Araneae (spiders), continued

Enoplognata ovata and egg sac

Spiders and gardens

  • The Lycosidae will eat 5 - 15 small insects each day, and in California Pardosa ramulosa is an important predator of leafhoppers.
  • The Salticidae also have a fondness for leafhoppers and will eat 4 - 8 per day.
  • In China farmers build little straw huts beside their paddy fields for the spiders to overwinter in.
  • In the UK money spiders protect the fields of winter wheat from aphids, and are active earlier in the year than ladybirds - another great aphid predator.

Amazing spider snippets

  • It has been estimated that in one year the weight of insects caught and eaten by spiders in the U. K. is equal to the weight of the entire human population. This also exceeds the weight of insects eaten by birds.
  • A hectare of meadow can contain over one million Linyphiidae (money spiders). This can be most easily seen when the webs are covered with the morning dew.
  • Spiders do not stick to their own webs because they either step on the non-sticky parts only, or secrete a special oil on their feet.
  • It is believed that spiders have been in existence for over 300 million years.
  • The largest spider that ever lived was Megarachne which lived during the Carboniferous and is now extinct. It was 33 cm long with a leg span of around 50 cm!
  • The heaviest extant spider in the world is the Goliath bird-eating spider, Theraphosa blondi, which can weigh up to 155g.
  • The smallest spider is Patu digua from Columbia at 0.37 mm body length.
  • The biggest spider is Heteropoda maxima with a leg span of 300 mm.
  • In France Tegenaria sp. are released into wine cellars as the presence of their webs is though to create feeling of age.
  • In Belgium many brewers believe that spiders are instrumental in controlling the numbers of fruit flies (Drosophilidae).
  • In 1936 a policeman on point duty on Lambeth Bridge in London held up traffic to allow a particularly large Tegenaria parietina to cross the road.
  • The longest orb web is made by Darwin's bark spider, (Caerostris darwini) in Madagascar. Its web can span as much as 25 m. It spins its web over streams, rivers and other water bodies. The orb web itself has an area of around 3 m2, but the anchor lines, which stretch from bank to bank can be 25 m long. The silk is the toughest biological material yet found. It is 10 times stronger than kevlar, and twice as strong as any other spider silk.
  • In 1760 when malaria, also known as ague, was common in Britain a Dr. Watson recommended a Tegenaria sp. "gently bruised and wrapped up in a raisin or spread upon bread and butter" as a cure !

Spider courtship, mating and behaviour

Courtship of the female by the male can be elaborate, but much of this is to make sure that the female can distinguish him from a juicy meal!

Before mating the male spider deposits a drop of sperm on the surface of a small sheet of silk, and then transfers this to his palps which pick it up by capillary action. The male's palps fit into the female's epigyne like a key fits into a lock. This prohibits mating with the wrong species.

In species which spin webs the male will pluck and vibrate the strands of the web to attract the female's attention. All spiders are very sensitive to vibrations. He may hang around the web for days before making his move.

Some species wait until the female is occupied with prey; others until she is about to moult. Some supply a prey item as a gift. In species with good eyesight such as the Lycosidae and Salticidae, the males signals his intentions with his legs and palps.

The mature male on the right was found wandering across my floor in search of a female. For this species this is common behaviour at the end of summer and during the autumn.

Copulation can last just a few seconds or many hours depending on the species. A few females will catch and eat the male after mating, but in most cases the male is not eaten, and will go off to try to find another female to mate with.

In some species the mated pair will stay together for a while, but mature males do not live nearly as long as mature females. It is then, once the male has died of old age, that the female will eat the male.

The female stores the sperm until she needs it, and this can be for as long as 18 months if conditions are unfavourable. However she will have to use the sperm before she moults.

Spider ballooning

Ballooning is done by small spiders and spiderlings. In the early summer it is done mainly by young spiders dispersing to a new area, and later in the year it is mainly adult money spiders that balloon.

To balloon the spider climbs as high up whatever structure it is on, turns to face the wind, and releases a few strands of silk. Then it lifts its body up holding on to the surface with just two front legs, and waits till the air currents carries it up.

Ballooning takes place when there is a very light breeze. Of course the spider will have no control over direction or landing place, and so many spiders perish as a result of ballooning.

Spiders can balloon to over 3000 m in height and still survive. They can travel great distances, and are often early colonizers after fire, disaster, etc.

Tegenaria duellica mature male showing palps, chelicera, fang and eyes

How spiders eat food

Spiders cannot eat solid food. They inject or pour (depending on family) digestive juices into or onto their prey. These juices liquefy the prey with is sucked up leaving only the hard parts.

Old proverb

If you wish to live and thrive,
Let a spider run alive.

Featured species