Estimations of the predatory ability of spiders for young pine moth larvae

Abstract

Experiments were carried out to determine the predatory ability of spiders for 1st and 2nd instar larvae of the pine moth, Dendrolimus spectabilis BUTLER. HOLLING's (1959) ‘disc equation’ and WATT's (1959) equation were used in order to estimate abilities of spiders. The predatory ability of larger spiders, except the grass spider males, for 1st instar larvae was superior to that of smaller ones. Generally, spider males seem to be inferior to females and old nymphs as predators.The number of the 2nd instar larvae preyed upon by one spider decreased to about half of that in the case of the 1st instar larvae. It is concluded that the prey size is an important factor for the predation process.