An 'in Situ' Coring Technique for Estimating the Population Size of House Dust Mites in Their Natural Habitat

An in situ core sampling method was used to obtain absolute population density estimates for the mite, Dermatophagoides pteronyssinus Trouessart (Acari : Pyroglyphidae) in the mattress habitat. At the 95 % fiducial limit the numbers of D. pteronyssinus in the top 1.5 cm of substrata were 8,200-26,800 mites m• Mite densities that were calculated from vacuum samples of the same habitat underestimated the abundance of D. pteronyssinus by more than three orders of magnitude. Vacuuming did not detect all mite species inhabiting the mattress, and eggs and immature mites were under-represented in vacuum samples. The importance of absolute population estimates versus relative estimates of abundance and population density indices is discussed, and a number of ways in which the core sampling approach may contribute to future house dust mite research are suggested. RESUME : Resume : Vne methode de preJevement par carottage, « in situ », de Dermatophagoides pteronyssinus Trouessart (Acari : Pyroglyphidae) du matelas est utili see pour estimer la densite absolue de population de l'acarien. A la limite fiducielle de 95 %, le nombre de D. pteronyssinus dans les 1,5 cm superieurs du substrat etait de 8.200-26.800 acariens/m • Les densites d'acariens calculees a partir de prelevements par aspirateur sur le meme habitat sous-estimaient l'abondance de D. pteronyssinus de plus de trois ordres de magnitude. L'aspirateur ne recoltait toutes les especes d'acariens vivant dans le matelas, et les reufs et les immatures etaient sous representes dans ces echantillons. L'importance des estimations de densite absolue de population par rapport aux estimations relatives des indices d'abondance et de densite de population, est discutee, et il est sugere comment une telle approche de prelevement a la source peut contribuer dans l'avenir a la recherche sur les acariens de la poussiere des maisons. INTRODUCTION aI., 1990). House dust mites have been a major focus for research since they were first implicated in allergic disease in the mid 1960s (VOORHORST et al., 1964; OSHIMA, 1964), but our grasp of the ecology of these mites has been painstakingly slow to develop in the last three decades (COLLOFF, 1991a). Ironically, the bio-medical emphasis of the research has often obscured progress in house dust ecology; most studies have been biassed towards clinical issues (e.g. the quantification of allergens), and The dust that collects in the human domestic environment provides a habitat for xerophilic fungi and a number of pyroglyphid mites (Acari : Pyroglyphidae) loosely termed" the house dust mites ". These mites include members of the genera Dermatophagoides and Euroglyphus that are a cause of asthma, rhinitis and atopic dermatitis in a large proportion of allergic patients (reviewed by FAIN et * Department of Zoology, University of Oxford, South Parks Road, Oxford, OXI 3PS, UK. Present address : Department of Educational Studies, University of Surrey, Guildford, Surrey, GU2 5XH, UK. Acarologia, t. XXXVI, fase. 4, 1995.