Do Spiders Lay Eggs?
Yes, spiders do lay eggs. Female spiders produce eggs that are usually enclosed in a protective silk case called an egg sac. The number of eggs per sac varies widely depending on the species—from just a few dozen to several hundred or even over a thousand in some cases. The female often guards the egg sac or attaches it to a secure surface, such as a web, plant, or crevice, to protect it from predators and environmental hazards.
Once the eggs hatch, spiderlings emerge, which are essentially miniature versions of adult spiders. In many species, the spiderlings stay near the egg sac for a short period before dispersing. Some species even exhibit maternal care, with the female carrying the egg sac or young spiderlings with her for added protection.
The reproductive cycle of spiders is highly adapted to their environment, ensuring that even with high predation rates, enough offspring survive to adulthood.
Spider Egg Sacs
Knowing what spider egg sacs look like is important for several reasons:
Assessing Infestation Levels: Spotting egg sacs allows you to estimate the potential spider population in an area. One egg sac can contain dozens or hundreds of spiderlings, so identifying and removing them early can prevent a significant infestation.
Prevention of Spread: Spiderlings can disperse widely once they hatch. Identifying egg sacs early helps contain the spread of spiders to other parts of a home, garden, or building.
Targeted Control Measures: Knowing what the egg sacs look like enables you to remove or treat them effectively. Some egg sacs are attached to hidden locations like under eaves, inside garages, or in corners. Recognizing them helps ensure that control methods (physical removal, insecticides, or barriers) are applied where they will be most effective.
Some spider species produce venomous adults. Removing egg sacs before hatching reduces the risk of accidental bites to humans or pets, especially in areas where venomous spiders are common.
What Do Spider Egg Sacs Look Like?
Spider egg sacs can vary widely depending on the species, but there are some common characteristics and visual cues you can use to identify them:
Shape and Size: Most egg sacs are spherical or oval, though some can be more elongated or irregular. Sizes range from a few millimeters to over 2 centimeters in diameter.
Color: Freshly made sacs are usually white, cream, or pale yellow. Older sacs may turn tan, brown, or gray as they age and dry out.
Texture: Egg sacs are made of silk, so they often look fuzzy, smooth, or papery depending on the species. Some are fluffy or woolly, while others are compact and tightly woven.
Attachment: Egg sacs are usually attached to a surface—like webs, under eaves, in corners, or in hidden crevices. Some species carry the egg sac with them on their abdomen until the spiderlings are ready to hatch.
Clusters: Some spiders produce a single sac; others may produce multiple sacs over a season. Inside the sac, dozens to hundreds of tiny spider eggs are packed tightly together.
Visually, if you see a small, silk-covered, ball- or oval-shaped object attached to a web, plant, or sheltered surface, there’s a good chance it’s a spider egg sac. Handling them carefully or identifying the species before removing them is important, especially in areas with venomous spiders.
Are Spider Egg Sacs Hard?
Spider egg sacs are generally not hard; they are made of silk and have a soft to slightly firm texture. The exact feel depends on the species and how densely the silk is woven:
Soft and fluffy – Some cobweb spiders and orb-weavers produce sacs with a loose, woolly silk that feels soft to the touch.
Firm or papery – Other species spin tightly woven sacs that are somewhat firmer, almost like thin paper, but still not truly hard.
Environmental effects – Older sacs that have dried out may feel stiffer or more brittle, giving the impression of hardness, but they remain fragile.
So, while some sacs may feel a little firm, they are never truly hard like a shell. They are designed to protect eggs but still allow spiderlings to emerge when ready.
What Shape Are Spider Egg Sacs?
Spider egg sacs can take a few different shapes depending on the species, but the most common are:
Spherical (round) – The most typical shape, seen in many spiders such as orb-weavers and cobweb spiders. These look like small, smooth or slightly fuzzy balls of silk.
Oval (elliptical) – Some spiders produce egg sacs that are elongated rather than perfectly round, giving them an oval or capsule-like appearance.
Irregular or amorphous – A few species create sacs that don’t have a uniform shape, often depending on where they are attached or how the female spins the silk.
Round and oval are by far the most common shapes, while irregular shapes are less frequent and usually species-specific.
Are Spider Egg Sacs Round?
Yes, most spider egg sacs are round or nearly spherical. This shape helps protect the eggs inside and makes the sac easier to suspend in webs or attach to surfaces.
Some species produce oval or slightly elongated sacs, but perfectly irregular shapes are uncommon. In general, if you see a small, silk-covered, ball-like structure in a web, crevice, or on foliage, it’s very likely a spider egg sac.
What Size Are Spider Egg Sacs?
Spider egg sacs vary in size depending on the species, but generally they fall within these ranges:
Small sacs – Around 3–8 millimeters in diameter. Common for tiny spiders like some cobweb species.
