Macroparasites are parasites that are large enough to be seen with the naked eye, in contrast to microparasites. They grow in one host but reproduce by infective stages outside this host. These generally include ticks, mites, helminths (nematodes, flatworms, etc.), and can be either external parasites (ectoparasitic) or internal parasites (endoparasitic). The most abundant macroparasite in humans is the nematode Ascaris lumbricoides which causes an infection called ascariasis. Macroparasites are also parasitic of many plant species and can be a significant agricultural pest.