Introduction
Cat-faced spiders are a type of orb-weaving spider found in North America. They get their name from the patterns on their abdomen that resemble a cat’s face. These spiders are medium-sized, with females reaching around 1 inch long while males are smaller at around 1⁄2 inch long. Cat-faced spiders are notable for building large, intricate webs. An interesting aspect of their biology is where and how they lay their eggs. This article will explore cat-faced spider reproduction, with a focus on egg sac construction and ideal egg-laying locations.
Description of Cat-Faced Spiders
The cat-faced spider (Araneus gemmoides) is aptly named due to the patterns on its abdomen that resemble a cat’s face, with two large eyes and a downturned mouth [1]. This medium-sized orb weaver spider has a round abdomen and long, spindly legs that span approximately 1 inch in diameter. Their bodies are mostly black or dark brown, while the “cat face” patterning can range from orange, yellow, to white [2].
Cat-faced spiders are nocturnal and build large, intricate wheel-shaped webs in between branches and vegetation. The web consists of sticky spiral capture silk and non-sticky radii lines that the spider uses for support and mobility across the web. They tend to rebuild new webs every day or two as the old web accumulates debris and damage. The spider will rest in vegetation or a rolled up leaf near the web during the daytime.
These spiders are widespread across North America and commonly found in gardens, woodlands, and scrublands. They usually construct their webs 1-3 feet off the ground attached to branches of shrubs and small trees. Cat-faced spiders play an important role in controlling insect pest populations.
Reproduction
Cat-faced spiders have a unique mating ritual. The male spider will approach the female’s web cautiously, tapping the threads to alert her of his presence. If she’s receptive, she’ll remain still while he climbs onto her web. The male will then cautiously approach and use his pedipalps to transfer sperm into the female’s epigynum (external genitalia). After mating is complete, the male will quickly retreat before the female attacks. Males typically die right after mating.
After mating, the female cat-faced spider can store the sperm for up to a year before using it to fertilize her eggs. The gestation period ranges from two to four weeks before the female is ready to produce an egg sac. She will lay anywhere from 100 to 2,000 eggs, depending on her size and health. The eggs are enclosed in a firmly woven silk sac that provides protection.
According to Bugwood, the female guards the egg sac for several weeks before the spiderlings emerge.
Egg Sac Construction
Cat-faced spiders construct their egg sacs in protected areas, often in a corner where a wall meets the ceiling or eaves of a building. The mother spider weaves a spherical silk egg sac, filled with a soft cushioning to protect the eggs. She attaches the finished sac to the protected area with strong webbing.
According to Bugwood, the mother spider constructs the sac by laying down a circular base of silk. She then fills the middle with soft fluffy silk cushioning. Once the cushioning is complete, she continues weaving the outer silk walls until the sac is fully enclosed in a protective sphere. The entire sac may be up to 2 inches in diameter when finished.
The egg sac construction process takes 1-2 weeks to complete before the mother spider starts laying her eggs into the finished sac, according to Outside Bozeman. The sac needs to be sturdy yet soft enough to expand as the eggs develop inside.
Ideal Locations for Egg Sacs
Cat-faced spiders prefer to construct their egg sacs in protected, hidden areas out of sight from predators. Common locations include under eaves, in corners of windows, under decks, and in sheltered crevices (Bugwoodwiki). They often build sacs in areas that provide stable temperature and humidity, helping ensure the eggs remain viable until hatching. Garages, sheds, barns, and other outbuildings frequently house cat-faced spider egg sacs thanks to the shelter and abundance of prey found there (A-Z Animals). Since the spiderlings will emerge from the egg sac in the same area, cat-faced spiders carefully select secluded egg sac locations to give their offspring the best chance of survival.
Egg Development
Female cat-faced spiders can produce hundreds of eggs in a single egg sac, though the exact number varies by species. Some research indicates the western black widow can lay up to 900 eggs per sac. Other sources note the southern black widow may produce 150-400 eggs at a time. The egg incubation period also varies but averages 20-30 days before the eggs hatch.
