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Common Spider Species
The vast majority of spiders found in Ireland are completely harmless and are not considered to be pests.
Spiders play a highly important role in our ecosystem because they help rid your home and garden of unwanted flying insects. If you see one inside your house, the best approach is to carefully trap it using a glass and a piece of paper or card to move it safely outside.
While there are thousands of spider species around the world, there are only about 380 species found in Ireland. Out of these, you will likely only ever encounter a handful inside your home, garage, or garden.
Find facts below about the habits, lifecycle and bites of some spider species.
False Widow Spider
(Steatoda)
False Widow spiders only bite in defence if they feel threatened.
Appearance
- Brown bulbous abdomen with pale markings – females grow to 15mm.
Life cycle and habits of a False Widow Spider
Habits
- Hangs upside down from ‘tangle webs’ in dark corners.
- Closely resembles the black widow spider.
- The web is typically a random scaffolding of threads.
- Natural habits include low vegetation and undisturbed areas.
- In urban environments they occur in unused sheds, outbuildings and indoors.
- Bites are fairly rare and only occur when the spider is feeling threatened, they localised short term pain and swelling.
Wolf Spider
(Trochose Ruricola)
Wolf spiders hunt at night but spend the day hidden amongst moss and decaying matter.
Appearance
• Adult female: 8 mm; male - 6 mm. They are generally brown to grey in colour.
Life cycle and habits of a Wolf Spider
Life Cycle
- Wolf spider mothers carry their egg sacs around with them attached to spinnerets under the abdomen.
- When the young spiderlings hatch, they climb onto their mother's back where they live for the first few weeks of life.
Habits
- They live in a shallow burrow, with an open and unadorned entrance.
Harvestman Spider
(Phalangium Opilio)
Harvestman spiders can be found in fields and forests.
Appearance
- Adult – 3.5–9mm body. The upper body surface has light grey/brown pattern, the lower surface is typically cream.
Life cycle and habits of a Harvestman Spider
Life Cycle
- The females lay eggs in moist soil.
- The eggs survive through winter and hatch in the spring.
- Only one batch of eggs is laid each year.
Habits
- They climb tree trunks or look for food on the ground.
- They feed on many soft bodied arthropods, including aphids, caterpillars, beetle larvae, and small slugs.
Common House Spider
(Family Diaspidae)
Common House spiders can be found in your home or business.
Appearance
- Adult – body length excluding legs 6 – 10mm. Yellow brown body with faint markings. Abdomen pale grey brown with short hairs.
Life cycle and habits of a Common House Spider
Life Cycle
- The egg sac produced by the female is spherical, covered with a layer of silk and placed within the web structure.
- The male will mate several times with the female before dying.
- Adults may live for several years.
Habits
- Found in buildings, sheds and walls.
- This spider produces a sheet web.
Cellar Spider
(Pholcidae)
The cellar spider is sometimes known as the daddy longlegs spider. It gets its name due to primarily being found on the ceilings of rooms or cellars
Appearance
- Adults 2.5cm, four long pairs of legs and two body parts.
- Very long, thin legs.
- Will rapidly shake its body on the web when disturbed.
Life cycle and habits of a Cellar Spider
Habits
- Diet primarily consists of insects.
- Breed at any time of the year – not affected by seasons.
- They catch and eat other insects.
Yellow Sac Spider
(Cheiracanthium)
Adult Yellow Sac spiders can be seen from April through November. They emerge at night to look for food. They drop to the floor to seek cover when disturbed.
They are likely to enter homes during early Autumn when their outdoor food supply decreases.
Appearance
- Pale in colour, abdomen can be yellow or beige with a faint dark stripe running lengthwise.
- 1/4 to 3/8 inches long.
- 4 pairs of legs, the 1st pair longer than the 4th.
- Eight similarly-sized dark eyes arranged in two horizontal rows.
Life cycle and habits of a Yellow Sac Spider
Life Cycle
- A female produces around 5 egg sacs each with 30 to 48 eggs. The female may produce several egg masses during her lifetime.
- Eggs are laid in autumn.
- Spiderlings emerge the following spring.
- Approximately 30% of adult males get eaten by females after mating.
Habits
- Feeding - usually small insects.
- Location – They build a silken tube or sac (instead of a web) in a protected area which is used as their daytime retreat.
- Externally this can be within a leaf or under logs; Indoors this can be or at the junction of a wall and ceiling or behind pictures and shelves. They are normally outdoor spiders, but will set-up indoors if there are small insects available and are found on walls and in corners close to the ceiling, they drop from ceilings on silk threads.
Brown Recluse Spiders
(Loxosceles Reclusa)
Brown Recluse spiders are often called ‘fiddleback’ or ‘violin’ spiders because of the violin-shaped marking on the top surface which points from the head area toward the abdomen.
Appearance
- 1/4 to 3/4 inch long.
- Brown or deep yellow colour.
- Long, thin, brown legs covered with fine hairs.
- Six eyes, arranged in pairs in a semicircle.
Life cycle and habits of a Brown Recluse Spider
Life Cycle
- Eggs are laid primarily from May to July.
- The female lays about 50 eggs in an off-white silky sac approx. 2/3 inch diameter.
- Spiderlings emerge around 1 month later.
- It takes on average one year to reach the adult stage.
- Adults can live 1-2 years.
Habits
- Locations - They prefer secluded, dark, undisturbed sites indoors or outdoors. Indoors, they may be found in attics, basements, closets, ductwork, in storage boxes, shoes or behind furniture. Externally they may be found in barns, storage sheds, garages, under logs, loose stones and stacks of lumber.
- Feeding - They prefer dead insects.
- They can survive about 6 months without food or water.
- Visibility - The sac serves as the spider's daytime retreat. They tend to look for food at night.
Spider Species: Frequently Asked Questions
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What spiders are common in Ireland?
The most common spiders you will encounter in Irish homes and gardens include the Common House Spider, the Cellar Spider (often called the daddy-long-legs spider), the False Widow, the Wolf Spider, and the outdoor Harvestman. During the autumn months, the Giant House Spider also frequently moves indoors in search of a mate.
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Are there poisonous spiders in Ireland?
While almost all spiders use venom to submerge their insect prey, Ireland has no native spiders that are dangerously poisonous to humans. The Noble False Widow, which has established itself across Ireland, can deliver a bite that causes localized pain and swelling similar to a wasp sting, but it is not considered life-threatening unless an individual has a rare allergic reaction.
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What is the biggest spider in Ireland?
The biggest spider in Ireland is the Giant House Spider (Eratigena / Tegenaria species), which can reach a staggering leg span of up to 12cm. These massive brown spiders are completely harmless and are most frequently spotted darting across living room floors or trapped in sinks during the autumn breeding season.
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What is an October spider?
The term "October spider" is a common nickname in Ireland for the large house spiders or garden spiders that seem to suddenly appear everywhere in mid-to-late autumn. This sudden visibility happens because adult male spiders leave their hidden webs and actively wander into the open areas of your home to search for females.
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Can spiders bite you in Ireland?
Yes, some spiders in Ireland can bite you, but it is a very rare occurrence because their tiny fangs usually cannot pierce human skin. Species like the False Widow or the Yellow Sac spider will only bite as a last resort if they are accidentally trapped against your skin or crushed inside clothing, and their bites typically cause only mild, temporary irritation.
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Will sleeping with lights on keep spiders away?
No, sleeping with the lights on will not keep spiders away because they are not repelled by light. In fact, leaving lights on can inadvertently attract flying insects like moths and flies into your room, which provides an abundant food supply that will draw hunting spiders closer to your bed.