Polyethism in foraging in a polymorphic predator, Enoplognatha ovata (Araneae : Theridiidae): A case for balance

Two colour morphs of Enoplognatha ovata (Clerck), "redimita" and "lineata," the abdomens of which are whitish with two pink stripes and greyish-yellow , respectively, differ in their foraging strategies. When placed in artific ial arenas with flowering stems to ascend, we noted that both morphs had a strong tendency to wander over the ground rather than ascend a stem [unlike the crab spider, Misumena vatia Clerck (Araneae: Thomisidae)], but that li neata was significantly more prone to wander than was redimita. Neither mor ph showed choice for the type of stem or colour of flower. Nevertheless, re dimita showed a greater preference for choosing white artificial flowers (d iscs) atop 30-cm wooden rods than did lineata. We propose that the relative abundances of the two colour morphs in the natural population represents a balanced polymorphism which is maintained in part by polyethism in hunting strategies, with redimita being more fastidious in its selection of crypti c hunting sites in flowers than is lineata, and the latter being more crypt ic and more errant on the ground.