I was surprised to find this missing from the 6.xi.2015 "Challenge" puzzle (now closed).
Bolas. An essential tool for any gaucho.
There are even several species of spider that uses this technique to snare prey - the Bolas Spiders, of which there are 64 species spread across three Genera. These spiders are specialist hunters of moths, which can escape from a conventional web, courtesy of the fact that the wing scales stick to the web, but become detached from the wing, allowing the moths to escape. One of the best documented species is
Mastophora hutchinsoni from North America. A related species from Peru,
Mastophora dizzydeani, was named after a baseball player. Australians living along the Queensland coast can look out for
Ordgarius magnificus, which adopts an almost identical strategy to that of
Mastophora hutchinsoni, a nice example of convergent evolution in action. These spiders produce mimetic scents, mimicking the pheromones of female moths of target species, with which they lure the male moths into striking range, then swing their bolas web threads to snare and entangle the moth in mid-air.
You can watch one of these spiders in action via this YouTube video -
Bolas Spider in action.
I'm a little surprised that this word is missing from the word list. I'd hardly characterise it as esoteric.