Crabby

European Green Crab Spider (Diaea dorsata)

One thing we quickly learned when trying to identify things in the garden – some spiders are hard! Many can only be identified by dissecting their genitalia, or other equally lethal methods. We're not at the point where we want to do anything of the sort, so many of the species we find go unidentified. Fortunately, there are some spiders that don't require such extreme measures, and one of them made an unexpected appearance this week. I say unexpected because although the European Green Crab Spider (Diaea dorsata) is widespread across the southern half of England, it's still pretty uncommon across this corner of Norfolk. When I entered the record into iRecord (the national database), I got a message saying it was "outside the known range of this species". 

The European Green Crab Spider is so named because its long legs and scuttling movements bear a strong resemblance to a real crab. It's quite small though; the female's body is only about 6 mm (1/4-inch) long, and the male's is even smaller, though the long legs of both sexes help to make them seem larger. In a cool adaptation, it can change its colour to blend in with its surroundings, a process that takes several days. Based on its size, the individual we saw appeared to be a female. With any luck we'll find a male. Or preferably two! Males compete by facing off with their front legs outstretched and dancing around each other – reportedly sometimes for hours. It would be fun to see such a combat. Our handy reference guide, "Britain's Spiders", says the species is strongly affiliated with woodland and prefers evergreen foliage, so I'm not quite sure how (or why) it ended up on our Norway Maple trunk, but we're glad it did!

Boxer

Philodromas dispar

Last month, I finally caught up with a spider that Mike first spotted in the garden a couple of years ago. The male Philodromas dispar is pretty distinctive: dark brownish-black with a white line running the length of its body on both sides, and yellowish legs. And how could you miss his big pedipalps, which look like a pair of boxing gloves held out in front of his face? These contain organs which allow the spider to "taste" and "smell", and the male also uses them for his courtship displays and to transfer sperm packets to the female. It's much harder to distinguish the female from several similar species. In fact, the books say you need a microscopic look at their sex organs to identify them, so I'm glad I found a male! He was scurrying along the edge of one of the flower beds, investigating the upper and undersides of leaves, weaving his way around stems and along vines, moving fast as he searched for prey. The species belongs to the family of "running crab spiders" – a group distinguished by their flattened shape and their particularly long second pair of legs. These spiders don't make webs, instead ambushing their prey. With a body that measures about 5 mm long (roughly 1/4-inch), it is said to be an "agile hunter" that tackles mostly flies and other smaller insects. It is found in various woody habitats, often near (and sometimes in) houses. It particularly likes the lower branches of trees and shrubs. The female uses silk to attach her eggs to a leaf, and guards them until the autumn, when the spiderlings hatch. They overwinter either in leaf litter (according to the UK Spider and Harvestman Recording Scheme's website) or under bark (according to the Nature Spot website), emerging again in the spring. The species is common in southern England and Wales, as well as southern and western Europe. No doubt, we'll be seeing them again.

Spinner

Microlinyphia pusilla

One of the things this project has been great for is helping me to conquer (sort of, anyway) my very irrational fear of spiders. Knowing that there are no dangerous (native) spiders on these islands certainly helps with my comfort level. But it's the process of putting a name on our eight-legged fellow residents that's doing the most good. Heck, I've even gotten to the point where I can pick them up and put them outside if I find them in the house – well, most of them, anyway. This little lady was investigating the back of one of our outside chairs on this date a few years ago, and I finally got around to identifying her today. It's a female Microlinyphia pusilla, a common and widespread species across most of Britain (as well as much of central and western Europe). This species is particularly partial to grasslands, but is found in a variety of other habitats as well. Its web is a horizontal sheet spun in low vegetation. Females are larger and plumper than males, with a dark central line on their mostly white abdomen, often with triangular dark patches overlapping towards the back end. The whole abdomen is surrounded by a dark band too. Males are shiny and black with a narrow abdomen that often shows two white spots near the front edge. Adults are seen from spring into mid-summer, with a few persisting into the autumn, so we should be seeing them around for a few more weeks yet.