During incubation, the eggs initially appear off-white or yellowish in color. Over time they darken, eventually turning black right before the spiderlings emerge. Female spiders diligently protect and care for the egg sac during this vulnerable development phase. They instinctively know when the eggs are ready to hatch and will then tear open the outer silk layer. This allows the tiny spiderlings to escape the sac.
Proper temperature is critical during egg incubation. If conditions become too cold, development may be delayed or the eggs can die. Hot temperatures can also have detrimental effects. The female spider’s choice of egg sac location helps moderate conditions. Additional research is still needed to fully understand the intricacies of thermoregulation and mortality rates among cat-faced spider eggs.
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Hatching
Cat-faced spider eggs typically hatch in the spring or early summer after developing over the winter months. The length of time needed for the eggs to fully develop and hatch can vary based on temperature and other environmental conditions, but is often around 3-4 weeks.
When the spiderlings are ready to emerge, the egg sac ruptures open. The tiny spiderlings, known as spiderlings, crawl out of the old egg case and disperse. They do not stay together as a group or receive any care from the mother spider after hatching.
The process of hatching starts when the developing embryos have absorbed the yolk sac inside their eggs. The spiderlings secrete enzymes that allow them to break open and exit their eggs. They use a sharp structure called an egg tooth to help pierce the egg casing and work their way out. Once all the spiderlings have emerged, they immediately leave the old egg sac behind to start independent life.
Spiderlings go through multiple molts as they grow, eventually reaching adulthood after several months or up to a year. Their survival rates are very low, as they face threats from predators and environmental dangers. Only a small number from each egg sac will make it to maturity.
Spiderlings
After hatching from the egg sac, the cat-faced spiderlings are tiny, about 1-2mm in size. They are white to pale yellow in color and look very different from the adult spiders. The spiderlings remain together near the egg sac for some time after hatching.
The spiderlings do not disperse right away and continue to live together near the egg sac while they go through several molts. During this time, they do not build webs or capture prey. Instead, they live off the yolk reserves from their egg sac. After a few weeks and several molts, the spiderlings darken in color and start becoming more similar in appearance to the adults.
Once the spiderlings have gone through several molts over 4-6 weeks, they will finally disperse and leave the area around the egg sac. At this point they start behaving like juvenile spiders – building small webs, capturing tiny prey, and essentially living independent lives (Bugwood.org).
Threats
Cat-faced spiders face a number of threats, particularly at the egg and young spiderling stages. According to Bugwood, the egg sacs laid by female cat-faced spiders are vulnerable to predation by wasps, birds, and other spiders. The spiderlings that emerge are very small and lack the full venom potency of adults, making them easy prey for other spiders, insects, and birds.
Additionally, cat-faced spiders rely on finding suitable protected locations to spin their egg sacs. Destruction of habitats, pesticide use, and human activities can limit ideal spots and expose the egg sacs to predators and environmental factors like temperature extremes, heavy rain, or drought according to A-Z Animals. This threatens the survival of the next generation of spiders.
The threats are greatest during the egg sac and young spiderling stage. Once cat-faced spiders reach maturity, their venom, size, web-building abilities, and camouflage provide substantial defenses according to Bugwood. Their large size also makes them less vulnerable to predation from birds and other spiders. Still, habitat loss remains an issue for adult spiders as well.
Conclusion
In summary, cat-faced spiders have a unique reproductive process designed to help ensure the survival of the next generation. The females construct durable egg sacs using silk, carefully selecting protected locations out of harm’s way. Inside the egg sac, the eggs develop until hundreds of tiny spiderlings emerge. The spiderlings remain clustered together for some time before dispersing into the environment. Their diminutive size makes them vulnerable to predators, underscoring the importance of the female’s nest-building and egg protection efforts. With the right conditions, the young spiders will mature and the reproductive cycle begins anew.
