Spiders are small, eight-legged creatures that are best known for spinning silk webs. They spin webs so they can catch insects for their food and even larger and stronger insects cannot escape. All spiders spin silk but some don’t spin webs. Bolas spiders spin a single line with a sticky end. Any insect near, gets trapped when the spider swings the sticky line near them. They all have fangs and most kinds have poison glands. They use their fangs and poison glands to capture their food. A spider’s bite can kill insects and other small animals. A few species are harmful to human beings. In North America, six species harm people, they are – the Brown Recluse, Sac, Black Widow, Brown Widow, Red-legged Widow and the Varied Widow. Four of the Widow females are known to bite humans. The bites of these six spiders often cause mild reactions. Usually a person irritates a spider several times for it to bite you. In Australia, the most dangerous species is the Funnel-Web with the Red-back, a type of Black Widow, also being dangerous. Spiders are helpful to people because they eat harmful insects. They eat grasshoppers and locusts which destroy crops. They also eat flies and mosquitoes which carry diseases. They feed mostly on insects but some capture and eat tadpoles, small frogs, small fish and mice. Most females are larger and stronger than the males and occasionally they eat males. They can live anywhere they can find food like fields, woods, swamps, caves and deserts. One kind of spider spends most of its life underwater. Another kind lives near the top of Mount Everest, the world’s highest mountain. Some live in houses, barns, and other buildings. Others live on the outside of buildings, on walls, windscreens and corners of doors and windows. The life span of arachnids in temperate areas is a single season, therefore they rely on eggs to perpetuate the species from year to year. In warm regions, certain groups (some scorpions and tarantulas) appear to live more than a single year, in fact some tarantulas in captivity have survived for as long as 20 years. There are more than 30,000 kinds of spiders. Scientists believe there may be up to 50,000 to 100,000 kinds. Some are smaller than than the head of a pin but some are larger than a person’s hand. A South American tarantula is measured at 25 centimetres but that is with its legs extended. Most people think spiders are insects but scientists classify them as arachnids. Insects are different in a number of ways. Spiders have eight legs but ants, bees, beetles and other insects have only six legs. Most insects have wings or antennae which are feelers. Arachnids include daddy long legs, scorpions, mites and ticks. Scientists classify spiders as either true spiders or Tarantulas, according to certain differences in their bodies such as the way their fangs point and move. In addition, spiders can be grouped according to the way they live. Web spinning spiders spin webs to catch insects. Others lie and wait for insects to come.
The jumping spider family contains over 500 described genera and over 5,000 described species, making it the largest family of spiders with about 13% of all species. The Zebra Jumping Spider (Salticus scenicus) is one of the most familiar of the British jumping spiders, and is often found on sunny house walls. They reach a size of just 5mm and can be recognized by their jerky stop – start movements. As the name suggests, this small and attractive spider is black with stripes of shining white hairs. Males can be distinguished from females as they have a set of huge jaws that are used in battles with other males. Jumping spiders do not make webs; instead they actively hunt their prey by creeping up and then jumping on them (they can jump 50 times their length) and disabling them with their jaws. They are equipped with excellent eyesight, and probably have the most developed eyes of an arthropod. Four of the eight eyes are large and forward facing giving it stereoscopic vision; the other eyes are arranged so that the spider can see completely around its own body. If you slowly wave a finger at a Zebra Jumping Spider it is likely to turn so that it has a good view of you. They leave a line of silk behind them in case they should lose their footing. The male Zebra Jumping Spider has a pair of leg-like appendages called pedipalps (or simply ‘palps’) that are used to transfer sperm to females during copulation. During courtship, a male Zebra Jumping Spider has to be very careful when approaching the female, or she may react aggressively or even mistake him for a prey species. He signals to the female with his front legs before mating. Zebra jumping spiders are more likely to flee from humans than attack them, but they can bite – although the venom is not considered medically threatening. This species is widespread and common throughout Ireland.
