COMPARISON OF THE FEEDING NICHE OF POLYPHAGOUS INSECTIVORES (ARANEAE)IN A TEXAS COTTON PLANTATION - ESTIMATES OF NICHE BREADTH AND OVERLAP

The feeding niches of 10 spider species that are polyphagous insectivo res were compared by computing coefficients of niche breadth and niche overlap. The study is based on predation evidence from an insecticide -free cotton plantation in east Texas. All overlap values were < 1.00 (range, 0.08-0.94), which indicates that each spider species has its o wn feeding niche in the cotton agroecosystem. Diet breadth, that is in versely related to feeding specialization, was computed for each speci es. The highest value was approximately five times higher than the min imum, which indicates considerable differences between species in feed ing specialization. Diet breadth values indicate that large web weaver s exhibited a less specialized feeding behaviour (relatively broad fee ding niche) compared with small web weavers (narrow feeding niche). Pr ey specialists in this study concentrated on either aphids or fire ant s as a primary food source. The nonweb-building spider Oxyopes salticu s Hentz, which actively searches the cotton plant for prey (up to almo st-equal-to 6 mm maximum length), showed the highest diet breadth valu e (broad feeding niche) under the conditions of this experiment. This abundant species, which is considered a highly beneficial biocontrol a gent of smaller cotton pests, shows high flexibility in its foraging p atterns.