Missing sectors

Missing-sector Orbweb Spider (Zygiella x-notata)

While rummaging around the part of the garden near the house recently, looking for likely suspects to photograph, I came across this spider strolling unsteadily along the windowsill. It was a rather chilly, windy morning, so she might have been a bit cold. For whatever reason, she was in the open rather than hiding away, so I was able to get her picture. This is a Missing-sector Orbweb Spider, named for its habit of leaving an empty section in its otherwise normal orb web. (Think Charlotte's web with the radial lines missing in one of the upper sections.) A single thread crosses this empty section from the center of the web to its edge, where the spider sits in a retreat it has built there. The thread acts as a signal line, with its movement alerting the spider, which is holding the thread between its front legs, to the presence of any prey caught by the web. This line allows the spider to zip quickly to the middle of the web without having to negotiate sticky threads. Interestingly, if the plane of the web varies from the angle of the signal line by more than 40 degrees, the spider doesn't leave a sector missing. Presumably, that's because it can parachute in on the line without having to worry about getting caught in its own web.

In most examples of this species, the pattern on the abdomen is silvery-grey with darker edges; in fact the spider's other common name is Silver-sided Sector Spider. (This particular individual appears to lack that colouring.) The silver comes from very thin crystals of guanine beneath the spider's skin — the same substance as that found in fish scales. While the silver of a fish's scales help to camouflage it from below, scientists aren't sure how such colouring helps spiders.

As with most of the spiders we've been able to identify so far, this one is very common and widespread across Britain. It's found across pretty much all of Europe and the Middle East, as well as along both coasts of North America, throughout the Japanese islands and in other scattered locations in Asia and South America. This species is nearly always found in association with us humans, and we have undoubtedly carried it around the world with us. It's particularly common in the upper corners of window frames and doorways, occasionally venturing as far as roof eaves and fences, or even into garden bushes. It's also regular around boats and docks. Away from humans, it's sometimes found near cave entrances. As the British Arachnological Society posits, perhaps it moved from caves to houses with us!

Walnut Orbweb

Walnut Orbweb Spider (Nuctenea umbratica)

An early breakfast out on the "raptor mound" recently revealed a new species for the garden: the abundantly widespread Walnut Orbweb Spider (Nuctenea umbratica). It was headed back to its daytime hiding place behind a slab of bark, which is slowly separating from the decaying stump of a long-dead Leylandi at the edge of the property. That's one of its favoured hiding spots, apparently; away from buildings, this species is often associated with dead wood. During the day, it hides away. At night, it crawls out and spins a large orb web — the familiar, tidy, circular web we all know and recognise as the classic spiderweb. Then it sits at the centre of that web, waiting for unwary nocturnal insects to blunder into the sticky strands. As with all spiders, the female is larger than the male. Other than that, the sexes are similar in appearance. Their dark colouration, "leathery" look, and distinctively flattened shape help to identify them, as do four pairs of small "dimples" that run down either side of their centre line. Females are found virtually every month of the year, though far less commonly in December and January. Males are more typically summer creatures, with most appearing from May to September. We have lots of time to enjoy these handsome creatures then — here's hoping they don't get too close to our moth trap!

World Wide Web

With autumn's arrival, we've seen a flush of Garden Cross Spiders (Araneus diadematus) all over the property. The source of their name is pretty obvious when you see them from behind; they have a very distinctive cross of pale spots across their fat abdomens (see left). They're relatively easy to identify from underneath as well, thanks to their very stripey legs and the two pale spots on the dark patch under their abdomen (see below). They come in a variety of colours from pale yellow to burnt orange to very dark brown, and their intricate webs are conspicuous, particularly after a bit of rain. At the moment, we have about eight webs tying our rubbish bin and recycling bin together, and another curtain lacing together the honeysuckle climbing up the wall outside our office. The spider typically hangs head down in the middle of its web and waits for flying insects to blunder into the web's sticky strands. This is a common spider throughout much of the British Isles (except for northern Scotland) and western Europe, and has been introduced throughout North America too.

Labyrinth

While working in the garden yesterday, I found this rather fearsome beastie chopping up a caterpillar that had strayed onto its web. It's a Labyrinth Spider (Agelena labyrinthica), which builds a big sheet web with a large funnel low in the vegetation. According to Britain's Spiders, they often build their webs in gorse, heather or brambles, but this one had chosen an as-yet-unidentified plant along the edge of the flower border. (It's only in leaf at the moment, and we can't remember what we planted there!) The Labyrinth Spider is a widespread species in southern England and Wales, but only rarely found north and west, and missing completely from Scotland and Ireland. It's not QUITE as big as it looks here; its body was probably only about 1/2 an inch (8-9 mm)  long, though its long legs made it seem much bigger. Its dark abdomen with the pale medial stripe and pale chevrons is distinctive, as is its carapace (the front end) with the alternating bands of light and dark (light on the lateral edges and the center, with darker stripes between). The large pedipalps (those "boxing gloves" extending from the front of its body) suggest that it's a male. These appendages, which are used in sperm transfer, are considerably larger and more swollen in shape in males than in females.