The House Spider is probably the best known and perhaps the most hated of the Irish spiders – it is fairly large and hairy with long legs. It varies in colour from pale to dark brown, with variable sooty markings on the abdomen. Male and female house spiders are similar in appearance, but males have a more slender abdomen and longer legs. Although often detested, the House Spider provides a service wherever it occurs, reducing the number of flies and other unwelcome insects from our homes, so they are “nature’s safest insecticides”. It makes a flat sheet-like silk web, typically with a tubular retreat at one corner. These webs can become fairly large when undisturbed. When an insect falls onto the web, the spider dashes out from its retreat, seizes the prey and returns to the retreat to consume the meal. Male House Spiders are usually seen more often than females, as they wander widely in search of a mate. After a male has found a female’s web he will stay with her for a number of weeks, mating with her repeatedly during this time. He then dies and the female eats him, the nutrients within the male contribute to the development of his young. The word ‘spider’ derives from the Old English word ‘spithra’, which means ‘spinner’. Spider webs have been used to heal wounds and staunch blood flow for many years. Found all over the world, the House Spider is common and widespread throughout Ireland and Europe.
The cellar spider is commonly referred to as “daddy-long-legs” because of their very long, thin legs, and as their name implies, are found in dark and damp places like cellars and basements. The cellar spider seems to fare better in areas with higher relative humidity. Unlike other spider species, cellar spiders prefer to live within close proximity to one another, creating troublesome communities within human dwellings. These spiders build loose, irregular, tangled webs in corners, and hang upside down on the underside of them. The webs are not cleaned but rather new webs are continually added. This habit can result in extensive webbing in a relatively short time. When disturbed on its web, the cellar spider has the habit of rapidly shaking its body in a rotary movement to confuse and entangle the prey. Like most other spiders, cellar spiders are highly adaptive and successful predators. Their diet consists primarily of insects, which they lure and trap within their webs before encasing them in cocoons. When food supplies in their environment are insufficient, these spiders travel to other webs and pretend to be trapped insects. As the other spider attempts to catch and consume it, the cellar spider attacks the unsuspecting arachnid. They prefer to eat small moths, flies, mosquitoes and other insects or spiders that are found near their webs. Cellar spiders and their webs are usually found in dark and damp places, such as cellars, basements, and crawl spaces. They can also be found in the corners of garages, sheds, and warehouses, on eaves, windows and ceilings, and in closets, sink cabinets and bath-traps. Although, cellar spiders do possess fangs and there is a legend that they have the most potent venom of any spider, the length of these fangs are too short to penetrate human skin, therefore they are harmless to us.
The Green Orb-Weaver Spider (5-7mm in length), as the name suggests, has a bright green abdomen and a yellow or reddish coloured head. Just above the spinners (the tail end) it has a bright red spot. This is more obvious on young spiders and can only be seen from underneath the spider. Freshly hatched spiderlings are red, and change to brown before the autumn. Despite it’s almost fluorescent colour the Green Orb-Weaver Spider can remain very well camouflaged amongst vegetation. It is only when it strays from its normal habitat that it get noticed. It is a common native species that is found throughout the UK and northern Europe.
Members of this family of spiders (12-15mm long) are active hunters with good vision. The Nursery Web Spider hunts amongst low vegetation as well as on the ground. When detecting prey, they characteristically rest on vegetation with the first two pairs of legs together, held out at an angle. During courtship, the male Nursery Web Spider presents the female with a ‘nuptial gift’ in the form of an insect wrapped in silk. Until fairly recently, this gift was thought to protect the male from becoming the female’s next meal. Research has shown, however, that the gift entices the female to mate, and what’s more, the size of the gift is related to how long the female will mate with a male. The larger the gift, the longer copulation will last and so more eggs will be fertilized by more ‘generous’ males bringing larger gifts. Female spiders belonging to this family produce very large egg sacs, which they carry around beneath their body. When the time for the spiderlings to emerge approaches, the female deposits the egg sac on a leaf and spins a protective silk ‘nursery web’ around it. She then opens the egg sac slightly, and stands guard until the spiderlings emerge. These spiders are large, brown and hairy and are often confused with the Wolf Spider. Unlike the wolf spiders, which have two very prominent eyes in addition to the other six, the eyes of the nursery web spiders are more or less the same size. Many species are able to walk on the surface of still bodies of water, and may even dive beneath the surface for a time to escape enemies. These spiders are venomous & can bite you but they are not dangerous. There bite is similar to an ant bite resulting in some very mild swelling for a few days.