James T. Vogt

Flight energetics and dispersal capability of the fire ant, Solenopsis invicta Buren.

Experiments were conducted to estimate the flight capabilities of fire ant (Solenopsis invicta Buren) alates. These experiments were designed to: (1) quantify energetic expenditure during fixed flight; (2) characterize metabolic substrates of male and female alates; (3) estimate flight speed of male and female alates; and (4) quantify wingbeat frequency and water loss of females during flight. Flying males (in closed-system respirometry) increased metabolic rate approximately 38.4-fold over resting rate. Females increased metabolic rate approximately 51-fold (closed-system respirometry) and 48-fold (flow-through respirometry) over resting rate. Female alates had a mean respiratory quotient (RQ) of 0.999, indicating reliance on carbohydrates. The mean RQ of males was significantly lower (0.867). The flight speed of females on a circular flight mill averaged approximately 0.7 m s(-1), and increased with temperature but decreased with increasing body mass. The flight speed of males was 43% greater (approximately 1.0 m s(-1)) and increased linearly with temperature and increasing body mass. Female alates lost an average of 1.8 mg water h(-1) during flight. A simple energetics model, combined with previous work on the nutrient content of S. invicta and patterns of CO(2) release observed in this study, indicate that the flight capability of S. invicta female alates is limited to <5 km in the absence of wind.

Effects of temperature and season on foraging activity of red imported fire ants (Hymenoptera: Formicidae) in Oklahoma

Abstract Temperature and seasonal effects on foraging activity of Solenopsis invicta Buren (red imported fire ant) in Oklahoma were investigated by periodically quantifying the number of ants captured in baited vials for 2 yr. All temperature parameters (soil surface, 2 cm, 15 cm, mound surface, mound 5 cm deep, and mound 10 cm deep) except ambient at 1 m above soil surface were significant predictors of foraging activity; soil temperature at 15 cm was the best individual predictor, explaining 34% of variability in foraging activity. A combined quadratic model including mound surface temperature and season (weeks) explained 63% of the variability in foraging activity. Comparison with a similar study conducted in Florida revealed differences in the percentage of the year favorable for maximal foraging (≈25% in Oklahoma versus 42–59% in Florida). These data suggest that recommendations for timing of insecticidal bait applications against S. invicta that are appropriate in more southern portions of the fire ant range may not be appropriate for Oklahoma.

Prey of the Red Imported Fire Ant (Hymenoptera: Formicidae) in Oklahoma Peanuts

Abstract The red imported fire ant, Solenopsis invicta Buren, is an important predator in some cropping systems in the United States, particularly sugarcane and cotton, where it preys on key pests such as the sugarcane borer, Diatraea saccharalis (F.), and beet armyworm, Spodoptera exigua (Hübner). A study was undertaken to characterize the prey items collected by foraging S. invicta in an Oklahoma peanut field. From June to September 1999, 19 h of collecting yielded 1,276 foraged items. The largest percentage of foraged items (>20%) (other than unidentifiable fragments [39%]) were lepidopteran larvae, of which 87% were Stegasta bosqueella Chambers, the rednecked peanutworm. Overall, S. invicta collected approximately seven times more pest arthropods than beneficial arthropods. Forager success rates were ≈3.8 times higher for solids than liquids. Refuse piles in the field contained a large percentage of Coleoptera (≈26%) and did not mirror foraged material collections. Percent damaged pods on plants growing within S. invicta mounds was significantly (approximately three times) lower than on plants not within mounds. Additional data are presented on forager success rates and foraging/temperature relations.

Dietary Habits of Solenopsis invicta (Hymenoptera: Formicidae) in Four Oklahoma Habitats

Abstract Dietary habits of the red imported fire ant, Solenopsis invicta Buren, were investigated in four southern Oklahoma habitats: lakeshore, mixed grassland, wooded roadside, and unimproved pasture. Vegetation characteristics of each site were recorded for spring and late summer, in conjunction with estimates of forager success (the percentage of foragers returning to colonies with solid particles or liquid loads). Foragers collected a wide variety of solid particles, with different arthropod prey dominating samples within different sites. At the lakeshore site (no vegetation), dipteran adults, larvae, and pupae comprised >58% of foraged particles. Isoptera comprised >21% of foraged particles at the wooded roadsite site. At grassland and pasture sites, seeds (17.2 and 15.7%, respectively) were important foraged items. Forager success rates were highest for solids at the lakeshore site (≈30% and 16% in spring and late summer, respectively), and highest for liquids at the pasture site (≈30% and 22% for spring and late summer, respectively). Possible influence of vegetation on success rates, and implications for estimates of foraging energetics, are discussed.

