Garden blogs

Spooky or spectacular: how to identify spiders by their webs

by

Ragged webbing will be adorning many a home this Halloween, carefully constructed by skulking spiders, hiding away in the out-of-reach corners of our houses.

Autumn is often considered spider season, as this is the time we most often see them scurrying around searching for a mate. Webs that are usually invisible are also brought to our attention by hanging dew droplets and frost on cold mornings. There has been many a dewy morning here at the Botanic Garden which revealed hundreds of beautiful webs suspended on the vegetation.

There are 650 species of spider found in the UK and many spin webs in order to catch prey, building their webs across potential insect flight paths or down low to catch crawling bugs on the ground. But did you know that you can tell what kind of spider is lurking based in its web design?

Webs can be categorised into around eight broad types, each with a different design and using different types of silk in their construction. You may not be able to identify a spider with complete certainty from its web alone. However, the shape of the web will usually give a clue as to which family the spider belongs to. This post will give a brief summary of each different web type and which spider families construct them.

  1. Orb Webs

The orb web is one of the most iconic structures people most often associate with spiders. Their design is an amazing feat of architecture, constructed through the sense of touch alone! Members of five British spider families construct orb webs: orbweb spiders (Araneidae), long-jawed orbweb spiders (Tetragnathidae), ray spiders (Theridosomatidae) and cribellate orbweb spiders (Uloboridae).

The web is made out of three main components:

  • The frame thread anchors the web to surrounding supports and attaches to the radial threads.
  • The radial threads emanate from a central hub, and act as supports for the sticky spiral.
  • The sticky spiral is what actually traps the prey and its stickiness is created by glue droplets secreted by the spider. Alternatively, cribellate orbweb spiders construct their webs out of cribellate silk which acts like Velcro by sticking to the legs and bristles of insects.

After creating its web, the spider either sits in the centre or hides in a retreat, and waits for a flying insect to hit the web, getting caught in the sticky spiral long enough for the spider to strike. These webs are very delicate and so get damaged by wind and rain, and the glue droplets lose their sticking power over time. Consequently, the spider will eat its own web every day or two in order to recycle the silk and construct a new web.

  1. Funnel Webs

This type of web is comprised of a flat sheet of silk with a tubular retreat in one corner where the spider can hide from prey and predators and store eggs. This type of web is made by just one British family, the funnelweb spiders (Agelenidae). Textrix dendiculata is frequently found in stone walls, while the Labyrinth Spider (Agelena labyrinthica) spins its web low down in grass, gorse or heather. We are all familiar with the webs produced by house spiders (Tegenaria and Eratigena species), which festoon the little-used places within our homes and sheds. These spiders tend to be the ones that alarm people the most when they come dashing across the floor or get trapped in baths, particularly at this time of the year when males wander around in search of a mate. The giant house spider (Eratigena atrica) is one of our fastest invertebrates and can have a leg span of nearly 8cm. Despite looking like a creature straight out of a horror film to many people, they are not usually dangerous and can co-inhabit our homes quite happily, feasting on other pesky insects!

  1. Tangled Webs

Tangled webs may appear to be a messy and shapeless jumble of threads, but they are in fact complex three-dimensional networks of silk, intentionally designed to entangle unsuspecting insects. Tangled webs are built by comb-footed spiders (Theriidae), comb-footed cellar spiders (Nesticidae), cellar spiders (Pholcidae) and meshweb spiders (Dictynidae). The Daddy-long-legs spider (Pholcus phalangioides) is the member of Pholcidae most often encountered in our homes as it spins delicate, untidy webs in the corners of rooms at ceiling level and also behind furniture. These spiders make good houseguests as they consume unwanted household pests and they can also eat much larger spiders!

  1. Lace Webs

There are only three species of Laceweb Spider (Amaurobidae) in the UK, all of which produce a messy mesh of non-sticky, cribellate silk radiating from a circular retreat. These webs are similar to those of funnelweb spiders but with the threads more loosely spaced so that the web looks more like lace than a silk sheet, and with a distinctly bluish sheen. The webs are often constructed around crevices in walls, fences and the corners of window frames.

  1. Radial Webs

These are minimalist webs, whereby the lines of silk radiating away from a silken tube merely function as trip wires to alert the spider to the presence of prey, but the web does nothing to retain it. The spider hides inside the silk-lined holes in walls and tree bark until an insect wanders past, activates one of the radial threads, and the spider shoots out at frightening speed and overpowers its victim. Only a single family of UK spiders makes this kind of web, Segestriidae, with only three species living in Britain. The Tubeweb Spider (Segestria florentina) is the largest of the UK species of Segestriidae, with females able to grow over 2cm long, and the base of the jaws are often a striking iridescent green!

  1. Hammock/Sheet Webs

Sheet webs are slightly concave webs strung across bushes or between plant stems, often with dozens of webs blanketing a single shrub. These webs act as deadly hammocks to catch falling bugs that get knocked down when they collide with the crisscrossing tangle threads strung above the sheet. The spider usually lurks on the underneath of the hammock and grabs prey through the sheet. These webs are made by the largest family of spiders in the UK, the money spiders (Linyphiidae), which has 280 species.

  1. Diving Bells

The Diving Bell Spider (Argyroneta aquatica) is the only truly aquatic spider species in the UK, spending most of its life underwater. This spider constructs a silk diving bell between the submerged stems of water plants, and fills it with air by trapping bubbles in hairs on its abdomen and dragging them down to release beneath the sheet. Once the oxygen in the bell becomes depleted, the inflated web can also extract dissolved oxygen from the water, acting as a kind of gill! Eventually, the web collapses and the spider must travel to the surface once again to collect more bubbles, which it usually does once a day.

  1. Nursery Webs

Another type of web that is not used to catch prey is created by Nurseryweb Spiders (Pisaura mirabilis). The female carries around a large egg-sac, and when her young are about to hatch, she will construct a silk tent in the vegetation to protect her young, sheltering them until they are old enough to survive on their own.

Spiders have somehow managed to get a bad reputation over the years, despite being among nature’s most amazing architects with a great diversity of web designs and prey-catching strategies. The properties of their silk alone should be enough to warrant a huge amount of respect and admiration. Spider silk is incredibly flexible, elastic and strong, with one type of silk having a tensile strength comparable to that of a high-grade alloy steel! Spiders are also one of our largest and most important groups of invertebrates, predating on many crop pests and controlling insect numbers within our homes.

This Halloween, instead of hoovering up or sweeping away all of the cobwebs in every nook and cranny, maybe take a closer look at the spider itself and appreciate the time and effort it has had to put in to creating this remarkable structure.

 

References 

Bee, L., Oxford,  G., Smith, H., Britain’s Spiders: A Field Guide, 2nd edition, Wild Guides, Princeton University Press

Hendry, L., Natural History Museum, Available: https://www.nhm.ac.uk/discover/spider-webs.html

Hawkes, A., Bay Nature, Available: https://baynature.org/article/spiders/