Comprehensive Description

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Comprehensive Description

Rather than constructing an orb web like many of its close relatives, adult female Mastophora bolas spiders construct a "bolas" (named after a traditional South American throwing weapon)-- a sticky globule at the end of a silk thread --and hold it with a foreleg. This behavior was first reported by C.E. Hutchinson in 1903, based on observations in southern California (Yeargan 1994). Spiders hunt with a bolas only at night. The female releases an allomonal blend that mimics the chemical signals used in long-range mate attraction by her moth prey (an allomone is a chemical produced by an organism which induces in a member of another species a behavioral or physiological reaction favorable to the emitter). Because female moths are the mimicked signalers in this system, only male moths (duped responders) are subject to predation by the spider. Based on their studies of Mastophora hutchinsoni in Kentucky, Haynes et al. (2001) suggest that there is a dynamic interplay between olfactory cues (pheromone mimics) emitted by the bolas spider and mechanosensory cues (wing vibrations) from the moth, which are detected by the spider. The bolas spider aggressively mimics the pheromone blend of its moth prey. Spiders frequently emit this chemical cue even before they have produced the weapon (bolas) that would allow them to capture a moth. The allomone attracts prey moths that are downwind of the spider. The wing vibrations of an approaching moth stimulate the spider to produce a bolas. Subsequently, wing vibrations also stimulate the strike that allows the spider to capture its prey. (Haynes et al. 2001).

Eberhard (1977, 1980) studying a previously undescribed species of Mastophora in Colombia, was the first to confirm the suspicion of the early naturalists that Mastophora lures its prey with a volatile substance that mimics the sex attractant pheromone of virgin female moths. In formally describing this species (Eberhard 1980), he named it Mastophora dizzydeanii, explaining: "Since this spider’s livelihood depends on throwing a ball fast and accurately, it seems appropriate to name it in honor of one of the greatest baseball pitchers of all time, Jerome "Dizzy" Dean."

Bolas spiders, a group including five recognized genera, are known from most parts of the world outside temperate Eurasia, but about half of the known species of Mastophora occur in South America (Yeargan 1994 and references therein).


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© Shapiro, Leo

Source: EOL Rapid Response Team


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