This study investigates the effects of pederin, a hemolymph toxin that is accumulated in the eggs of most Paederus females, on potential arthropod predators of the offspring of P. fuscipes and P. riparius. Insects generally do not respond to pederin present in the prey. Paederus larvae are sufficiently agile to escape from these predators by running away, and the eggs are hidden by the females. Unlike insects, (wolf) spiders are deterred by prey with pederin. They turn away from larvae they have already captured and exhibit cleansing behavior. Larvae containing pederin survive the attacks of spiders without damage, whereas larvae descended from females that do not transfer pederin into their eggs are often killed and eaten. In the case of sudden attacks by spiders, the larvae have no chance of escape. Their survival thus depends on chemical defense. These investigations show for the first time why pederin might be of considerable importance for Paederus in the field.

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