Guest Article for the Tallahassee Democrat
May 22, 2015
By: Kathy Kinsey
Arachnophobia! The fear of the eight legged ones – spiders….all spiders! But trust me on this – they are more afraid of you than you will ever be of them! For me, I simply can’t imagine my garden without them.
The Golden Silk Orb-Weaver (Nephila clavipes) and the Yellow Garden Spider (Argiope aurantia) are two spiders that thrive in our area and have been observed by most of us. Both have an uncanny ability to weave very interesting webs. The female of these two species are much larger and more colorful than the unassuming males. An interesting note – this is quite the opposite in the bird world for in their world, it is the males that sport all those bright and beautiful colors. So for this article, I would like to focus on the females of each of these spiders.
Commonly called banana spiders, the Golden Silk varies from reddish to greenish yellow in color. The contrasting colors on their legs of dark brown/black and green/yellow acts as a warning sign to repel any potential predators that might be looking for a quick meal. This is no small spider for it measures in size from 1 ½ inches to 2 inches – and this does not include the legs. Nephila is widespread in warmer regions all throughout the world as it has been seen in Australia, Asia, Africa and the Americas. N. clavipes is the one seen here in Florida and in the coastal southeast and inland areas from North Carolina to Texas. Nephila is the oldest surviving genus of spiders, with a fossilized specimen known from 165 million years ago.
Their name refers to the color of the silk they use in constructing their webs, not the spider itself. Shining like threads of sunlight, their web is hard to miss on a sunny day. The yellow comes from a Xanthurenic acid, two quinines and an unknown fourth compound. The silk’s color may serve a dual purpose – to ensnare bees that are attracted to the color and when constructed in a shady area, to act as camouflage. This spider first weaves a non-sticky spiral with a space for 2-20 more spirals in between and when she has completed the coarse weave, she will then fill in the gaps. Whereas most orb-weaving spiders will remove the non-sticky spirals, this one leaves them. The web is renewed regularly if not daily as the stickiness of the web will decline with age. When the weather is good, only a portion of the web may be rebuilt by the sub-adults and adults. The spider will remove and consume the portion of the web that is to be replaced. New radial elements are then weaved and then new spirals and before you know it, a new web is constructed. Their partial renewal of the web differs from other orb-weaving spiders in that the others usually replace the entire web. Molting occurs while the spider is on the web and these old “shells” can be seen hanging on the web. Their webs are normally seen in open areas such as the edge of a forest, fences and overhangs. She will oscillate her web at approximately 40 Hz when the web is plucked which is thought to be a response to a potential predator. Kind of like a human walking into it – then the next few minutes are spent making sure she is not in your hair!
The venom is potent but not lethal to humans. Containing venom similar to that of the black widow, it has a neurotoxic effect on their prey but it is not as powerful as that of the widow. Their bite will cause local pain, redness and blisters that normally disappear within a 24 hour period. If you are bitten and have any allergies, contact your doctor or seek medical assistance from the hospital. This spider can be seen in late spring until the first frost.
The Yellow Garden Spider is known to many as the Writing Spider. I grew up knowing it as this for the “writing” design in their web. This is a striking spider, as spiders go, with its coloration of black, white and yellow. Though not as large as N. clavipes, this is no light weight. She measures in at .75 – 1.10 inches – not including the legs. I also found this one was a little shyer than the other and would have preferred to not have its picture taken!
Commonly found in the United States, Hawaii, southern Canada, Mexico and Central America. They have a very distinctive web with a dense zigzag silk design in the center. Possibly acting as camouflage for the spider lurking in the center of the web, it may also attract insect prey or may even warn birds of the presence of the otherwise difficult to see web. This zigzag design is known as a stabilimentum and is only spun by spiders that are out during the day, though its purpose is under some debate. They can be found along the eaves of buildings and in any tall vegetation where they are protected from the wind which will allow a web to be securely attached.
In constructing the web, several radial lines are stretched among four to five anchor points that are three or more feet apart. These lines will have a central point and she will then fill the center with a spiral of silk. Making sure the web is tight she will bend the radial lines slightly together while applying the silk spiral. She normally hangs upside down on the web awaiting her prey. If she detects a predator, she will drop to the ground until the danger has passed. This web will normally remain in the same location for the entire summer – they will only move it if the location is not a good “hunting” one. This spider can also oscillate her web vigorously which might help prevent predators like wasps and birds from drawing a bead on her location. She will consume the circular interior part of the web each night and will rebuild it the next morning. The radial framework will remain as is. Webs are kept clean and free of debris unlike those of the orb spiders. Keep in mind any spider or insect will bite if bothered or grabbed. Most spider bites feel like a bee sting accompanied by some redness and swelling. As with any insect bite, if you have allergies, seek immediate help. Their venom contains a library of polyamine toxins with potential as therapeutic medicinal agents.
Breeding only once a year, the male will seek out a female. When he finds the one of his dreams, he will build a web to be near her and will then court her by plucking the strands of her web. Just in case she attacks him, he builds a drop line. Safety first! After successfully mating her, he will then die and will sometimes be eaten by the female. Both spiders lay an egg sac – usually near or on the web which is encased in silk. Eggs sacs are quite huge ranging anywhere from half an inch to a full inch. She will guard this sac against predators for as long as she lives. As these spiders live on a web, cold weather affects them and they will become frail and eventually die. But hopefully, the young spiders will have exited the sac. Some will remain nearby while others will catch a breeze which will carry them off to another distant land. Small insects and vertebrates make up their menu. They do not seem to be too keen on grasshoppers but all others are most welcomed.
Spiders – they are not just something nightmares are made of – they do us a great service and by letting them hangout in your garden, you will be guaranteed a great source of bug control for years to come. But if she has built her web in an unwelcomed area, just wrap her and her web around a stick, lay the stick in an area where she can hangout, and walk away. Before you know it, she will have rebuilt her web and as a reward, will eat all those nasty things you don’t want.
Spiders – one of the Good Ones!
Kathy Kinsey is a Master Gardener volunteer with the UF/Leon County Cooperative Extension Office. You may also email us at Ask-A-Mastergardener@leoncountyfl.gov with any gardening questions you may have.