With summer coming to a close and fall on its way, this is the time of year we like to call spider season. Although spiders can be seen in any season, the large webs of orb weaver spiders really shine at this time of year. These spiders have been here since spring, but they grow into full adults with larger webs in August and September.
Orb weaver spiders are a part of the Araneidae family. It is a large, diverse group of spiders of many different colors, sizes and shapes. Spiders have two body parts. The “head” is called a cephalothorax, and the “bottom” is called an abdomen. Orb weavers usually have a large abdomen decorated with patterns. Nocturnal, or nighttime, orb weavers tend to be brown or gray to camouflage themselves. Diurnal, or daytime, spiders are brightly colored with oranges and yellows to stand out.
The spiders in this group are also known for their beautiful webs. Male orb weavers are much smaller than females and only spin a web when they are young. Once males reach maturity, their only focus is finding a female to mate with while also becoming her dinner.
The big webs most often seen out and about are made by the females. Think back to the famous story “Charlotte’s Web.” Charlotte spun something new every night. The straight spokes of the web are not sticky. They are used as a path for the spider to move around. Then she will add in the circular strands. These strands are sticky and will trap any insect on contact. After the web is complete, the orb weaver finds a hiding place on a nearby leaf or branch. When she feels any slight vibration, the spider will check the web for any catches.
These spiders like to be anywhere they can find insects. They can be in the forest, using tree branches for the webs, or in the tall grasses and flowers in the prairie. You could even be lucky to spot one using the structures around your house, like windows, lights and awnings.
If you do come across one, there’s no need to worry! These spiders are gentle and will flee when they see large humans approaching. In fact, seeing one is a great sign because they are catching and eating many insects we think of as pests.
Here’s more information on three common orb weavers we see in the forests preserves.
Black and yellow Argiope (Argiope aurantia)
This black and yellow spider goes by many names: black and yellow Argiope, yellow garden spider, golden orb-weaver and zipper spider to name a few. The females’ bodies grow to a little over an inch long, not including their long legs. They are most active during the day.
They spin a zigzag structure in the middle of their web called a stabilimentum. Scientists are still debating what this feature is used for. Some think it gives the web more stability, while others think it may alert birds to the web so they don’t crash into it.
Marbled orbweaver (Araneus marmoreus)
Marbled orbweavers can vary in color, with yellow to orange oval abdomens marked with brown or purple marbled patterns. They can be just shy of an inch long. They use a wide variety of habitats, but they prefer to be close to wetter areas.
These spiders make their webs during the morning and then hide out in a leaf that they curl and fold over themselves with their silk. When nighttime hits, they will sit in the middle of the web waiting for prey.
Spined micrathena (Micrathena gracilis)
The smallest of our three common orb weavers, the spined micrathena measures less than half an inch. It has pointed spines or ridges on its abdomen, and these are thought to make it harder to be eaten by a larger predator. It has black, brown and white patterns to help it blend in with the shadows of the forest.
Spined micrathenas prefer to build webs in denser forests, using trees and branches for support. Some webs can span about 6 feet long, going from one tree to another or even across trails.
Level up your spider knowledge
All these common orb weavers can be found along the trails in our preserves. Keep an eye out for their dazzling webs and see if you can find the spider hiding out nearby. Want to learn more about spiders? Join Forest Preserve District naturalists for our upcoming programs:
Spider “Sniffing” Hike: 7 to 9 p.m. Tuesday, September 14, at Plum Creek Nature Center. All ages.
Spider Eyeshine Hike: 7:30 to 8:30 p.m. Friday, September 17, at Isle a la Cache Museum. Ages 6 and older.
Nature Play Day: Spiders: 10 to 11:30 a.m. Wednesday, October 13. For children ages 3 to 5.
Interested in other Forest Preserve District programs? Check out our event calendar.
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