o. F. Francke-, J. C. Cokendolpher, Ann H. Horton, S. A. Phillips, Jr., and L. R. Potts

Transcription

1 VOL. 8 NO. 1 THE SOUTHWESTERN ENTOMOLOGIST MARCH 1983 f DISTRIBUTION OF FIREANTS!/IN TEXASl I 31 o. F. Francke, J. C. Cokendolpher, Ann H. Horton, S. A. Phillips, Jr., and L. R. Potts Texas Tech University, Lubbock, Tx ABSTRACT We surveyed 67 of 25 counties in Texas for the presence of fire ants during the spring and summer of The desert fire ant, Solenopsis ~ Wheeler, was found in three counties, two of which are records. Solenopsis ~ has now been reported from 0 counties in the state. The tropical fire ant, Solen ~~ geminata (Fabricius), was found in 28 counties, seven of which are records. Solenopsis geminata has now been reported from 78 counties in Texas. The red imported fire ant, Solenopsis invicta Buren, was found in 36 counties, including two records. This introduced species has now been reported from 110 counties in the state. The southern fire ant, Solenopsis xyloni McCook, was found in 3 counties. This species occurs in 131 counties 'in the state, including 19 records from this survey. RESUMEN Exploramos 67 de los 25 condados en Texas para determinar la presencia de las hormigas 'lavapies' 0 'tiracalzas', durante la primavera y verano de La hormiga lavapies del desierto, Solenopsis ~ Wheeler, fue hallada en tres condados, incluyendo dos nuevos hallazgos. Dicha hormiga ha sido ahora reportada en 0 condados. Encontramos a la hormiga lavapies tropical, Solenopsis geminata (Fabricius), en 28 condados, siete de los cuales representan nuevos hallazgos Solenopsis geminata ha sido ahora reportada en 78 condados del estado de Texas. La hormiga lavapies roja importada, Solenopsis invicta Buren, estuvo presente en 36 condados explorados. Esta especie ha sidoahora reportada en 110 condados de Texas, incluyendo dos nuevos descubrimientos. Finalmente, lahormiga lavapies sure~a, Solenopsis xyloni McCook, la encontramos en 3 condados, de los cuales 19 representan nuevos hallazgos. A esta especie ahora se Ie conoce en 131 condados del estado de Texas. INTRODUCTION,Four species of fire ants occur in Texas. The desert fire ant, Solenopsis aurea Wheeler, occurs in the w~stern regions, and the tropical fire ant, Solenopsis geminata (Fabricius), occurs in the southeastern regions. The southern II Hymenoptera: Formicidae llcontribution No. TlO15. College of Agricultural Sciences, Texas Tech University, Lubbock, Tx. Supported by Interagency Agreement, No , Texas Department of Agriculture. lldepartment of Biological Sciences. Texas Tech University. All other authors, Department of Entomology, 32

