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    Terrifying spider species found to hunt in packs and co-ordinate attacks on prey

    A team of French researchers found these spiders take down their prey in packs using specialised web vibrations. (Picture: Credit Bernard Dupont / Wikimedia Commons)

    Like spiders weren’t already terrifying enough, researchers have observed one species capable of hunting in packs of hundreds.

    The Anelosimus eximius, a species of spider native to South America, can reportedly move ‘in unison’ and coordinate their attacks on prey, according to a new study.

    A team of French researchers found these spiders take down their prey in packs using specialised web vibrations.

    The spiders live in large towering non-stick webs and can suddenly swarm over insects that fall into them. They collectively do this using a two-pronged attack, moving as one and then staying still to perceive vibrations coming through the web. 

    The study was led by Raphaël Jeanson, a researcher at the French National Centre for Scientific Research, Paris (CNRS), and published in Proceedings of the National Academy of Sciences. 

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    The researchers used a dead fly connected to a vibration generator, brought into contact with a web, to trigger the collective spider hunting behaviour in French Guiana. 

    ‘When the prey falls in the web, this triggers the movement of the spiders,’ Jeanson told Live Science. 

    ‘But after a while, they all stop for a few milliseconds before they start moving again,’ he explained.

    Social spiders are notable for living together in large colonies, cooperating on prey capture, sharing parental duties and rarely straying from their basket-shaped nests.

    Among the 50,000 known species of spiders, about 20 have developed a permanent social life characterised by such social cooperation. 

    Among the social spiders, the eximius species may be one of only two that hunt ‘in packs’, helping them catch insects including moths and grasshoppers. 

    Their colonies can house several thousand individuals of all ages, co-existing peacefully in gigantic webs that often reach several cubic metres. 

    The researchers used a dead fly connected to a vibration generator, brought into contact with a web, to trigger the collective spider hunting behaviour (Picture: Bernard Dupont)

    ‘Nests are typically composed of a horizontal basket-shaped silken sheet and a network of vertical threads, connected to the vegetation, used to intercept flying prey,’ the authors say.

    ‘A massive and rapid accumulation of spiders on the prey is all the more important as the webs of A. eximius are not sticky and the risk is high of the prey escaping before being seized by spiders,’ they said. 

    It’s already know that the spiders of this species cooperate when capturing insects trapped on the web using coordinated movements. By combining fieldwork and modelling, the research team identified the actions involved in the synchronisation of these movements.  

    A. eximius spiders close in on prey in two stages depending on web vibrations – they close in on their struggling victim in unison, or, alternatively stand still as one, the team found. 

    ‘An individual’s decision to move depends on the relative intensity of vibrations emitted by the prey and the moving spiders,’ the team said in their paper.

    The spider is native to South America and creates sprawling webs to trap prey (Credits: Getty Images)

    ‘This rule allows the group to adapt quickly to any change in prey size or the number of spiders involved in the hunt,’ they said,

    Synchronisation involves a modulation of each spider’s behaviour, according to the relative intensity of the prey’s signals compared to those of the other spiders. Meaning, the spiders remain motionless on the web when vibrations emitted by fellow spiders are masking vibrations coming from prey. 

    ‘It’s a bit like when you are in a room with people chatting,’ said Jeanson. 

    This coordination increases the spiders’ ability to detect prey and optimises their hunting performance. In this way, they are able to capture prey up to several hundred times their size.  

    Interestingly, the more social spiders are, the smaller they tend to be so you’re unlikely to find gigantic spiders hunting in packs. 


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