Spider Egg Sacs: What to Do When You Find Them

Finding a spider egg sac can cause immediate alarm — the thought of dozens or hundreds of baby spiders hatching in your home is unsettling. The reality is more nuanced: most egg sacs found in Missouri homes belong to harmless species, and dealing with them correctly prevents the hatch from occurring in your living space. Here is what you need to know.

What Spider Egg Sacs Look Like

Egg sacs vary significantly by species:

• Orb weaver egg sacs: Often papery, yellowish to brown, found in vegetation or attached to exterior surfaces near webs. May be wrapped in leaves.
• Cellar spider egg sacs: Loose, irregular clusters of eggs held together with minimal silk, often carried by the female in her chelicerae (mouth parts).
• Wolf spider egg sacs: Round, white to tan, attached to the female's spinnerets — she carries the egg sac with her everywhere. After hatching, spiderlings ride on the mother's abdomen.
• Brown recluse egg sacs: White to off-white, papery, roughly spherical, approximately 1/3 inch in diameter. Found in secluded, undisturbed locations — inside cardboard boxes, in crawlspace corners, behind stored items. A single egg sac contains 40–50 eggs. Females may produce several egg sacs per year.
• Black widow egg sacs: White or tan, papery, pear-shaped, often with a rough texture, approximately 1/2 inch. Found in webs near ground level in garages, sheds, and under outdoor furniture.

How Many Spiders Are in an Egg Sac?

The number varies by species:

• Brown recluse: 40–50 eggs per sac
• Black widow: 200–900 eggs per sac
• Orb weaver: 100–300 eggs per sac
• Wolf spider: 100–400 eggs per sac
• Cellar spider: 13–60 eggs per cluster

These numbers sound alarming, but natural survival rates for spiderlings are very low — most do not survive to adulthood. That said, preventing egg sac hatch in your living space is clearly preferable to allowing it.

How to Safely Remove Egg Sacs

Outdoor and Exterior Sacs (Harmless Species)

For egg sacs on exterior walls, in garden vegetation, or in outbuildings — likely from orb weavers, grass spiders, or other harmless species — removal is optional. These spiders are beneficial and the hatch will occur outdoors where spiderlings disperse naturally. If you prefer to remove them for aesthetic reasons, brush or knock them down with a broom.

Indoor Sacs — Approach with Caution

For egg sacs found inside the home, particularly in basements, crawlspaces, or storage areas where brown recluses are a concern:

• Do not crush the sac with your bare hand — this can release spiderlings or, if the sac belongs to a brown recluse, expose you to the spider
• Use a vacuum to remove the egg sac — immediately empty the canister or bag outside in a sealed garbage bag
• Alternatively, seal the sac in a zip-lock bag by scooping it up and sealing — do not squeeze it
• If you can identify the sac as belonging to a harmless species (cellar spider, for example), a simple sweep or vacuum removal is fine
• If you suspect brown recluse or cannot identify the species, professional inspection is a prudent follow-up to find and address the harborage

The Larger Question: Why Are There Egg Sacs?

Finding multiple egg sacs — especially in multiple locations — indicates an established spider population that is reproducing successfully in your home. This points to the need for addressing the underlying conditions: reducing harborage, sealing entry points, and professional treatment of the affected areas. A single egg sac is not necessarily a crisis, but a pattern of egg sacs suggests a population management issue worth addressing proactively.