2 fire ant, Solenopsis xyloni McCook, occurs throughout Texas. The red imported fire ant, Solenopsis invicta Buren, has spread throughout the eastern onehalf of the state, and presumably continues to spread westward. Solenopsis invicta is considered both an urban and an agricultural pest primarily because of its mounds (often used to identify it), and because of the symptoms experienced by those stung. However,~. geminata and~. xyloni also construct mounds under certain conditions, and the symptoms resulting from their stings are often very similar to those produced by S. invicta. Thus, when fire ants interact with humans the blame is often directed at the imported fire ant even though in reality the culprit is one of the native species. Identification of the various species is a tedious and difficult task. Errors are often made, and those misidentifications affect our perception of the seriousness of S. invicta as a pest, of its increasing or decreasing rate of spread, and of its current distribution. Furthermore, the similarities of the red imported fire ant to native fire ants have potentially important consequences regarding the enforcement of intra and interstate quarantine regulations. Since 1978, several surveys of fire ants have been made in Texas in various regions of the state (Francke and Merickel 1981, Moody and Francke 1982, Moody et al. 1981, Neece and Bartell 1982, Wangberg et al. 1980). Over 8500 ant samples collected during these surveys have been placed in the insect collection at Texas Tech University. About 1000 of these samples include fire ant species. During the spring and summer of 1982 we surveyed for fire ants in 67 counties, primarily along the western limits of distribution of S. invicta. Thirty county records of fire ants were obtained. The objective of this report is to update the known distribution of fire ants in Texas. MATERIALS AND METHODS We surveyed primarily in open areas, such as highway medians and intersections, roadside parks, pastures, etc., which are the preferred habitat of S. invicta. Consecutive localities were seldom more than 50 km apart, and a ~ariable amount of time (seldom over one h) was spent at each locality. In addition to turning over any rocks or logs of suitable size, we searched the area for evidence of ant excavation activities (mounds, craters, etc.), and suspicious looking dirt mounds were poked with a shovel. If any ants were found under objects or appeared on the disturbed surface, they were identified to genus at the collection site, and if they were fire ants an adequate sample was gathered with an aspirator. The samples were subsequently transferred to containers filled with 80% ethyl alcohol and labelled according to standard taxonomic procedures. The ants were identified using the taxonomic keys of Wojcik et al. (1976) and Hung et al. (1977). RESULTS The survey included 175 localities, 11 of which were located at the border between two counties (in which case any fire ant species was recorded as occurring in both counties). The localities were in 67 different counties (Table 1), with a minimum of one, a maximum of 10, and an average of 2.6 localities/county surveyed. Of collections made at the 11 county junctions, two had none, five had species that had been already reported for both counties, two had a species that had not been recorded in one of the counties~. geminata at BrooksHidalgo line, and S. invicta at FreestoneNavarro line), and two' had species that were records for both counties (~. xyloni at BurnetWilliamson line a~d KarnesWilson line). No fire ants were found in eight counties; however, in seven of these only one locality was sampled. A single species of fire ant was found in 26 counties: six with~. geminata, nine with~. invicta, and 11 with ~~ xyloni. Two species were found in 2 counties: nine counties had~. geminata and~. invicta, four counties had~. geminata and~. xyloni, and 11 counties had~. invicta and~. xyloni. Eight counties ccntained three species of fire ants within their boundaries: in two counties... aurea,... geminata and... xyloni were pre 33

3 Table 1. The Distribution of Fire Ants (Genus llolenopsis) in Texas~1 County!. ~!. geminata!. invicta!. xyloni Anderson,5 Andrews Angelina Aransas 2,3 * Archer Armstrong Atascosa 2,3,,5 Austin 2 Bailey Bandera,5 Bastrop 1,3 Baylor Bee 3,,5,5 2,3, Bell,5 Bexar 2,3, Blanco 2,3,,5,5 Borden Bosque Bowie 3, Brazoria 2,3, Brazos 2,3, 2,3, Brewster Brisco Brooks Brown 3, Burleson 2,3, Burnet *. Caldwell Calhoun 3, Callahan Cameron 2,3, Camp Carson Cass Castro *,5,5 Chambers Cherokee Childress Clay Cochran Coke Coleman Collin Collingsworth Colorado Coma1 Comanche Concho Cooke Coryell Cottle Crane Crockett Crosby 2,3,,5 2,3,,5. Culberson 2, 3

4 County S. aurea ~. geminata S. invicta ~. xyloni Dallam Dallas 2:~ 3,,5 2,3, Dawson Deaf Smith Delta Denton DeWitt Dickens 3,,5,5,5 Dinunitt Donley Duval Eastland Ector Edwards Ellis ElPaso Erath Falls Fannin Fayette Fisher Floyd Foard Fort Bend Franklin Freestone Frio Gaines Galveston Garza Gillespie Glasscock Goliad Gonzales Gray Grayson Gregg Grimes Guadalupe Hale Hall Hamilton Hansford Hardeman Hardin Harris Harrison Hartley Haskell Hays Hemphill Henderson Hidalgo Hill Hockley 2,3, 2,3, 2,3, 2,3,,5 2,3, 2,3,,5 3,,5 2,3, 3, 2,3,,5 2,3, 2,3,,5,5 1 2,3,5,5,5,5,5,5 2,3,,5 1,3 2,3, 2,3, 3 2,3, 2,3,,5 2,3, 2,3,,5 2,3, 2,3,,5 2,3, 2,3, 2,3, 2,3, * 2,3,,5 35

