Effect of bombardier beetle spray on a wolf spider: repellency and leg autotomy

Summary. Data are presented on the repellency of the spray of a bombardier beetle (Pheropsophus aequinoctialis) to a lycosid spider (Lycosa ceratiola). The secretion is shown to cause the spider to desist from its assault on the beetle within, on average, 58 ms of onset of the beetle’s secretory emission, a reaction time that is at a par with latencies previously reported for startle, escape, and avoidance reactions of cockroaches, flies, and moths. Spray ejections by the beetle, are shorter in duration (43 ms, on average) than the response time of the spider, an indication that the beetle does indeed pack a formidable “punch” into its ejection. After being hit by a beetle’s spray, L. ceratiola were found occasionally to autotomize one or two of their legs. It is argued, but not proven, that this unusually severe effect from exposure to an arthropodan defensive secretion may be caused by the high temperature of the bombardier beetle spray.