Why do they get together like this? does this behaviour give them some advantage early in their lives?
Experiments revealed that spiderlings can survive and make normal webs when reared in isolation. Although communality does not seem necessary for survival, communally reared spiderlings survival rates were higher than spiderlings reared in isolation. High air humidities made spiderlings came closer together in their communal webs: this could be an adaptation to avoid becaming trapped in water dropplets in the rain when isolated which can easily result in drowning for such small animals. The communal behaviour could also offer protection against predators: all spiderlings sitting in the middle of a radial web is a very good sensory device that could provide them an early warning system for approaching predators, especially when coupled with their surprising explosive dispersal reaction to minimum disturbance.
When the air was dry and the yolk has been absorbed, spiderlings came apart from each other, and it is in such dry conditions that spiderlings make a long silk thread that allows them to balloon in the air and disperse from their natal place.
This is the cocoon spiderlings emerged from
Spiderling ball. The communal web is just visible
The spiderlings felt a little gust of air -from my breathing near them when taking the photo above - and rapidly came apart.
More information
Burch, T . L . 1979. The importance of communal experience to survival for spiderlings of Araneus diadematus (Araneae : Araneidae). J . Arachnol . 7 :1-18 . here.
8 comments:
Oh, now that is just way too cool! Great pics - great info. I've never seen a spider ball (yet), but I shall now keep my eyes peeled for them!
That is too cute... I've seen a few, and there's always this "Awwwww!" moment. I guess that means I'm a hopeless bug addict... ;-)
Your first picture is wonderful. I live in hope that I'll run across a spider-ball out there somewhere.
Thank you Ellen, Antje and Joy for your comments. Joy, I hope you see one soon, I think there is still hope this year!
This is a brilliant source of information and thank you for the references. I've never understood why they ball together.
My son loves these balls (despite hating bigger spiders) and he's doing this as a topic poster during his Covid-19 lockdown distance learning. We found one in the garden that has literally appeared overnight and has drawn a picture. Thanks for helping to inspire him, he's nearly 5.
Sammi - uk
Hi Sammi, happy you found the blog useful, especially great you are managing to support your son with it. You may want to consider submitting your spiderling ball findings to the British Arachnological Society spiderling survey here: http://britishspiders.org.uk/wiki2015/index.php?title=Main_Page
Thank you! I had a cluster of them on an object that didn't exist last autumn. You're the first source I've found that confirms that they make their own webs to live in rather than staying in the web from the cacoon. You solved a mystery for me.
I saw a spider ball for the first time a few days ago on a drain pipe in my back yard. I was sure it was just a piece of moss, but when I touched it to confirm, the tiny spiders shot off quickly in all directions. Never too old to learn something new! Perhaps nature intended them to look like a piece of moss as a disguise from predators?
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