5 County ~. ~ ~. geminata S. invicta... xyloni Hood Hopkins Houston Howard Hudspeth Hunt Hutchinson Irion Jack Jackson Jasper Jeff Davis Jefferson Jim Hogg Jim Wells Johnson Jones Karnes Kaufman Kendall Kenedy Kent Kerr Kimble King Kinney K1eberg Knox Lamar Lamb Lampasas La Salle Lavaca Lee Leon Liberty Limestone Lipscomb Live Oak Llano Loving Lubbock Lyqn Madison Marion Martin Mason Matagorda Maverick McCulloch McLennan McMullen Medina Menard Midland Milam 2,3,,5 2,3, 2,3 2,3, 2,3,,5 3,,5 2,3,,5 2,3,,5,5 2,3,,5 2,3, 2,3, 2,3, 2,3, 3, 3, 2,3,,5 3,,5 2,3, 2,3, 2,3, 2,3,,5 1,3,5,5,5 *,5,5,5,5 3 2,3, 2,3,,5 2,3, 2,3,,5 2,3, 3, 3,,5 36

6 County.. ~,,_. geminata,,_ invicta E. xyloni Mills Mitchell Montague Montgomery Moore Morris Motley Naco$doches Navarro Newton Nolan Nueces Ochiltree Oldham Orange Palo Pinto Panola Parker Parmer Pecos Polk Potter Pre~idio Rains Randall Reagan Real Red River Reeves Refugio Roberts Robertson Rockwall Runnels Rusk Sabine San Augustine San Jacinto San Patricio San Saba Schleicher Scurry Shackelford Shelby Sherman Smith Somervell Starr Stephens Sterling Stoall Sutton Swisher Tarrant Taylor Terrell 3, 3, 2,3, 2,3, 2,3, 2,3, 2,3, 2,3, 2,3, 1,3 * 2,3, 2,3,,5 2,3, 2,.), 2,3,,5 2,3,,5 2,3, 2,3, * 2,3,,5 2,3, 2,3, 1,3,5 3,,5 2,3, 2, 2,3, 2,3, 37

7 County ~. aurea ~. geminata ~. invicta ~. xyloni Terry Throckmorton Titus Tom Green Travis Trinity Tyler Upshu,r Upton Uvalde Val Verde Van Zandt Victoria Walker Waller Ward 2,3, 2,3, 2,3,,5 2,3, 2,3, 2,3, 3, 1,3 *,5,5 *,5 2,3,,5 2,3, 2,3,,5 2,3, Washington 2,3, 2,3, Webb Wharton 3, '3, Wheeler Wichita 2,3, Wi1barger Willacy Williamson,5 Wilson 3,,5,5 Winkler Wise Wood Yoakum *,5 Young Zapata Zavala,5 2,3,,5 ~/ Compiled from (1) Summerlin and Green 1977, (2) Hung et a , (3) Hung and Vinson 1989, () Moody et ale 1980, (5) Present study, (*) Texas Agricultural Extension Service/Texas Department of Agriculture 1982 Records (Mr. Mark Trostle, Personal Communication). = Counties surveyed during present study. serit, and in six counties we found ~. geminata, E... invicta and~. xy1oni. In only one county were all four species of ants found. Overall we obtained 30 county records, distributed as follows: two for ~. aurea, seven for ~. geminata, two for ~. invicta, and 19 for ~. xy1oni. The known distribution, by county, of the four species of fire ants found in Texas is given in Table 1 ( county records are clearly identified) and in Figs. 1. The current distribution of fire ants in Texas can be summarized as follows: no fire ants have been reported from 52 of the 25 counties in the state, 86 counties reportedly have one species of fire ant, 79 counties have two species, 32 counties have three species, and only four counties harbor all four of the species found in the state. 38

