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Abstract

Millipedes are known to have a variety of physical and chemical defenses to deter predators. Some species of tropical millipedes have considerably reduced primary defenses when compared to other tropical millipedes, but do retain chemical defense mechanisms. This study uses the tarantula Megaphobema mesomelas to test the effectiveness of a secondary defense mechanism, cyanide and benzaldehyde, from a species lacking a robust primary defense. Five tarantulas were found and collected around Monteverde, Costa Rica and brought into the Monteverde Biological Station. They were housed in tanks to allow for controlled feeding trials. Two treatment groups were created: millipedes with cyanide (c-millipedes) and without cyanide (n-millipedes). Each night for 12 nights tarantulas were randomly assigned a treatment and fed a millipede from their corresponding treatment group. It was recorded whether or not the tarantula ate the millipede. It was found that tarantulas had no preference for millipedes with or without cyanide. Tarantulas pounced and began to inject venom into millipedes in less than one second, whereas it took millipedes almost 12 seconds to release cyanide. It appears as though M. mesomelas are able to attack faster than the millipedes were able to release cyanide and thus are not exposed to cyanide. For this reason, the millipedes’ chemical defense mechanism was not effective in deterring M. mesomelas.

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