A great egret looks for breakfast at Calamvale Creek

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Scientific stuff

Bowl spider
Also known as
double-tailed tent spider,
Calamvale bowl spider

Species:
Cyrtophora exanthematica
Family: Araneidae — formerly Argiopidae

Size:
Body length. Female, 10-15 millimetres; male, 3 millimetres

Identification:
Colours of this species vary considerably. The larger female Calamvale bowl spiders are mostly light brown and match the colour of dead leaves. The spider has two blunt projections at the end of its abdomen.

Bowl spiders get their name from their unusual web, which is shaped like a bowl about 15-18 centimetres (6-7 inches) in diameter. The bowl also has a lid made of web.

The spider mixes green leaves at the end of a thin branch with dried out leaves irregularly placed around the web bowl, and sometimes replenishes them or moves house as they dry out or drop off the web.

The small males may share the outer limits of the female's web, as may other small spiders.

Personality: Inventive.
Untidy when the web ages and debris accumulates in it.

Using our photos

Photos on this website are copyright. If you want to use any, email us at: creeklife@gmail.com

Bianca's photos

Bianca is unusually large for a bowl spider. She is about 14 millimetres long (two-thirds of an inch), compared with 10-12 mm body length for most female bowl spiders (less than half an inch).

The photographer watched her and other nearby bowl spiders for several weeks.

He commented:

“When I first noticed Bianca's web it was very neat and looked like a perfectly formed bowl.

bowl_spider_web_9 (8K)

“I was amazed by the ingenuity that had gone into designing this complex bowl-shaped web with a lid, reinforced with fresh and dead leaves.

“Even though she is large for this type of spider, I didn't notice Bianca at first because she blended so well with the colour and texture of the dead leaves in her web.

“When I spotted her, she was difficult to photograph because she kept moving when my camera got close, so I couldn't get a clear focus on her.

“I returned to her web at various times of day and evening because I could never predict whether she would be in a position that allowed me to photograph her.

“As the weeks passed, I noticed her web became more and more messy. Sometimes she was eating food in it, then an egg sac appeared, and then it looked like a massive mess of leaf and bark bits.

“She seemed to toss out some of the dried leaves, and new green leaves appeared around the web.

“Many of the tidy, well-formed webs I had noticed in December and January had changed shape by March. Some had gone, but most had collapsed in on themselves, even though egg sacs were sometimes still visible.

“Bowl spiders are among the most extraordinary spiders I have seen.”

Critters of Calamvale Creek

Bianca, the bowl spider

Also known as double-tailed tent spider, Calamvale bowl spider

Cyrtophora exanthematica

Cyrtophora_exanthematica_spider web (47K)Good morning. Isn't this a wonderful day to catch a fly!

I'm Bianca the bowl spider. I build my web in the shape of a bowl, and strengthen and camouflage it with leaves. I like to build my home on the ends of thin overhanging branches, and I use the leaves and twigs at the end of the branch to build into my web. Some bowl spiders construct a web more like an upside-down tent, because we are related to tent-web spiders. But most of us at Calamvale Creek build them like a bowl.

bowl_spider_7 (23K)

You can see from the photo above how well I blend in with my surroundings of variously coloured dry leaves, twigs, and bark bits.

Meaning of my name

Cyrtophora_exanthematica_spider1 (18K)My scientific species name is Cyrtophora exanthematica. The first part, cyrto, comes from a Greek word that means “curved”. The second part, phora, means “bearer”. So my name means “curve bearer”.

My species is also found in Singapore, India, Papua New Guinea, Indonesia, Myanmar, Japan, and possibly other warm countries. In Singapore I am known as a double-tailed tent spider, because of the two projections at the posterior end of my abdomen.

Am I dangerous?

Cyrtophora_exanthematica_spider3 (21K) I'm not an aggressive spider, so I am unlikely to bite you unless you try to pick me up. My bite may make you feel uncomfortable, but I'm really interested only in insects.

My web

I put a lot of planning into my web, because it's not easy building a bowl out of web strands and leaves.

Our webs at first look like a masterpiece of architecture, but they become untidy after a while as they pick up dirt and tree pieces that fall into them.

I chose to build my home about 160 centimetres (5 feet 4 inches) above the ground, at the end of an overhanging branch. Other bowl spiders build their homes a little higher or lower, and people occasionally walk into the lower webs or accidentally knock them, without realizing a spider is inside.

bowl_spider_8 (21K)

Camouflage

Cyrtophora_exanthematica_spider5 (14K) Many people don't notice our webs, because the silk is not obvious and the leaves look like they are part of the tree (which they are most of the time). I build with more green leaves occasionally to continue the camouflage.

The shady paperbark trees around Calamvale Creek are a perfect environment for me. In fact there are dozens of our webs around the creek, although you may never see us unless you know what to look for.

Cyrtophora_exanthematica_spider6 (29K)My egg sac

When I produce my white oval egg sac, I lie face down on it with my legs outstretched (see photo at right, taken at sunset). It's a good way to look after the kids while I wait for a meal to drop in.

Quite a number of bowl spiders have made their homes around Calamvale Creek. If you find one of us, there will be others not far away.

— Bianca the bowl spider