8 Solenopsis ~ has been reported fro~ 0 counties, occurring by itself in eight, with~. xylon! in 21, with both~. geminata and ~. invicta in one, with both~. geminata and ~. xyloni in five, with both ~ invicta and ~. xyloni in one, and with the three other species in four counties. Solenopsis geminata has been reported from 78 counties; it occurs by itself in twelve, with~. invicta in 26, with~. xyloni in four, with both ~. ~ and ~. invicta in one, with both~. aurea and ~. xyloni in five, with both~. invicta and~. xyloni in 26, and together with the three other species in four counties.. Solenopsis invicta has been reported from 110 counties; it occurs alone in 2, with~. geminata in 26, with~. xyloni in 28, with both ~. ~ and ~. geminata in one,: with both ~. ~ and ~. xyloni in one, with both ~. geminata and~. xyloni in 26, and with the three native spe.cies of fire ants in four counties. Finally, ~. xyloni has been reported from 131 counties: it is found alone in 2 counties, with ~. ~ in 21, with~. geminata in four, with~. invicta in 28, with both ~. ~ and~. geminata in five, with both ~. ~ and~. invicta in one, with both~. geminata and~. invicta in 26, and with the three other species in four counties. DISCUSSION Solenopsis invicta and~. geminata are broadly sympatric, and both species are largely allopatric with ~.~. Solenopsis aurea is a relatively rare, goldenyellow ant easily separated from the other three species on the basis of color. Solenopsis geminata is characterized by major workers with disproportionately large heads that simplify identification. However, in the absence of such major workers, the separation of ~. geminata from~. invicta is rather difficult. Because the distribution of~. geminata coincides with that of ~. invicta over most of their present range in Texas, however, there is little risk that an identification error between these two species would alter our percep~ tion of their ranges, and of the rate and direction of spread of S. invicta. Solenopsis xyloni is found throughout the state, and its range overlaps' those of the three other species. As previously indicated, the goldenyellow color of S. aurea simplifies the task of recognizing it. The separation of S. xyloni fr~m~. geminata is simple if major workers of the latter are present~ and is rather difficult j f. only minor or medium workers are present in the sample. The separation of~. invicta from~. xyloni is the most difficult one among the permutations possible with the four species. Samples consisting of only a few minor workers are virtually impossible to separate and identify consistently. Thus, we foresee potential complications with regulation and control efforts, because ~. xyloni is widespread in areas of the state that are not currently infested by S. invicta. A misidentified sample from an area well beyond the present 'contin~ous' range of S. invicta could indeed affect our perception of the range of the species, and of its rate and direction of spread. ACKNOWLEDGEMENT We would like to thank Drs. Donald Ashdown, James K. Wangberg, and Jeff Whitworth for their comments on the manuscript. Ms. Lorie A. Prien and MS. Mary Peek are also gratefully acknowledged for processing the various drafts of the typescript. Thanks are also extended to Mr. Mark Trostle for providing the Texas Department of Agriculture 1981 and 1982 records. 39

9 FIGS. 1. The distribution of fire ants in Texas. 1. Solenopsis aurea Wheeler. 2. ~. geminata (Fabricius). 3. ~. invicta Buren,. ~. xyloni McCook 0

10 LITERATURE CITED Francke, O. F., and F. W. Mericke Two species of Pogonomyrmex ~harvester ants from Texas (Hymenoptera: Formicidae). PanPac. Entomo1. 57:3719. Hung, A. C. F., M. R. Bar1in, and S. B. Vinson Identification, distribution, and biology of fire ants in Texas. Tex. Agric. Exp.Stn., Misc. Pub. B1185, 2 pp. Hung, A. C. F., and S. B. Vinson Factors affecting the distribution of fire ants in Texas (Myrmicinae: Formicidae). Southwest. Nat. 23:2051. Moody, J. V., and Q. F. Francke The Ants (Hymneoptera: Formicidae) of Western Texas. Part 1. Subfamily Myrmicinae. Grad. Studies, Texas Tech Univ., No. 27, 80 pp. Moody, J. V., O. F. Francke, and F. W. Mericke The distribution of fire ants, Solenopsis (Solenopsis) in Western Texas (Hymenoptera: Formicidae). J. Kans. Entomo1. Soc. 5:6980. Neece, K. C., and D. P. Bartell A Faunistic Survey of the Organisms Associated with Ants of Western Texas. Grad. Studies~ Texas Tech Univ., No. 25, 36 pp. Summerlin, J.W., and L. R. Green Red imported fire ant: A review on invasion, distribution, and control in Texas. Southwest. Entomo1. 2: Wangberg, J. K., J. D. Ewig, Jr., and C. K. Pinson The relationship of Solenopsis invicta Buren to soils of East Texas. Southwest Entomo1. 5: Wojcik, D.P.,W. F. Buren, E. E. Grisse11, and T. Car1ys1e The fire ants (Solenopsis) of Florida (Hymenoptera: Formicidae). Fla. Dep. Agric. Consum. Serv., D~y. 'Plant Ind., Entomo1. Circ. No. 173, pp. 1