Spiders in the Araneidae family, orb-web spiders

Araneidae family, overview

The Araneidae family has 2841 species world wide. They have broad bodies, with relatively short legs often with spines. Araneidae have 8 eyes, and the typical arrangement of the eyes (looking from above) is shown in the drawing below.

Arrangement of eyes of spiders in the Araneidae family

The spiders in this family spin orb webs with a closed hub, as is shown in the drawing below. They may also build a retreat away from the web. The average U. K. orb web has over 1000 junctions, and uses about 20 m of silk, but weighs under 0.5mg. Yet it can easily support the heaviest spider. Araneus quadratus can reach weights of 2.25 g when heavily laden with eggs. That is 4500 times the weight of the entire web.

Araneus diadematus web, orb web

Araneidae mating - when a male approaches the web of a female he is hoping to mate with he plucks the threads of her web to attract her attention, and to let her know he is not her next meal.

Egg sacs. Spiders in this family tend to lay their eggs sacs amongst vegetation or under stones.

Araneus diadematus, garden spider, cross spider and the diadem spider

Araneus diadematus, also known as the garden spider, the cross spider and the diadem spider

The spider above is Araneus diadematus, also known as the garden spider, the cross spider and the diadem spider. Usually very easy to recognise because of the large white cross on the abdomen. The top of the cross cannot be seen here as she is so big with eggs. It is one of the most common orb web spiders, and is found in Europe, North America and Asia, right across to Japan.

The body length of a fully grown female is 12 - 15 mm long, and a male 8 mm.

They build a large web - a typical one is seen above, but they can vary slightly according to the anchor points. The average web is around 40 cm in diameter, and 1.5 - 2.5 m off the ground if suitable sites are available. However they will build anywhere. I have one in the roof corner of my greenhouse. The female has changed the web to suit the expansion and then removal of a tomato plant, and it is certainly not the "average" shape and size. Females hide close to the web. A web can take less that an hour to construct, and will last just a day or two at most as the sticky droplets on the spiral threads get coated with dust and pollen and become ineffective. The spider doesn't waste the silk of the old web, but eats it as it is full of protein.

The spider above was found in a rose bush growing up a wall, and had been there for some months.

In the U. K. it usually takes two years for this spider to reach sexual maturity. Mating usually takes place in August and September. Mature males search out a female to mate with. When he finds one he plucks the silk strands of her web to announce his arrival, and to let her know he wants to mate and is not her next meal. Although if he doesn't make a speedy retreat after mating he might be. She will lay her yellow egg sac containing 400 - 800 eggs in a sheltered spot, probably attached to the wall, and stay with the eggs till she dies in the autumn.

The young will emerge as it starts to warm up the following spring. At first the spiderlings will huddle together in what looks like a fuzzy ball which if touched seems to explode with spiders running in every direction. Then after their first moult they will go their separate ways. You can just see the silk issuing from her spinnerets at the end of her abdomen.

It takes just 5 seconds from the time a prey item lands on the web until it is bitten and the spider starts wrapping it up in silk. Often the spider will completely wrap up the prey in silk before killing it. Sometimes she does not kill the prey immediately. She will twirl it round and round in silk until all its legs are caught up, then she leaves it hanging until she is ready for a meal.

Araneus quadratus

Araneus quadratus

Above is Araneus quadratus, probably the heaviest British spider - one weighed 1.174 g, and another weighed 0.33 g but the eggs she had just laid weighed 0.76 g, and weights as high as 2.25 g have been recorded! The spider gets its scientific name from the 4 spots on its abdomen.

The female is 9 - 15 mm long, and the male 6 - 8 mm long. The colour of both sexes varies from pale yellow to red/brown. The abdomen in the female increases hugely in size when she is heavy with eggs. It is found in tall grass, heather and bushes. The web is around 40 cm in diameter, and less than 1.5 m off the ground when there is a suitable site. Adults are sexually mature in summer and autumn. The are common in Britain and northern Europe.

Another member of this family is Nephalia sp. from New Guinea. Their huge webs are so strong that humans use them to catch fish.

Nuctenea umbratica, the Walnut orb-weaver

Nuctenea umbratica, orb web spider, underside

Above and below is another spider in the Araneidae family, Nuctenea umbratica. It has a flattened abdomen and is rather dull coloured. During the day it is found under bark and in dark crevices, all this makes it rather hard to spot. One of its favourite hiding places is in folded up garden furniture. The female is up to 14 mm long, and the male 9 mm. The female is seen throughout the year, but the male is seen in summer only.

Nuctenea umbratica, orb web spider

It emerges as it starts to get dark and spins its web to catch night-flying insects, the most common prey item being moths. It can take moths 7 or 8 times its size. It is able to do this as it has a fast-acting poison that quickly paralyses the prey. There is a line running from the centre of the web back into the spider's retreat. The spider sits in the retreat with 2 legs on this line to detect any vibrations on the web.

Araniella cucurbitina

Araniella curcubitina female

This spider is found in low vegetation, bushes and trees. It is common throughout the U. K. and northern Europe.

Female body length is 6 - 8 mm, and males are 4 mm.

The red patch above the spinnarets (see the photograph above) is the diagnostic to identify this spider.

The size of the web is small, just a few cm wide, and it is messy and disorganised compared to others in this family.

Araniella curcubitina female

Adults mature in summer and autumn. And are most commonly seen May - September. The female, above was already wrapping up a small prey item - a fly I think - when the unfortunate butterfly blundered into her web.

Araniella cucurbitina male, cucumber spider male

The mature male, above, was found in my greenhouse in July. Surely one of the most attractive spiders around. His legs are wonderful.

Also in the Araneidae family are the bolas spiders. These spiders hang from a silk thread holding its bolas (a sticky ball of silk on a thread0 by one leg. It swings the bolas so that it sticks to a passing moth. Then it reels the line, bolas and moth in. There are bolas spiders in America, Africa and Australia. In tropical America it was found that the prey items of the local bolas spider were all male "armyworm" moths. When the bolas spider was studied further it was discovered that it produced a chemical which imitated the female armyworm's sex pheromone. The the poor male moth thought it was flying towards a female eager to mate.

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