• UNIVERSITY MICROFILMS, ANN ARBOR, MICH. $ LC Card no. Mic 58-1479• WALLWORK, John Anthony. THE ACARINA OF A HEMLOCK YELLOW BIRCH FOREST FLOOR. University of MichiganPh. D., 1957Zoology00) T) 1) d bl) DD Ü 0) THE ACARINA OF A HEÎÛLOCK-YELLOW BIRCHFOREST FLOORbyJohn A. WallworkA dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the University of Michigan1957Doctoral Committee: Professor Samuel A. Graham, Chalman Assistant Professor Irving J. Cantrail Professor Theodore H. Hubbell Professor Stephen H. SpurrTHE ACARINA OF A HEM LOCK-YELLOW BIRCH FOREST FLOOR. byJohn A. Wallwork. ABSTRACTThis study investigated population fluctuations, vertical and horizontal distribution, and feeding habits of the mites of a Hemlock-Yellow Birch forest floor, at Imp Lake, Michigan.-Special attention was paid to the role of these animals in the selective decomposition of litter material, and the interaction between the mites and other components of the forest soil eco-system. A modification of the Berlese technique for the extraction of small arthropods was used. Soil samples, 2 sq. cms, in area, and of volume 15 ccs. were subjected to this technique, and the data checking the efficiency of this method showed that for most of the mite species considered, between 85% and 100% of the population was recovered at the end of 36 to 40 hours. Other procedures included measuring temperature and moisture fluctuations within the soil profile, copper-constantin thermocouples and fiberglas units being used, In culturing mites in the laboratory, the plaster of Paris block method developed by Edwards (1955) was most satisfactory. 12The mites were the most abundant mesofaunal element in this locality, their numbers far exceeded those of the Collembola, pseudoscorpions, spiders, and nemat odea.'Variations in the nature and structure of thesoil profile influenced the distribution of mites. With regard to temperature and moisture fluctuations, behaviour under experimental conditions was correlated with the distribution of field populations, fost species showed a low tolerance to dry conditions, but moisture only acted as a limiting factor in the upper portions on the litter. The two principle temperature responses were (1) an avoiding reaction and,(2) a conditioning response, which was difficult to distinguish from heat torpor in many cases. Both vertical and horizontal distribution of the mites were influenced by food habit. Aggregations formed during summer and winter were largely due to localisations around food supply. Temperature changes were more effective in winter, when some movement of'individuals from litter to humus was a response to unfavourable temperature conditions in the litter. Extremes of temperature acted as limiting factors for population size. The population fluctuations and age class distribution through the year were Influenced by temperature conditions, although this effect was offset in several cases by the migratory powers of the mites. 3Factors producing mortality included the predatory activities of other mites, pseudoscorpions, spiders, and insect larvae; fungal infections; fungal capture; high temperatures and low moisture conditions. Four groups of soil mites were represented in collections; Orlbatel, Mesostigmata, Trombidifomes, and Acaridiae. 74 genera were present, of which 45 belonged to the Orlbatel, 14 to the Mesostigmata, 13 to the Trombidifomes, and 2 to the Acaridiae. The dominant species was Oppia neerlandica, frequently occurring species included Pelorlbates sp.. Scheloribates pallidulus, Brachychthonlus lapponlcus …