n. a species that depends on another for survival but generally does not kill it. There are many intestinal parasites that are of value in the digestion of food for their hosts. Some parasites induce illness or debilitation but do not weaken the host so severely that it (and therefore the parasite) will die. Others will survive only if they can find an alternative host before the death of their current host; some of these parasites can alter the behavior of their hosts to make transfer to another host more likely. —parasiticadj.