Tuesday, 13 October 2015

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.

Monday, 12 October 2015

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.

Sunday, 11 October 2015

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.

Saturday, 10 October 2015

Lycosidae: wolf spiders

There are 37 British species belonging to this family. Lycosids or wolf spiders are medium to large species that are usually found running on the ground, although are burrow dwellers and others live near water, and can dive for safety. They are highly visual spiders, and have a pair of large eyes and then two small pairs in a row underneath and two middle sized ones on the side of the head. Most species are active during the day, with a strong tendency to bask in sunny spots in the open, often in large numbers in some species. When resting they fold their front legs underneath their body, and leave the rear legs stretched. When disturbed they can quickly run, even jump, for cover. They can be remarkably camouflaged in their habitats.

Wolf Spiders typically mature in the spring. Adult males spend much of their time finding and courting females. They might locate the female first using pheromones, but the courtship display uses mainly visual cues. Male palps or front lets tend to be dark and males will wave them up and down alternatively, vibrating the palps and abdomen in front of females, legs stretched as in tiptoes, approaching a little bit in between signals. Females may accept the male by tapping their front legs rapidly on the ground, however they often retreat, or lunge at the males to scare them off. This rarely deters the insistent male for long. Read this post in BugBlog for more on the courtship of these spiders.

Mature male Pardosa sp. on the look out for females
A male courting an egg carrying female

Egg sacs and spiderling piggy backs
Their wandering nature has resulting on wolf spiders unique way to carry their egg sacs and their young. Females wrap their eggs in lentil shaped egg sacs that they secure to their spinnerets and carry with them for a couple of weeks. The female opens the egg sac to allow the spiderlings to emerge. Once they do, they climb onto their mothers abdomen and are so carried for several days.
Pardosa, likely amentata, a common species in my garden.
This is the bluest eggs sac I've seen on a Pardosa female. Possibly freshly made?
Pardosa female with her spiderlings

A wolf spider gallery
This family, as many other spider families, contains many species that are difficult to identify in the field. If you see any obvious identification mistakes please let me know.
Arctosa perita, an amazingly camouflaged species on sandy beaches and dunes (also top shot). This one photographed at Spurn Point yesterday. This species makes a silk lined burrow where she spends much of her time (read this post from Catherine Scott's blog with fantastic photos of this species and the burrows they make).
Possibly Pardosa pullata, female with egg sac, on rocky mountainside
Female Pardosa possibly amentata with egg sac, basking in the garden.
Unidentified wolf spider with spiderlings on mossy, heathland area.
Trochosa sp. on pond margin.
A Pirata piraticus, pirate wolf spider, resting on the water surface. This spider can be found on ponds and they often run across the surface, where they hunt small invertebrates.
The striking male Pardosa lugubris/saltans
Female Pardosa lugubris/saltans with egg sac

Friday, 9 October 2015

Amaurobiidae: funnel web spiders

This family has almost 700 world species of which three are found in the UK, all from the genus Amaurobius. They are large, robust spiders who produce cribellate, 'fuzzy' silk. They are nocturnal and live most of their lives hidden in silk-lined funnels in crevices in walls, tree trunks, ivy covered walls, or under logs and stones. Funnels are easily spotted as their entrance is surrounded by a messy array of lace-like silk threads extending onto the surrounding area. The silk is bluish when freshly laid and it immediately identifies its owner before you have even seen the spider. Passing insects get tangled on the threads and the resulting vibrations alert the spider sitting in her retreat. She springs out of her retreat, localises the insect and quickly bites a leg. Once she gets a good hold, she pulls the insect into her retreat.

Carding silk
Amaurobius similis often lives inside houses, and if you know where one of her retreats is, you could witness how she combs silk with the structures on her rear legs around the entrance to the retreat. Taking time to spin a few snares around the entrance each night.

An Amaurobius similis on the entrance of her funnel on the corner of a wooden fence.
Amaurobius female carding silk.

Eggs and egg sac guarding
Males mature in the autumn, when they wander in search of mature females (the top shot shows a male Amaurobius ferox, which tends to mature at the end of winter). When they find a female's web, they drum on to the threads with their abdomen and palps to signal his approach. Mating is a very swift affair.  Females lay their eggs in a silk cell on her retreat and sits by them.

Amaurobius sp. guarding her egg sac

The female's care does not end with the guarding of the eggs in Amaurobius. When the spiderlings hatch, she opens the egg sac to facilitate their emergence. They she will sit by them and eventually produce a second batch of immature eggs, which the spiderlings will devour. This first meal substantially increases spiderling survival rates. She does not end her care them, as just before she dies, she collects the spiderlings under her body encouraging them to climb over her and feed on her body. Watch this video documenting this fascinating spider's maternal behaviour:

ARKive video - Black lace-weaver - overview

Amaurobius ferox male showing his remarkable palps, which appear to be holding white marbles.

A female Amaurobius female on her blue silk threads.