Egg Sacs, Spiderlings And Dispersal - The Australian Museum

Skip to main content Skip to acknowledgement of country Skip to footer

On this page... Toggle Table of Contents Nav

• Egg sacs, spiderlings and dispersal
• Egg sacs and maternal care
• Spiderlings and dispersal

Find out how spiders protect their eggs and how the newly hatched spiders make their way into the world.

Egg sacs and maternal care

The egg sac silk protects the eggs against physical damage and excessive drying, wetting or heating, as well as providing a shield against predators like ants and birds. However, this protection is often breached by parasitic wasps, flies and mantispid lacewings that succeed in laying their eggs or infiltrating their larvae among or within the spider's eggs. Spiders like redbacks lay many eggs and make several egg sacs to ensure that enough eggs survive these seasonal onslaughts.

The eggs of many spiders are glutinous and stick together allowing them to be laid in a continuous stream into the partly built silk egg sac. They vary in colour from pearly white to green and in number from 4 to 600 in a single egg sac, depending on the species concerned.

Egg sacs come in all shapes, sizes and colours. They may be built inside a burrow (e.g, trapdoor spiders), under bark (e.g, huntsman spiders), in the web (e.g., black house spiders), in a curled leaf (e.g., leaf curling spiders), suspended on a long line (two-tailed spiders), or hidden among foliage (e,g., orb weaving spiders). Some spiders stay with the egg sac, guarding it until the spiderlings emerge (e.g, huntsman spiders, trapdoor spiders) or carry the egg sac about with them (wolf spiders, water spiders), sometimes in their jaws (daddy-long-legs spiders). Wolf Spiders carry their spherical egg sacs slung from the spinnerets. When the young hatch they climb onto the mother's back, clinging to special knob-shaped hairs. The mother carries them about until they moult and disperse.

In many species, like orb weaving spiders, the egg sacs are simply abandoned, sometimes protected among leaves or in silk barriers, or even shallowly buried in soil (Nephila pilipes). Exposed egg sacs usually have a surface silk layer of dull brown, green or russet coloured silk, often further camouflaged with leaf debris to help prevent eggs being eaten or parasitised.

Spiderlings and dispersal

After hatching from the eggs the spiderlings stay within the egg sac until they undergo their first moult - their small cast skins can be seen inside the old egg sac. After this they emerge, having cut a neat hole in the sac with the fangs (perhaps aided by a silk digesting fluid and sometimes helped by the female from outside). The spiderlings cluster together initially, still living largely upon the remnants of yolk sac in their abdomens.

After several days (or weeks in the case of some mygalomorph spiders) and sometimes another moult, the spiderlings begin to disperse gradually away. This is necessary to avoid competition for food and prevent cannibalism among the hungry siblings. Some species, especially ground and burrow dwellers, disperse by walking, often over only relatively short distances. Others, especially foliage dwellers and many web builders, but also wolf and mouse spiders, disperse by bridging and ballooning. Bridging is a means of travelling by repeated climbing up through foliage and then dropping down on a silk line to cross to adjacent branches, often with some breeze-assisted swinging. Ballooning involves ascending to a high point on foliage and letting out fine silk lines that catch the breeze and eventually gain enough lift to waft the spider up and away. While long distance flights can occur (Charles Darwin noted spiderlings landing on the rigging of the Beagle, 100 km out at sea), the more usual outcome is for spiders to be deposited anything from a few metres to a few kilometres from the start point.

Simultaneous ballooning by thousands of spiderlings can result in a remarkable carpet of silk, called gossamer, covering shrubs or fields.

Having survived the perils of wasp, fly and mantispid lacewing egg parasitism in the egg sac, the life of spiderlings remains beset with dangers. Only a few will avoid being eaten and find adequate shelter and food to ensure their survival to adulthood, so any help is useful. The first orb webs of St Andrew's Cross spiderlings have a 'doily'-like patch of white silk at the centre which may be both attractive to insect prey and provide a 'hide' for the spider to disappear behind when predators appear. Some spiderlings simply don't leave home and grow up in communal webs and dispersing just before maturing (e.g., Phryganoporus candidus). Sticky web building spiderlings can partly support themselves simply by eating their own webs. Sticky webs like orb webs pick up valuable nutrients such as pollen grains that simply get windblown onto them - and, because sticky silk absorbs moisture from the air, which also condenses as dew on silk lines, the spiderling gets a drink as well.

Back to top of main content Go back to top of page

Also in this section

• Wood or Forest Scorpion Cercophonius squama
• Spider webs
• Spiders in West Africa
• Scorpions Urodacus spp.
• Swift Spiders, genus Nyssus
• St Andrew's Cross Spider Argiope keyserlingi
• Spiders in the House and Garden
• Daddy-long-legs Spider Pholcus phalangi
• Sac Spiders Clubionidae
• Cupboard Spiders Steatoda sp.
• Magnificent Spider Ordgarius magnificus
• Ground Spiders Anzacia

You may also be interested in...

Sac Spiders

Sac spiders are found throughout Australia in forest and grassland habitats.

Clubionidae Discover more

Wolf Spiders

Wolf Spiders are found throughout Australia. They are robust, agile hunters that live on the ground in leaf litter or burrows. They are often found in lawns and gardens.

Lycosa furcillata Discover more

Some notes on rearing Poltys (Araneae: Araneidae) in captivity

AM Publication Read more

Spiders

Learn more about spiders, their origins, and how they are classified. Discover factsheets from the Arachnology collection, which includes the largest collection of funnel-web spiders in Australia.

Spider diversityDangerous spidersFactsheets Learn more

Black House Spider

Black House Spider is common in urban areas, and is sometimes called the Window Spider.

Badumna insignis Discover more

Red-headed Mouse Spider

Red-headed Mouse Spiders have a smooth, glossy carapace and their head area is high, steep and broad with very large, bulbous jaws.

Missulena occatoria Discover more

Huntsman Spiders

Australian Huntsman spiders belong to the Family Sparassidae (formerly Heteropodidae) and are famed as being the hairy so-called 'tarantulas' on house walls that terrify people by scuttling out from behind curtains.

Sparassidae Discover more

Rufous Net-casting Spider

These slender, long-legged spiders have eight eyes, two of which are enormously enlarged and face forwards, looking rather like searchlights.

Deinopis subrufa Discover more

Slater-eating Spider

The introduced Slater-eating Spider, has a strong aversion to ants, which may help to limit its distribution in Australia.

Dysdera crocata Discover more

Foliage Webbing Spider

Young Foliage Webbing Spiders delay their dispersal and live together in communal nests built on plant foliage until they reach the subadult stage.

Phryganoporus candidus Discover more

Garden Orb Weaving Spiders

The commonly seen Garden Orb Weavers are stout, reddish-brown or grey spiders with a leaf-shaped pattern on their fat, roughly triangular abdomens, which also have two noticeable humps towards the front.

Eriophora biapicata Discover more

Garden Wolf Spider

Wolf spiders are robust, agile, fast-moving ground hunters that chase down or ambush prey.

Tasmanicosa godeffroyi Discover more You have reached the end of the main content. Go back to start of main content Go back to top of page Back to top You have reached the end of the page. Thank you for reading.

The Australian Museum respects and acknowledges the Gadigal people as the First Peoples and Traditional Custodians of the land and waterways on which the Museum stands.

Image credit: gadigal yilimung (shield) made by Uncle Charles Chicka Madden

Close modal dialog Search website Submit Search Close Modal Dialog Close Modal Dialog Close Modal Dialog Close Modal Dialog