Argiope trifasciata (Banded Garden Spider)

Argiope trifasciata (Banded Garden Spider)

This is a large (body length 15-20mm for females; 4-6mm males) orbweaver (family Araneidae), with a silver carapace and banded legs and abdomen. The abdominal bands are usually narrow dark lines, with occasional thickened areas, against a white ground color with diffuse patches or bars of pale yellow. Males are roughly 1/3 the size of females, with a similar but less banded abdomen, and are much less likely to be found. There is really nothing similar in our region to the females of this species. 

The genus Argiope differs from other orb weavers by having it posterior middle two eyes behind the lateral eyes, rather than even with, or in front of, the lateral eyes. 

Argiope trifasciata

Members of this genus often have a transverse zigzag or bar going through the center of the web that is called a stabilimentum, the function of which is unclear. Studies have shown that Banded Garden Spiders tend to build their webs on an east/west axis, and to hang with their ventral side exposed to the south. Since much of their ventral surface is very dark it is believed that they do this to gather solar radiation. Studies also appear to show that webs built by mature Argiope trifasciata specifically target larger prey species. 

Dark ventral surface of a Banded Garden Spider

The eggs overwinter in an egg sack, which may contain 1,000 eggs, and hatch in the spring. The spiderlings disperse by ballooning. Maturity is reached in mid summer, and egg sacks are deposited in the fall. Adults do not survive the winter. 

Argiope, in Greek mythology, was a nymph who was the mother of the mythical bard Thamyris. And trifasciata means three banded. 

Eye arrangement of Argiope trifasciata

 I have had bad luck and/or pilot error every time I have found Argiope trifasciata in a web, dating back three years, to when I first started trying to get a photo of one of these beautiful spiders. Either I didn’t have a camera of any sort, or they were unreachable because of berry thickets, or I spooked them trying to approach so that they dropped and I couldn’t find them again. Or I ended up with cruddy pics due to uncooperative auto focus, wind on the web, or just a sheer lack of photography skills. So when I found these two in my sweep net I decided to take them home and cool them off and take a bunch of diagnostic photos. But I didn’t like the way those first photos turned out, so I turned them loose on the porch. And when I came home today I found one of them in my wife’s succulents, so I got some in situ photos anyway. 

Argiope trifasciata on my wife’s succulents

Size- Total body length females 15-20mm; males 4-7mm

Habitat- Open grassy and brushy areas

Range- Region wide 

Eats- Anything it can catch, but seems to target larger prey as an adult

Adult activity- Adults active from July to hard frosts

Banded Garden Spider
Dorsal view Argiope trifasciata
Ventral view Argiope trifasciata

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