Distribution and Seasonal and Diurnal Activity Patterns of Eutrombicula alfreddugesi (Acari: Trombiculidae) in a Forest Edge Ecosystem

Abstract

Microclimatic and vegetative effects on the population size and activity patterns of larval Eutrombicula alfreddugesi Oudemans, 1910 (Acari: Trombiculidae), were investigated in Nebraska between latitude 40 degrees 0'0" N and 40 degrees 1'21" N. Larval population densities along a forest edge were greatest in areas of high relative humidity, moderate temperature, low incident sunlight, and increasing substrate vegetation. Although chigger populations existed throughout the forest edge, larger populations concentrated in short- to tall-grass transition zones. Chiggers were rarely found in the undergrowth beneath the tree canopy. Chigger activity correlated with a microclimatically driven diurnal rhythm. Activity was greatest during the late afternoon-early evening, between 1530 and 1930 hours (CDST). Larval activity dropped to low levels and remained so until sunrise; this period of reduced activity occurred between 1930 and 0530 hours. Small increases in larval activity occurred around sunrise (approximately 0600-0700 hours). Between about 0700 and 1530 hours, larval E. alfreddugesi were inactive and did not respond to normal sampling stimuli. Larval populations appeared in late April through early May, peaked in abundance in late June and early July, diminished through late summer, and disappeared in midautumn as the ground began to freeze.

Patterns of infestation by the trombiculid miteEutrombicula alfreddugesiin four sympatric lizard species (genusTropidurus) in northeastern Brazil

“…The species with the lowest infestation intensity was T. semitaeniatus, an exclusively saxicolous form. The types of habitat used by the lizards may influence the levels of infestation by mites, since the free stages of those parasites live buried in the soil (Clopton & Gold, 1993). Thus, lizards that live mostly in contact to the ground would theorically be prone to higher levels of infestation (Cunha-Barros & Rocha, 1995).…”

Patterns of parasitism by Eutrombicula alfreddugesi (Oudemans) (Acari, Trombiculidae) in three species of Tropidurus Wied (Squamata, Tropiduridae) from Cerrado habitat of Central Brazil

“…The lowest prevalence was recorded in lizards from urban and periurban areas of Brasília; this may be related to decrease in parasite densities in degraded areas. Indeed, as described by CLOPTON & GOLD (1993), populations of Eutrombicula alfreddugesi are susceptible to environmental variations, presenting density changes through a gradient of varying degrees of degradation.…”

Chiggers Recently Infesting Spea Spp. In Texas, Usa, Were Eutrombicula Alfreddugesi, Not Hannemania Sp.

“…Furthermore, the infested Spea spp. hosts were found in June and July (Torrence et al, 2007), the time of year when Spea toads typically are most active after heavy rains, and coinciding with the typical June-August peak activity period for E. alfreddugesi larvae (Loomis, 1956;Clopton and Gold, 1993). North American Hannemania spp.…”

“…As usually understood, E. alfreddugesi occurs as the most commonly encountered chigger throughout most of the eastern two-thirds of North America, including southern Canada, south through Mexico and Central America, into northern South America, and on some Caribbean islands (Jenkins, 1949;Loomis, 1956;Hoffmann, 1990). Furthermore, these mites successfully occupy an unusually wide array of habitats within their range (Jenkins, 1948;Loomis, 1956;Wrenn and Loomis, 1984;Clopton and Gold, 1993;Zippel et al, 1996). The documented host list for E. alfreddugesi is longer than that for any other chigger, .200 species of mammals, birds, reptiles, and amphibians (Jenkins, 1948(Jenkins, , 1949Wharton and Fuller, 1952;Wolfenbarger, 1952;Loomis, 1956;Hoffmann, 1990).…”