I witnessed a curious interaction today. A 7 spot ladybird was walking up a wall, when a sudden movement caught my eye. It was a large spider, a female Amaurobius similis that had dashed out of her burrow in a hole in the wall, probably alerted by the pull of one of the silk threads that radiate from her burrow. She had caught the ladybird by one leg. The ladybird struggled to free itself, but she need not fight much. After a few moments, the spider released her grip, turned round and retreated into her burrow. The spider obviously had assessed the ladybird and regarded it not suitable for a meal. I doubt it was due to the ladybird size or strength, as Amaurobius are powerful spiders, able to subdue large flying insects such as droneflies and honeybees. The other possibility is that the spider has tasted the alkaloid rich liquid that constitutes ladybirds chemical defence mechanism and that is released from their leg joints when alarmed (the 'blood reflex'). I have previously seen dead ladybirds wrapped on silk caught on the webs of two spider species (garden spiders Araneus diadematus and the false widow Steatoda bipunctata). Indeed, field surveys and experiments carried out by John Sloggett showed that A. diadematus does trap and consume ladybirds, and is apparently immune to the toxic effects of ladybird's chemical defences. In contrast, other spider species do seem to find ladybirds distasteful, so this is a strong possibility for Amaurobius.
Another view of the interaction, not as sharp, but it shows clearly how the spider's chelicerae are pulling and lifting the ladybird's front right leg.
For other spiders, however, ladybirds are not even considered a food item. Take this little wolf spider, enjoying the company of the 7 spot ladybird a few days ago. Both individuals were sunbathing next to each other most of the morning. The spider popped in and out, paying no attention whatsoever to the ladybird.
More information
Sloggett, J. (2010). Predation of ladybird beetles by the orb-web spider Araneus diadematus BioControl, 55 (5), 631-638 DOI: 10.1007/s10526-010-9291-0
Fascinating! I've sometimes seen ladybirds caught in webs and wrapped up in silk and have wondered whether the spider actually ate them e.g. http://cabinetofcuriosities-greenfingers.blogspot.co.uk/2010/09/embarrassment-of-riches.html
ReplyDeleteThank you Rob, great macro shots in your post too.
ReplyDeletePerhaps the ladybird's 'shell' is just too tough?
ReplyDeleteBut this raised another question in my mind: do spiders find anything distasteful, i.e. does a spider have a sense of taste?
This one may well have sensed and reacted to the ladybird's secretions but is that 'tasting?'
How interesting! Especially as I also sat today and observed a ladybird 'playing tag' with a wolf spider.Then a female wolf spider(much much larger) appeared and straddled the ladybird briefly. There was no sign of aggression that I could see during this interaction, I just wish I knew what it all meant.
ReplyDeletecheers.