Late Summer Spiders
August brings more than just heat and humidity to Harmony Hill. Along with many evenings spent watching lightning dance across the sky and, with any luck, the sound of rain falling on the landscape, we notice increased insect activity in the fields and forests. This increase in insect activity serves to fuel more than a few other species that feed on insects large and small. Whether it is the diminutive Blue-gray Gnatcatcher or slightly larger Acadian Flycatcher, we see birds working continually to dine on insects. Birds are not the only animals feeding while the bounty grows in the summer sun. Reptiles and amphibians eat their fill on fenceposts and along the edges of creeks. Other insects, like dragonflies and damselflies take part, as well. But, one of the most recognizable groups of animals are seen more and more this time of year, capturing insects and working to prepare for the next generation. As we walk in the woods and notice the days shortening ever so much each day, it is not uncommon to get a face full of spider web. The orb weavers are out, and we love seeing their artistry and bask in the utility of their beautiful work. There are many spiders at Harmony Hill, but this week, let’s look at two of the more eye-catching species we have.
Of the most skillful web builders found in the lower piedmont, these two species of spiders are certainly two of the most accomplished. The Giant Lichen Orb Weaver (Araneus bicentenarius) and the Marbled Orb Weaver (Araneus marmoreus) grab your attention immediately with their beauty and are each capable of constructing webs several feet in diameter. Both species have been observed at Harmony Hill and we expect to see them through early autumn.
Giant Lichen Orb Weavers are aptly named, as they are colored exactly like balls of lichen with eight legs. That is not by accident. They are found in wooded areas, much like the mixed pine-oak-hickory woods found throughout much of Harmony Hill. Many of these trees have green and gray lichens on their trunks and limbs, which look eerily like the colors and patterns found on (Araneus bicentenarius). Or should I say, the Giant Lichen Orb Weaver looks eerily like the lichens found on the trees in the woods it inhabits.
First described in 1888 by Rev. Henry McCook, a naturalist and Presbyterian pastor from Philadelphia, the Giant Lichen Orb Weaver is found from central Canada, south to Texas and over to the east coast of the United States. 1888 saw Philadelphia celebrating its own bicentennial and Rev. McCook was such an ardent Philadelphian that the species name of "bicentenarius" is a nod to the bicentennial of his favorite city.
The Marbled Orb Weaver is often referred to as the "Halloween Spider" or "Pumpkin Spider" by some. Being colored orange and black, it doesn't take a lot of imagination to see the resemblance this species bears to a Jack-o-lantern. The dark markings on the orange abdomen of the spider give us both the common name of "marbled" and the species name of "marmoreus", which is Latin for marble. The timing of seeing them in the forests of Harmony Hill also lends to the Halloween Spider nickname, as we begin seeing it in late summer and their numbers increase through very late summer. In early fall, and even all the way to the end of October, female Marbled Orb Weavers can be found in the forests; coinciding with that fabled fall holiday on October 31st.
Both species belong to the genus Araneus, which is taken from the Latin word for spider. While there are many types of orb weaving spiders (seriously... orb weavers compose a little better than 1/4 of all spider species), Araneus spiders are separated from other orb weavers by their rounded and/or angular "shoulders". But, the shoulders we're talking about are not in relation to any of their eight legs. Nope. These shoulders are protuberances, or bumps, on the abdomens of Araneus spiders. Take a look at the photos of the spiders from above and you can see the bumps on either side of the abdomen of the spiders. They appear to be more like dimples on the Marbled Orb Weaver, but are “shoulders, nonetheless.
Araneus spiders are not known for hanging out in the middle of their orbs during the day. Unlike their orb-weaving cousins, the Argiope spiders, who post up for all the world to see, Araneus spiders retreat to the seclusion and protection of a hideaway near their webs. These hiding spots may be clumps of dead leaves, exfoliating bark or anything else that will conceal it from potential predators.
When an insect enters the web, the Araneus spider will quickly leave its hideout and run down a dry escape line to subdue its prey. We all know how sticky spider webs can be, but have you wondered how they get that adhesion power? Well, it’s as simple as the silk being manufactured in four silk glands and then spun through six spinnerets. Then, the capture lines, those circular lines which comprise the hubs that go around and around the web, are coated with a glycoprotein as they are spun. That extremely sticky glycoprotein is also covered in an aqueous layer as it adheres to the capture lines being spun, allowing this capture lines to retain their adhesive properties as the web sits out in the drying conditions of the wind and sun.
The long, straight lines which radiate out from the center of the web and anchor the web to the structures it is built from are known as radial lines. They serve as the frame on which the orb can be built.
Much more common and noticeable in the fall of the year, these two spider species are harmless to humans and do a terrific job of consuming large numbers of insects during their lives. Both species lay eggs in the autumn of the year, with the young hatching in the spring of the following year.
Next time you’re out walking in the woods and you happen to get a web firmly planted to your face and head, instead of getting upset at the spider, remember you are in its home and it is serving a wonderful pest control function. And, if that spider happens to be a Giant Lichen Orb Weaver or a Marbled Orb Weaver, take a few minutes to soak up the beauty of the spider and the lovely web it has woven.
More on our orbweaver and spider friends at Harmony Hill in the coming weeks! There are so many more spider stories to tell!