Stretch

Tetragnatha montana (underside)

While I was photographing pollinators around our Skimmia bush the other day, I spotted the spider in the picture above; though it was small and very slim, its bright silvery-white striping was eye-catching. I took the picture and went in to identify it — only to discover that this was the underside, and that there are several species that show similar patterns. Getting the "top side" photo took a few additional days (since I didn't want to disturb her), but this afternoon, I finally found her stretched out on a leaf, catching some sun (see below). It turns out that the plain dark "sternum" of the spider's underside is important; some species show a little yellow triangle at the head end. Tetragnatha montana, however, does not. The combination of the lack of the yellow triangle on the "sternum", a yellowish-brown carapace (the top side of the spider's front section) with a dark midline (and a few radiating dark branches) and that dark underside to the abdomen with its two silvery-white stripes is distinctive. This is a common and widespread species in southern England.

The six British species of Tetragnatha spiders, informally known as "stretch spiders", are notable for their very long legs and very long abdomens. They'll leave their webs if disturbed, and extend their legs straight out in front of them along a blade of grass or reed stem or twig (i.e. "stretching"), which helps to camouflage them. They've got 8 eyes in two rows of four; click on the photo below to enlarge it if you want to see them clearly. The spider's location (away from water) and its size (its body just under half an inch long) also suggest this species. To be 100% sure, I'd have to examine its genitalia under a microscope — and I can't even pretend to be interested in doing that at this point!

Tetragnatha montana 

Nurseryweb Spider

Nurseryweb Spider (Pisaura mirabilis)

When it comes to spiders, I'm a bit of a weenie; I've been a serious spiderphobe for as long as I can remember. I'm trying hard to conquer my fears, though, and one of the things we did recently to help was purchase a copy of Britain's Spiders. Our thought was that if I learned a bit more about them, maybe I'd come to appreciate them, and wouldn't have to whistle the Spiderman theme song (Mike's cue to come and rescue an 8-legged intruder) quite so often. Today, while I was mooching around the garden, I spotted this one doing a bit of sunbathing on a leaf low along one of our hedges. A quick look in the book turned up its ID. It's a Nurseryweb Spider (Pisaura mirabilis), the only member of its genus in Britain. (There are others elsewhere in the Palearctic.) The sexes are similar in appearance and size, so I'm not sure if this is a male or a female. Apparently, this species is extremely variable in colour and pattern, but always shows that wavy-edged stripe down the middle of its back. The book specifically mentions it sunbathing with its first and second sets of legs outstretched and held together — how's that for an ID feature?!

The spider gets its name from its parenting style. The female carries her egg-sac full of unhatched spiderlings around under her body. Once they've hatched, she deposits them in a tent-like web she's made in low vegetation, and guards the outside for several days, until they're ready to be on their own. Nurseryweb Spiders are common and widespread across much of England and Wales in a variety of habitats. Interestingly, they're the only spider species in Britain where the male presents the female with a wrapped "present" (aka a meal) before mating — presumably as a distraction to avoid being eaten himself!

Zebras

Common Zebra Spider (Salticus scenicus)

Heading out to the recycling bucket yesterday, I spotted this little hitchhiker catching a ride as I swung the door open. It's a jumping spider called Salticus scenicus, or Common Zebra Spider, and it's found across the whole of the Northern Hemisphere. This one is a female; she has paler legs than a male would have (yellow-brown with darker rings at the joints rather than all dark) and smaller chelicerae (the jaws and fangs just visible in between her front legs). Though she may look rather large and scary in the picture, in real life she's pretty tiny, measuring a mere quarter-inch long.

These spiders tend to hunt from vertical surfaces (like doors). Rather than spinning a web, they leap on their prey, sometimes from a fair distance away. While they generally hunt spiders and insects even smaller than themselves, they have reportedly been recorded taking prey up to three times their own body length!