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No. 80: Mar-Apr 1992

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Spider Swordplay

Ventral view of D. raptor spider
Ventral view of D. raptor. The claws are on the tips of the bottom two pairs of legs. Greatly enlarged photos reveal them to be wicked-looking fang-like structures.
D. raptor, a Hawaiian spider, has lost its ability to spin webs and therewith capture prey. This unusual spider, however, has evolved:

"...one of the most remarkable morphological features ever found in spiders (immense elongations of the tarsal claws)."

These claws, just visible on the two lowermost pairs of legs in the sketch, are employed to skewer passing insects in flight:

"The spider is strictly nocturnal, spending most of the activity-period hanging upside down from silk threads. Small insects are snagged directly from the air using a single long claw. For larger insects the spider uses both long claws on legs I, or sometimes all the long claws."

(Gillespie, Rosemary G.; "Impaled Prey," Nature, 355:212, 1992.)

Comment. Nature has produced many remarkable creatures. They become anomalous only if they cannot be explained as the products of small, random, cumulative mutations.

From Science Frontiers #80, MAR-APR 1992. � 1992-2000 William R. Corliss