Author
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Morrison, Lloyd |
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Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/12/2003 Publication Date: 10/15/2004 Citation: Morrison, L.W. 2004. Spatiotemporal Variation in Antlion (Neuroptera: Myrmeleontidae) Density and Impacts on Ant and Generalized Arthropod Foraging. Annals of the Entomological Society of America. 97(5): 913-922. Interpretive Summary: Research on potential biological control agents for exotic insect species in the U.S., such as the imported fire ant, Solenopsis invicta, is designed to find and enhance natural predators, parasites, and disease agents. These often come from the native range of the pest, but existing predators in the U.S. may also have an impact. Antlion larvae are predators of ants and other arthropods, constructing funnel-shaped pits to capture prey. Under certain conditions, however, the distribution and abundance of antlion pits may increase, resulting in an overall greater impact of predation on ants and other arthropods. A scientist working at the University of Texas and now with the USDA-ARS, Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, has found that the distribution and abundance of antlions may increase dramatically in response to extended dry weather, increasing the risk of predation to ants and other arthropods. The foraging activity of fire ants was much lower i areas with high antlion densities. Additionally, during periods when antlion densities were similar, ants foraged less in sheltered areas (where antlions were a permanent feature of the community) than in exposed areas (where antlion abundances varied over time due to climatic variation). Our understanding of the community structure and function of arthropods, particularly the effect of predators on ant foraging behavior, might aid in the design of biological control programs for pests such as the fire ant. Technical Abstract: Antlion larvae that construct conical pits to capture prey may strongly affect ant foraging behavior, but are usually restricted to sheltered microhabitats. Under certain conditions, however, the distribution and abundance of pit-building antlion larvae may increase resulting in a greater predation risk for foraging ants and other arthropods. An increase ein larval antlion (Myrmeleon crudelis) densities in exposed areas occurred in central Texas in the late summer and early fall of 1998, presumably because of extended dry conditions. Isolated rainfall events decreased pit densities, sometimes to zero, but pit densities returned to high levels as the soil dried out. Pit densities in exposed areas declined in October 1998 and remained low until August 1999, presumably because of more rainfall during this period. Pit densities in sheltered areas remained relatively constant over the entire year (August 1998 - August 1999). Pitfall traps at sheltered sites indicated that ants and other arthropods foraged significantly less inside antlion zones than in adjacent areas without antlions. At exposed sites, ants foraged significantly less when antlion pits were present (dry conditions) than when they were absent (wet conditions); there was no significant difference in foraging outside the antlion zones in wet vs. dry conditions. Ants also foraged significantly less inside antlion zones at sheltered sites (which were permanent) vs. exposed sites (which were transient), which were characterized by similar pit densities. Attraction of ants to baits revealed similar patterns. Temporal variation in antlion larval distribution and abundance may result in a substantially increased predation risk to ants and other arthropods. |
