ONTOGENIC CHANGE IN SURVIVAL VALUE OF LEG AUTOTOMY IN A WOLF SPIDER, GLADICOSA-PULCHRA (KEYSERLING) (ARANEAE, LYCOSIDAE), DURING SCORPION ATTACKS

The survival value of leg autotomy during attacks by scorpions (Vaejovis waueri Gertsch and Soleglad, 1972 (Scorpiones: Vaejovidae)) was assessed in three successive instars of the wolf spider Gladicosa pulchra (Keyserling, 1877) (Araneae: Lycosidae). During the first three instars after hatching, spiders were subjected to predatory encounters with adult scorpions. Spider survival due to leg autotomy decreased and the tendency of scorpions to use the sting to subdue the spiders increased with increasing size of wolf spider instars. As spider instar size increased, more scorpion attacks were directed at the cephalothorax and abdomen, resulting in decreased opportunity for larger spiders to utilize leg autotomy as an escape tactic. The decrease in survival and change in scorpion predatory tactics with increasing instar size reflect an increase in the relative body size of the spiders. Therefore, the survival value of an antipredator mechanism may vary with the degree of opportunity to use the mechanism.