How Long Does The Garden Spider Live After Laying Her Sack

A visit from the garden spider

This past week I noticed something other than Brussels sprouts in my garden — a beautiful garden spider!

I did what any curious entomologist and gardener would do… I got as close as I could and took a picture and watched in amazement as she sat and waited surrounded by meals in little to-go containers of silk in her web. A week later I stopped by to say my daily greeting to her and noticed she was gone, her web reduced to a single strand connecting my rosemary to my tarragon. And then something moved out of the corner of my eye… it was her… and she was building two beautiful egg cases about the size of ping-pong balls in my sage.

I shot a couple more photos and sent them off to spider expert Dr. Chris Buddle at McGill University in Montreal. He responded with a wonderful description of the natural history of my garden spider, and I had to share it with you here:

Argiope aurantia, or the 'black & yellow garden spider' is a truly magnificent orb-weaving spider. They are striking in their coloration, with bold black and gold patterning across their abdomens. We tend to notice these lovely animals in the late summer and early fall, because this is the time that they reach their full maturity, and therefore, their full size! They are certainly among the largest 'orb web spiders' that we can find in North America – with adult females reaching a body size of up to 3 cm (or just over an inch). Males are quite a bit smaller, and not observed as frequently as females.

After being fertilized, females will lay egg cases during the autumn months, and the eggs will overwinter within these egg sacs. In the springtime, tiny baby spiders ('spiderlings') will emerge from the egg case, and strike out on their own. We don't tend to notice these wee baby spiders, but they are in our backyards, gardens and fields, building small webs, and feeding on other invertebrates. As the summer progresses, the spiderlings grow up, and males and females reach maturity in the late summer.

Males will wander in search of a mate, and once found, and if copulation is successful, the fertilized female will eventually lay her egg case and the cycle will start again.

Argiope aurantia build magnificent webs in tall grass, shrubs, and often in our vegetable gardens. The spiders tend to sit in the middle of their webs, gently rocking back and forth as the autumn breeze passes through. As you wander through your garden, you will likely also notice that the webs are incredibly strong – they are build with a kind of 'cross brace', called a stabilimentum. The function of this kind of support is still disputed, but it's likely a combination of warning birds not to fly into the web (thus destroying the web and its contents!), for camouflage, or perhaps as a way to attract prey. Undoubtedly, Argiope aurantia is a spider that captures our imagination, and makes a bold statement in our gardens.

Next time you see one, stop for a while and watch. You just might catch a glimpse of some amazing biology, whether it's observing web-repair, feeding, or laying an egg case.

Thanks again, Chris, for the information and I'll be waiting until spring to cut down my sage so I can see the entire process take place!

Lea Shell is an entomologist and educator who devotes her time convincing others just how wonderfully important insects and microbes are to our lives. She enjoys playing with slime mold, ants, GPS units, climate loggers and interviewing scientists about their middle school experiences.