Spider eggs and egg sacs

You may have seen spiders scurrying around inside or outside your property, but chances are, you haven’t thought much about where these spiders come from - namely, their eggs. 

But how do spiders lay eggs? Take time to learn more here about spider egg sacs, the eggs of some different kinds of spiders, and how to get rid of spider eggs. If you’re concerned about spiders inside your property, reach out to Western Exterminator at 800-937-8398 or contact us online to have an expert spider exterminator take a look at the problem.

Do spiders lay eggs?

Yes, spiders lay eggs. After female spiders mate with males, they keep sperm in a holding place so they can fertilize the eggs. They fertilize the eggs right before laying them.

How do spiders reproduce?

Spiders reproduce sexually, with male spiders transferring sperm to females using specialized structures called pedipalps. After mating, females store the sperm and use it to fertilize their eggs before laying them. Some species perform elaborate courtship rituals to prevent males from being mistaken for prey. Such species include jumping spiders, wolf spiders, and orb-weaving spiders, to name a few.

Where do spiders lay their eggs?

Spiders lay their eggs in secure locations - nests - that offer protection from predators and environmental threats. Many species deposit their spider egg sacs in hidden spots like the underside of leaves, in crevices, or within their webs, which they spin with parts of the body called spinnerets. Some spiders, such as nursery-web spiders and wolf spiders, carry their egg sacs with them for added protection. Trapdoor spiders might lay them inside of a burrow for protection.

How many eggs do spiders lay?

Female spiders can lay anywhere from a few dozen to over 3,000 eggs in their lifetime, depending on the species. These eggs are typically wrapped within silk sacs, each containing between 30 and 300 eggs. For example, the common house spider (Parasteatoda tepidariorum) may produce up to 17 sacs, totaling more than 4,000 eggs over its lifespan.

Not all spiders lay eggs the same way. Some, like wolf spiders, carry their sacs on their bodies. Others, like cellar spiders, transport them in their jaws. Depending on environmental conditions, the hatching period can range from a few weeks to several months. 

Despite the high number of eggs laid, only a small fraction of spiderlings survive to adulthood, as many are eaten by predators or don’t survive due to various environmental factors, like the weather.

Do all spider species lay the same number of eggs?

How many eggs spiders lay depends on their size, habitat, and survival strategies. While some species lay just a few dozen, others can produce spider egg sacs containing hundreds or even thousands of eggs. And it’s not necessarily the big spiders that lay more eggs. For instance, black widow spiders can lay around 300 eggs per sac, whereas wolf spiders lay fewer but actively protect them. Huntsman spiders might lay 200 to 300 at a time, garden spiders usually lay 300 to 1,000 eggs, and house spiders might lay 150 - 400 eggs multiple times. Environmental factors also influence how many eggs a spider produces.

Spider egg sac

Typically, spider eggs are contained in a silken sac, which guards the eggs from predators as well as changing temperatures. An egg sac can be larger than the actual spider. Spider egg sacs don’t all look alike - they may be flat or round or look like something else, and they can have varied colors such as brown or white.

How do spiders protect their egg sacs?

The cocoon can be located in the soil, hung in a web, held to a leaf, or found elsewhere. Long-bodied female cellar spiders usually transport their egg sacs between their jaws until the eggs hatch. Other spiders - like the wolf spider, for instance - also tote their egg sacs. Nursery-web spiders carry their egg sacs as well and create a spot for their egg sac to rest when the eggs are close to hatching. Spiders that yield multiple cocoons have an inclination to desert them. Spiders will also protect their eggs aggressively if needed, striking at predators with their fangs.

What predators eat spider egg sacs?

Many predators target spider egg sacs, including birds, ants, wasps, and other species of spiders. Certain parasitic wasps lay their eggs inside the sacs, and their larvae consume the spider eggs from within. Rodents and some small mammals may also eat spider egg sacs if they come across them in their environment. The location of the sac plays a role in its vulnerability—those hidden in crevices or attached to webs have better protection than those exposed on leaves or the ground.

Read about the egg sacs of a couple of spiders below. If you are seeing spider egg sacs around your home and have concerns, contact Western Exterminator.

Black widow spider eggs

You may have heard about the symptoms of a black widow spider bite. But how much do you know about black widow spider eggs? Female black widows put eggs in silk egg sacs that have a diameter of about ⅜ to ½ an inch. Western black widow spider egg sacs are yellowish in color and are shaped like teardrops. But how many eggs do these spiders lay? Their sacs typically have about 300 eggs. The redback, a close relative of the black widow, produces similar egg sacs.

Brown widow spider eggs

Brown widow spiders are grayish-brown or brown in color. Their egg sacs are yellow in color, round and have silk spikes, in contrast to western black widow spider egg sacs, which are smooth. The spikes give the brown widow spider egg sacs a distinguishable look. The brown widow spider lays about 120 to 150 eggs in each sac. It has the ability to create approximately 20 egg sacs during its life.

Spider eggs hatching

The young spiders may not hatch for weeks. Some spiderlings remain in eggs during the winter and hatch in the spring; others hatch in a shorter period of time.

Spiderlings leave the sac after molting. At this time, they are pale in color. Actually, it is possible at times to view evidence of the first molts in the egg sac under a magnifying glass. In a phenomenon known as ballooning, the early-stage spiders in many species climb to a high spot and float onto the wind on silk threads in order to disperse.

Most spiders take about a year to become adults. They undergo roughly four to 12 molts before becoming mature. Compared to females, males typically go through fewer molts - they have smaller bodies.

Are spider eggs harmful to humans?

Spider eggs themselves are not harmful to humans, as they do not bite or carry diseases. But if spiders lay eggs inside a home or business, a large spider infestation could develop once they hatch. Certain spider species, like black widows and brown recluses, pose a threat if the hatched spiders mature and bite when disturbed. If you find spider egg sacs, it's best to remove them promptly to prevent an increase in the spider population.

How to get rid of spider eggs

If you spot spider eggs in your home or business, they should be removed. One option is to use a vacuum to remove spider egg sacs. Make sure to shut the bag and take it outside right away. But if spiders have overrun your property, or you’re simply concerned about the presence of a few of these pests, you can rely on Western Exterminator’s professional spider removal and control.

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