha click here and for a fantastic post by Catherine Scott with observations of mating and male competition click here.

Tetragnatha extensa on resting posture on a leaf over the pond water.

Tetragnatha extensa turning on a leaf allowing to see her chelicers.

Tetragnatha extensa on her web over a pond

Female Metellina sp. on her web. Metellina females are quite plump and don't have particularly long legs.

Male Metellina guarding a female's web. Unlike the female, he is slender and looks more similar to Tetragnatha. He will wait until a female catches an insect to mate. For more information on this species mating strategy see this post at Bugblog.