}
    // Trapdoor spiders only hide themsleves under the floor when they
    // can't see their prey.
    if (type == MONS_TRAPDOOR_SPIDER)
    {
        const actor* _foe = get_foe();
        return (_foe == NULL || !can_see(_foe));

    // Trapdoor spiders only unsubmerge when their foe is in sight if
    // the foe is right next to them.
    if (mon->type == MONS_TRAPDOOR_SPIDER)
    {
        const actor* foe = mon->get_foe();
        if (foe != NULL && mon->can_see(foe)
            && !adjacent(mon->pos(), foe->pos()))
        {
            return (false);
        }
    }