Parasite, Giant Rot Grub

If a creature with this special attack hits with the indicated attack (usually a claw or bite attack), it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity. The creature has the option to conduct the grapple normally, or simply to use the part of its body it used in the grab to hold the opponent. If it chooses to do the latter, it takes a –20 penalty on its combat maneuver check to make and maintain the grapple, but does not gain the grappled condition itself. A successful hold does not deal any extra damage unless the creature also has the constrict special attack. If the creature does not constrict, each successful grapple check it makes during successive rounds automatically deals the damage indicated for the attack that established the hold. Otherwise, it deals constriction damage as well (the amount is given in the creature's descriptive text). Creatures with grab receive a +4 bonus on combat maneuver checks made to start and maintain a grapple. Unless otherwise noted, grab works only against opponents no larger than the same size category as the creature. If the creature can use grab on sizes other than the default, this is noted in the creature's Special Attacks line.

A creature with this ability can poison those it attacks. The effects of the poison, including its save, frequency, and cure, are included in the creature's description. The saving throw to resist a poison is usually a Fort save (DC 10 + 1/2 the poisoning creature's racial HD + the creature's Con modifier; the exact DC is given in the creature's descriptive text). Poisons can be removed through neutralize poison and similar effects.

A rot grub that is grappling a foe and chooses to damage the foe with an additional grapple check deals twice its normal bite damage (2d6+6 for most giant rot grubs), in addition to injecting an additional dose of poison with each successful check.