The Population Composition of a Spider Community in West Central Missouri

Abstract

Two hundred and two species of spiders representing 22 families were found in the spider population of a two-acre plot typical of west central Missouri. An average population of 51 spiders per m2 showed that 15 species were numerical dominants having an incidence of .25 to 5.4 individuals per M2. Several species were found to have preferential habitats in the three stratified communities sampled. The total population reached a peak in July and remained rather uniform through September. Primary and secondary peaks of the adult popu- lation occurred in May and September, respectively. The dominant species varied widely in their constancy and density of occurrence in the communities. Population dynamics of Ceraticelus fissiceps (O P-Cam- bridge), Synema parvulum (Hentz), Tmarus angulatus (Walckenaer), Anyphaena fraterna (Banks), and Mangora placida (Hentz) offer evi- dence regarding life cycles and overwintering habits of these species. The two-acre plot upon which this study was conducted is near Warrensburg, Johnson Co., Missouri. A small stream transects the plot diagonally, and there are two prominent outcroppings of Warrensburg sandstone. Approximately one-fourth of the area is occupied by a house, driveway, and lawns. The small patches of lawn are interspersed among areas of shrubs, trees, and other vegetation largely in their natural state. Although fragments of prairie and exist in considerable variety, forest conditions predominate. The relief is about 25 feet between the lower, moist, swampy por- tions and the higher parts of the area, which drain quickly and dry rapidly and excessively. The soil, mainly Harrison silt loam, varies from swampy muck through hard clay to loose sand. Oak (Quercus spp.), sycamore (Platanus occidentalis), elm (Ulmus spp.), osage orange (Maclura pomifera), and willow (Salix spp.), are the pre- dominant trees. Buckbrush (Symphoricarpos sp.), blackberry (Rubus sp.), and sumac (Rhus spp.) are the principal shrubs. The herbaceous community is composed in large part of jewel weed (Impatiens sp.), beggar's lice (Desmodium sp.), ragweed (Ambrosia spp.), and various grasses and sedges (Poa spp., Hordeum sp., Carex sDp., and Panicum spp.). The plot encompasses habitats broadly typical of west- central Missouri. The spider populations studies of Gibson (1947) in the west Ten- nessee river forest, of Elliott (1930) in an Indiana beech-maple climax, and of Lowrie (1942 and 1948) are related geographically and ecologically to this study. Those of Muma and Muma (1949) in the Nebraska prairie, of Barnes (1953) and Barnes and Barnes (1955) in the eastern piedmont meadow habitat also afford a basis for comparison. Other spider population studies include those of