Some web-building spiders can form memories of the prey they catch, and the rare the ability has now been documented in black widows, who can retain information about their prey鈥檚 size and the location where it was ensnared in the spider鈥檚 web.
After 鈥檚 previous research revealed that , he and his colleagues were eager to see if the black-and-red arachnids could form memories of their meals.
Sergi, who was at the University of Wisconsin at the time of the work, and his team collected 69 female wild western black widow spiders (Latrodectus hesperus) in Oregon and allowed each of them to build webs in enclosures in the lab. They then dropped crickets 鈥� a tasty treat for a black widow 鈥� onto some of the webs.
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鈥淲e let the spiders interact with the cricket, wrap them up in silk, and then begin their trip back to their retreat where they go to rest and eat,鈥� says Sergi. 鈥淩ight when they started walking back, we鈥檇 steal the cricket from them.鈥� Other spiders were allowed to enjoy their meal undisturbed.
The spiders that had their prey snatched began searching around their enclosure for the lost meal immediately or within seconds. They spent between 30 seconds and 22 minutes, with an average of 10 minutes, searching for their lost prey. 鈥淏asically all the spiders that we stole crickets from searched, and all the spiders that we didn鈥檛 [steal from] didn鈥檛 search,鈥� says Sergi.
Spiders that received the biggest, juiciest crickets looked a few minutes longer, on average, than those who had smaller meals pilfered 鈥� but only if those crickets were tangled in the vertical part of the web that reaches the ground, called the gumfooted lines. In the wild, gumfooted lines capture ground-dwelling grubs such as ants and beetles that make up most of the spiders鈥� diet.
If the prey was trapped in the horizontal canopy-like web, the spiders were less inclined to search for the lost meal. Large crickets caught in gumfooted lines elicited longer search time than smaller crickets, but when prey was snagged in the canopy, spiders showed less interest overall. That suggests that black widows can recall details of the size of their prey and where it was caught in their web.
The finding that black widows are more responsive to crickets thieved from the ground may be because flying prey is rarer and 鈥渆cologically and evolutionarily less important than catching terrestrial prey鈥�, says Sergi.
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