Three-Dimensional Sampling Method for Characterizing Ant Mounds

Abstract A field-portable 3D laser scanner was employed as a means of digitizing the surface of fire ant (Solenopsis invicta Buren) mounds for analysis of shape and orientation in Mississippi and Oklahoma. Estimates of above-ground mound volume obtained through manual measurements of mound length, width, and height were higher and more variable than estimates obtained by summing the area underneath interpolated mound surfaces. Mounds were typically elliptical in shape and oriented in a north-south direction. The mound apex was offset to the northeast of the mean mound center by an average of 46 ± 5 mm. Additional mound characteristics extracted from 3D data included slope (degrees), surface area, and slope within mound aspect (northeast, southeast, etc.). Advantages of the methodology employed in this study and possible explanations for fire ant mound shape are discussed.

Temporal Foraging Activity of Selected Ant Species in Northern Mississippi During Summer Months1

A study was conducted in northeastern Mississippi to examine temporal foraging activity of imported fire ants (Solenopsis spp.) and other common ant species that inhabit pasture and meadow. Baited vials were placed horizontally on the ground along straight-line transects (n = 21) every 3 h for 24 h periods during June–August. Vials remained on the ground for 30 min, then were quickly plugged with cotton and collected. Principal species captured in baited vials included Solenopsis spp. (black and hybrid imported fire ant) (90.6%), Solenopsis molesta (Say) (5.9%), Monomorium minumum (Buckley) (2.5%), Tapinoma sessile (Say) (0.7%), and Paratrechina vividula (Nylander) (0.3%). Imported fire ants foraged during all time periods, as did S. molesta and P. vividula. Tapinoma sessile and M. minimum slowed or ceased foraging at night. Forelius pruinosus (Roger) was captured on a single date while sampling at 1800 h. Implications for timing of bait applications against imported fire ants are discussed.

Distribution and Size of Imported Fire Ant (Hymenoptera: Formicidae) Mounds in Recently Invaded Ball-and-Burlap Nurseries in Tennessee

A study was undertaken to describe size and distribution of imported fire ant mounds in south-central Tennessee ball-and-burlap plant nurseries to (1) improve survey and control measures and (2) assess the feasibility of airborne remote sensing for mound detection. Mounds were most numerous along roadsides and road cuts. Mounds in planted areas were larger than mounds along roadsides and road cuts, and mounds in open, grassy areas were of intermediate size (mean above-ground volume = 8.14, 4.36 and 5.32 L, respectively). An examination of mound size distribution in nursery landscapes indicated colony age-structure may not be consistent between landscape-date combinations, and mean mound size was smaller in July 2004 than in October 2003.

Imported fire ant (Hymenoptera: Formicidae) bioturbation and its influences on soils and turfgrass in a sod production agroecosystem.

Nutrient availability in ant-affected and undisturbed (control) soils, and in turfgrass in a sod production agroecosystem during the late summer were studied in the North Central Hills physiographic region of Mississippi, USA. Twenty plots were established in a bermudagrass (Cynodon dactylon × Cynodon transvaalensis cv. Tifway 419) tract. Paired soil samples were collected in September 2006 from active ant mounds and control sites. Turfgrass samples were collected from ant mound perimeters and adjacent undisturbed plots. C/N ratio, and Zn2+, total C, organic matter and total N contents were higher in disturbed soils than in the control soils. The mean mound pH was 6.0 (vs. 5.0 for the undisturbed microhabitats). The average P, K+, Ca2+ and Mg2+ contents were higher in imported fire ant (Solenopsis invicta) nest soil than in the control soil. Turfgrass harvested from ant mound perimeters had higher N, P, Ca2+ and S concentrations than that from the control soil. Cu2+ and Fe2+ were higher for ant-affected turfgrass. Elevated N levels and C/N ratios were detected in the ant nest soils. P, Ca2+, S, Cu2+ and Fe2+ contents between mould and control microhabitats did not significantly vary.