Garden spider egg sacs are papery, teardrop-shaped silk structures about half an inch to one inch in diameter, typically found suspended in or near the spider’s web in late summer and fall. Each sac can contain anywhere from 400 to over 1,000 eggs, making them one of the more impressive reproductive structures you’ll encounter in a backyard garden.
What a Garden Spider Egg Sac Looks Like
The yellow garden spider (the large black-and-yellow orbweaver common across North America) builds a distinctive egg sac that’s hard to miss once you know what to look for. It’s brown or tan, pear-shaped with a narrow “neck” at the top, and has a papery texture. The outer layers are made of tightly woven silk that feels surprisingly tough to the touch.
The female constructs the sac at night using a layered process. She first lays her eggs on a flat sheet of silk, then covers them with a different type of silk before using her legs to roll everything into its final rounded shape. The finished product looks a bit like a tiny brown paper lantern hanging from a thread. Some people compare them to miniature hot air balloons. The white, multilayered interior protects the eggs from moisture, temperature swings, and some predators.
Where You’ll Find Them
Female garden spiders attach their egg sacs to webbing near the center of the web, close to where the spider rests. They prefer to tuck them underneath vegetation or beneath the coverage of broad-leaved plants, which provides shelter from rain and direct sun. You might also find them hanging in the corner of a porch, tucked into shrubs, or anchored to fence posts and garden structures.
A single female produces one to four egg sacs in a season. Each one is suspended by strands of silk attached to nearby branches or structures. If you spot one egg sac, it’s worth checking the surrounding area for more, since the mother spider tends to place them in the same general vicinity.
How Many Eggs Are Inside
A single egg sac typically holds around 1,000 eggs, though the number can range from 400 to well over 1,000 depending on the spider’s size and health. Multiply that by up to four sacs per female, and one garden spider can produce several thousand eggs in a single season. That number sounds alarming, but it reflects the brutal math of spider survival: the vast majority of those offspring won’t make it to adulthood.
Overwintering and Hatching Timeline
Garden spider eggs hatch inside the sac in late fall, but the spiderlings don’t leave. They stay bundled together inside the protective silk casing through the entire winter, surviving freezing temperatures thanks to the insulating layers their mother built. The layered silk structure traps air and buffers against cold in much the same way a sleeping bag works.
When spring arrives and temperatures warm, the spiderlings chew their way out and begin dispersing. At this stage they’re tiny, roughly 1.2 millimeters long and barely visible to the naked eye. A large number won’t survive due to predation, weather, and competition, but enough will make it to populate your garden with orbweavers the following summer.
How Spiderlings Disperse
Newly emerged spiderlings use a remarkable technique called ballooning to spread out. A spiderling climbs to an exposed high point, like a blade of grass, twig, or fence post, and releases a strand of silk into the air. When the breeze catches it, the tiny spider lifts off and floats to a new location, sometimes traveling surprisingly long distances. This only works in gentle winds. Research on orbweaver spiderlings shows that at moderate wind speeds, nearly 90% of spiderlings attempted the behavior, but at higher wind speeds none of them tried, suggesting they can sense when conditions are right.
Some spiderlings use a variation called rafting, where they anchor a silk line to a plant and pay out more silk from the end of the strand until the wind provides enough lift. Either way, ballooning is why you might find tiny spiders appearing in parts of your yard far from where the original egg sac was located.
Relocating an Egg Sac Safely
If you find an egg sac in an inconvenient spot during fall garden cleanup, you can move it without destroying it. Use long tweezers or forceps to gently grip the sac and slowly pull it free from its anchor silk. Move carefully since the papery exterior is durable but not indestructible.
Place the sac in a dry, sheltered location like a garage, tool shed, or carport. You can set it inside a small paper bag to keep it contained. The key requirement is that the location stays dry and isn’t heated. The spiderlings need to experience the natural cold of winter inside their sac, and a warm indoor environment could trigger premature emergence when there’s no food available.
If the mother spider is still guarding the sac, try to relocate her along with it. You can gently guide her into a paper bag. She provides some early care to the spiderlings after hatching, and once they complete their first molt inside the sac, they become independent. By spring, the spiderlings will emerge and disperse on their own from wherever you’ve placed them.