Alan B. Cady

Modular Habitat Refugia Enhance Generalist Predators and Lower Plant Damage in Soybeans

Abstract Promoting generalist predators in agriculture via habitat manipulation has gained much interest in biocontrol research. Straw shelters have been used by Chinese farmers for >2,000 yr to provide temporary spider refugia during cyclic farming disturbances. This method, however, has not been systematically investigated on larger scales in western-style agriculture. Our preliminary observations indicated a significant decrease in the abundance of spiders (76%) and their egg sacs (75%), after conventional tillage of soybeans [Glycine max (L.) Merr.]. We hypothesized that providing alternative habitats in tilled fields could conserve predatory assemblages following this major disturbance. We used modular habitat refugia constructed of chicken wire loosely filled with bedding straw to provide temporary habitats for epigeic predators in a soybean field. Refugia held 5–36 times the spider density compared with open field, and the production of spider egg sacs was enhanced 18–87 times. Almost 60% more spider species were found in refugia than in open field. Abundance of harvestmen, carabids, and staphylinid beetles also significantly increased in habitat refugia. Increased habitat cover and provision of alternative prey in habitat refugia may have caused this dramatic predator increase. Soybean seedlings grown within 1 m of habitat refugia suffered 33% less insect damage compared with plants at control locations. Decrease in seedling damage, however, did not significantly increase soybean seed production. Applications of discrete habitat refugia may provide an alternative to habitat manipulation techniques to conserve and augment arthropod predators in agroecosystems.

Diet Composition and Significance of Earthworms as Food of Harvestmen (Arachnida: Opiliones)

Abstract We gathered dietary data for several harvestman species in a soybean field and adjacent hedgerow habitats to assess the extent of their polyphagy. A total of 1032 harvestmen, predominantly Leiobunum spp., were observed during almost 50 search hours over two seasons. More harvestmen and increased foraging activity were observed in the hedgerow than in the soybean field, and in both habitats harvestmen were more active at night. Earthworms (Oligochaeta: Lumbricidae) were the prey items most frequently recorded as being consumed by all observed harvestman species in both habitats (47.1%), while fruit and other plant material constituted 18.1% of the records. Feeding trials conducted with female harvestmen, Hadrobunus maculosus (Wood), revealed that these arachnids were not capable of subduing live earthworms, suggesting that consumption of these in the field might be limited to scavenging. Implications of harvestman foraging for local food web dynamics are discussed.

Distribution and importance of spiders inhabiting a Brazilian sugar cane plantation

The spider fauna (Araneae) of a sugar eane plantation was surveyed monthly by hand colteetion and beating vegetation in sugar cane fields across Botucatu, State of Sao Paulo, Brazil. Composition and rchness (family and species where identifieation to species was possible) microhabitat preferenees were reeorded, and diversity and evenness indices were calculated. A total of 1291 spiders belonging to 73 species and 20 families were collected. The most diverse families were Theridiidae, Salticidae, and Araneidae, and the most abundant ones were Theridiidae, Saltieidae, Anyphaenidae, and Araneidae, Seven species represented 58.6% of the total fauna, with Crysso pulcherrima (Mello-Leitao,1917) (Theridiidae) composing 28.2%. About 65% of the spiders occupied the upper part of the plants (above 20 cm). Five spider species were present in the sugar cane throughout crop development. Evidence of spiders feeding on sugar cane pest species was observed.