Medium sacs – About 1–2 centimeters (10–20 mm). Typical for many orb-weaver and garden spiders.
Large sacs – Up to 3 centimeters or more, produced by bigger species such as some tarantulas or large wolf spiders.
The number of eggs inside usually correlates with the sac size: small sacs may contain a few dozen eggs, medium sacs a few hundred, and large sacs several hundred to over a thousand.
Placement can also affect perceived size; sacs pressed against surfaces or tucked in webs can look smaller than they actually are.
How Big Are Spider Egg Sacs?
The size of a spider egg sac depends on the species, and the largest sacs come from big spiders, especially those that produce many eggs.
Typical large sacs: Many common orb-weavers or garden spiders produce sacs around 2–3 centimeters (about 0.8–1.2 inches) in diameter. These can contain several hundred eggs.
Extra-large sacs: Some wolf spiders or tarantulas can produce sacs exceeding 5 centimeters (about 2 inches) in diameter. These may hold several hundred to over a thousand eggs.
Exceptionally large species: Certain tropical or large tarantula species can produce sacs that are even bigger, sometimes up to 7–8 centimeters (around 3 inches) across, though this is rare and generally seen in wild specimens rather than typical household spiders.
So, the absolute largest spider egg sacs in nature are produced by the biggest spiders, particularly tarantulas, while most household or garden spider sacs remain under 3 cm.
How Small Are Spider Egg Sacs?
Spider egg sacs can be quite small, especially for tiny spider species. Typical ranges are:
Very small sacs: About 3–5 millimeters in diameter. These are common for small cobweb spiders or other tiny household spiders.
Small to medium sacs: Around 5–10 millimeters, seen in many common garden spiders and smaller orb-weavers.
Even though the sac may be tiny, it can still contain dozens of eggs, packed tightly together. Some of the smallest spider egg sacs are so inconspicuous that they can easily be mistaken for dust, debris, or small silk balls.
What Color Are Spider Egg Sacs?
Spider egg sacs can come in several colors, often influenced by species, age, and environmental conditions. Fresh sacs are usually light-colored (white, cream, pale yellow), while older or environmental-exposed sacs tend to darken to tan, brown, or gray.
Are Spider Egg Sacs White?
Yes, spider egg sacs are often white or cream-colored when they are freshly laid. This is the most common color for many species, including orb-weavers and cobweb spiders. The silk used to make the sac gives it a pale, sometimes slightly shiny appearance.
Over time, exposure to dust, sunlight, or environmental conditions can cause the sac to darken to tan, brown, or gray. So while white is typical for new sacs, older or weathered sacs may look quite different.
Are Spider Egg Sacs Brown?
Spider egg sacs can be brown, but this usually happens as they age or dry out. When freshly laid, most egg sacs are white, cream, or pale yellow, but exposure to sunlight, dust, or environmental conditions can cause them to darken to tan, brown, or gray.
Some species’ sacs are naturally a light tan or beige even when fresh, but a deep brown sac often indicates it is older or has been exposed for a while. So yes, brown is possible, but it is not the typical color for newly made sacs.
Are Spider Egg Sacs Black?
Spider egg sacs are generally not black. Most freshly made sacs are white, cream, or pale yellow, and some may turn tan, brown, or gray as they age or dry out.
A sac that appears black is usually:
Old and desiccated – The silk has darkened over time.
Dirty or covered in debris – Dust, soil, or other particles can make it look dark.
Species-specific – Very few spiders produce naturally darker sacs, and even then, pure black is uncommon.
So while a “black” sac can exist in certain circumstances, it’s not typical for healthy, recently laid spider egg sacs.
Where Are Spider Egg Sacs Found?
Spider egg sacs are usually placed in locations that offer protection from predators, environmental stress, and disturbance, and the specific placement often depends on the species. Common locations include:
Inside man-made structures – Garages, sheds, basements, attics, and other quiet, undisturbed areas are attractive to spiders for egg-laying, especially for species that thrive in human environments.
Sheltered crevices and corners – Egg sacs are often tucked into cracks, under eaves, behind furniture, or in wall voids. This protects them from wind, rain, and predators.
On plants or foliage – Some garden or orb-weaving spiders attach their sacs to leaves, stems, or branches, often camouflaged with silk.
Under debris or objects – Leaf litter, piles of wood, stones, or other debris provide hidden spots for egg sacs, particularly for ground-dwelling species like wolf spiders.
Inside webs – Many spiders attach their sacs directly to their own webs. Orb-weavers and cobweb spiders often suspend sacs among the web strands, sometimes in hidden corners.
Carried by the female – Certain species, like wolf spiders, carry the egg sac attached to their abdomen until the spiderlings are ready to hatch, so you may see the sac mobile with the adult spider.
The key pattern is that egg sacs are almost always in hidden or protected areas. Recognizing these common spots is essential for identifying infestations and managing spider populations safely.