Scavenging for dead prey

In a recent paper to the scientific journal Nature, Jamel Sandidge describes a surprising deviation from what is generally known about the feeding habits of spiders.

The brown recluse spider (Loxosceles reclusa) considered one of the most poisonous spiders, and found throughout Central North America, typically attacks the prey, injects venom and returns to the prey at its leisure in order to consume it. This behaviour is markedly different from other wandering spiders, which use vision, stealth and strength to subdue prey. Sandidge observed the brown recluse frequently attacking dead insects and retreating from live insects. He then set up a series of experiments in the laboratory and offered the spiders a choice between live and dead mealworm larvae, crickets and waxmoth larvae.

In 84 per cent of the trials, dead prey was preferred over live prey indicating a clear preference for scavenging over hunting.

If the brown recluse spider, considered as an opportunistic feeder, starts preferring dead prey over live prey, the number of insects available to it increases enormously.

Experimenting by feeding the brown recluse with Dead cockraoches poisoned by other spiders, cockroaches killed by insecticides and cockraoches dead for long, Sandidge observed that consuming dead prey confers substantial advantages to the brown recluse spider, especially if either the stage of decomposition of the insect or the manner in which the insect died does not affect the spider.

By employing scavenging as a primary method of ingestion, the spider reduces the amount of energy invested in subduing the prey. Consequently, a large number of spiders can flourish in urban environments where dead prey are frequently encountered due to the use of insecticides.

(Published in the Deccan Herald)

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