Distribution and dispersal of the chigger Neotrombicula autumnalis (Shaw, 1790) (Trombiculidae, Acari). Part I. The behaviour of the unfed and feeding larva

In summer hatched larvae move upwards from the soil to the lower part of the vegetation. On sharp edges of litter particles or pieces of vegetation the larvae meet to form clusters. In case no contact with a host occurs these clusters are immobile for at least several weeks. The clusters react on heat rays with questing behaviour of the legs and with some locomotory activity of the individual mites, without any distinct movement to or from the heat source. Only after direct contact of an active host with the immobile cluster, the larvae assume a parasitic mode of life. They walk over the outer surface of fur or feathers, presumably to the first part of naked skin encountered. They cluster again and penetrate the epidermis with their dnathosoma to start feeding. The harvest mite does not seem to have any preference for host species within the mammal or bird taxa. The mobility of the potential host in the litter layer of the soil rather than the activity of the unfed larvae determines success and level of parasitism, and governs the dispersal of the mites.