72 ENTOMOLOGICALNEWS DESTRUCTION OF YOUNG COLONIES OF THE RED IMPORTED FIRE ANT BY THE PAVEMENT ANT (HYMENOPTERA: FORMICIDAE)1 Thomas G. King, ShermanA. Phillips,Jr.2 ABSTRACT:Therangesoftheredimportedfireant.So/enops/s/nvicta,andthepavement ant, Tetramoriumcaespitum. arenowvirtuallycontiguous in NorthCarolina,and these species haveundoubtedly interacted.OurlaboratorystudyshowsthatT. caespitum will destroy young S. invicta colonies placed within its foraging range. If5. invicta moves northward, interactionsbetween thesetwospeciesmay intensify. Thepavementant,Tetramoriumcaespitum (L.),andthered imported fire ant, Solenopsis invicta Buren, can both rapidly mobilize many workerstodominatelargefoodsources.Oftenthisattempttodominatea resourceresultsinconflictwithotherantspecieswhichtheyeliminateor "extirpate" as the situation requires (Wilson, 1971). Interspecific con- flicts between ant species resulting in numerous deaths rarelyoccur in temperate ecosystems (see MacKay and MacKay 1982 for exceptions), but can occur when more than one extirpating species cohabit in an ecosystem. These conflicts occurred when S. invicta. a native ofSouth America,wasintroducedintoAlabamainthe 1940's(HungandVinson, 1978).IthassincespreadacrossmostofthesouthernU.S.A.,eliminating the native, dominant species from much of their former range. At present, territorial limits of S. invicta in North America are largely defined by abiotic factors, namely cold weather in its northernmost range and arid conditions in its westernmost range(Hungand Vinson, 1978). Bhatkar et al. (1972) suggested that the northward expansion ofS. invictamayhavebeenslowedorhaltedbythepresenceofLasiusneoniger Emery, an aggressive and populous northern ant species. They stated that L. neoniger colonies, although numbering less than 1000 ants, maintained between 8,000 and 10,000 nests per acre in two study areas. Thisdensity,coupledwiththedistinctlysuperiorcombativecapabilities demonstrated against S. invicta. may allow this ant to successfully compete with S. invicta. Ifso, L. neoniger could be ont ofthe agents of DeceivedOctober 1, 1991. Accepted March 10, 1992. ^Department of Agronomy, Horticulture and Entomology, Texas Tech University, Lubbock.Texas 79409. ENT. NEWS 103(3): 72-77. May&June, 1992 Vol. 103,No. 3,May&June, 1992 73 indigenousbiologicalcontrol restrictingthe rangeofS. invicta in North America. T.caespitumoccursthroughoutmuchoftheHolarcticandEthiopian faunal realms and has been reported on every continent except Antarctica(Creighton, 1950).Inmuchofitsextensiverange,itmaintains a prominent role, often sharing that position with L. neoniger in the Nearctic, andL. niger(L.) andL. alienus Forsterin the Palearctic (Brian andElmes, 1974;Creighton, 1950).Presently,theNorthAmericanrange ofT. caespitum includestheAtlanticCoastsouthtoNorthCarolina,and sporadic and occasionally extensive regions west to California (Creighton, 1950;NuhnandWright, 1980).InthePalearctic,T.caespitum lives inopen areas,scavengingforinsects andcollectingseeds (Brianet al, 1967;Brown, 1957;Smith, 1943).IntheNearctic,thespeciesisusually confined to areas near human habitations (Brown, 1957; Creighton, 1950). ThepresentrangesofT. caespitum andS. invicta are nowcontiguous in North Carolina, and the assumption that somecontact has occurred betweenthesetwohighlysuccessfulspeciesisnotunreasonable.Contact shouldcontinuetooccurbecausethepotentiallynorthernmostrangeof S. invicta(PimmandBartell, 1980)overlapswiththesouthernmostrange ofT. caespitum (T.G.K., personal observation). The present laboratory studydescribes the reactionofT. caespitum to repeated introductionsof both young colonies and single foundress queens of5. invicta placed within its foraging range. Although the final results obtained from the interaction of T. caespitum and S. invicta are restricted to conditions imposed by a controlled environment, the actual responses observed resultingfromtheforcedinteractionsshouldsimulatenormalbehaviors ofT. caespitum to repeated incursions by S. invicta under more natural conditions. MATERIALS AND METHODS Acolonyofapproximately 15workersandonequeenofT.caespitum. collectedin latesummerof1988 from BucksCounty,Pennsylvania, was reared in an artificial nest placed within a four square meter, Fluon- coatedplasticenclosure.Theantswerefedinsectsandsugarwater(50% sucrose),supplied with a sourceoffreewater,and kept at a temperature of approximately 25C. After six months, the colony numbered more than 2,000 workers. Polygyne colonies (two or more queens percolony) of S. invicta from KerrCounty,Texas,werecollected in earlyspringof1989 anddivided intosixsub-colonies,each containingtwoqueens,between 100 and 200workers, and brood. Test tube nests were used to house the ENTOMOLOGICALNEWS 74 sub-colonies. All artificial nests wereconstructed accordingto Bankset al (1981).Oncedailyforthreedays,asub-colonywasplaced20cm from thematureT.caespitum nestwithinthefoursquaremeterenclosure,and the sequence and timingofthe sub-colony's destruction were recorded. Subsequently,thethreeothersub-colonieswereintroducedsequentially as previously described, but this time at one meter distances. Finally, three S. invicta queens were placed within the foraging area, and interspecific interactions were observed and recorded. RESULTS When theS. invicta sub-colonieswereplaced20cm from the T. caes- pitum nest, several S. invicta workers made contact with T. caespitum foragers within one minute. S. invicta attacked T. caespitum duringthis initial contact, grasping them with their mandibles and repeatedly stingingthe foreignworkers.Curiously,individual T. caespitum workers rarely engaged S. invicta workers unless supported by nestmates, often waiting foradditional workers to arrive before advancingtoward theS. invicta nest. These supporting T. caespitum workers arrived within 10 minutes. Isolated T. caespitum workers that became surrounded by S. invicta usuallyceased theirmovement and subsequently retreated to an area where T. caespitum formed a sizeable majority. Due to this tech- nique, T. caespitum approached the S. invicta nest as a mass of ap- proximately 100workersslowlymovingtowardthesourceofaggression. S. invictaworkersthatenteredthemassofapproachingT.caespitumwere capturedbysingleT. caespitumworkersthatgrabbedoneoftheS. invicta worker's appendages. Other T. caespitum workers then grabbed other appendages, pulling in opposite directions and causing the severingof theseizedappendages.TheT.caespitumworkerswouldalsosting,butthe sting appeared to have little effect on the S. invicta workers. Between five minutes and one-halfhour passed before T. caespitum had incapacitated all S. invicta workers in the foraging area and began enteringtheS. invicta nest.Whenencounteringthetesttubenest,T. caes- pitum workers lunged inward, attempting to grab the gasterflagging S. invictaworkersatthenestentrance.Gasterflagging,aprocessofspraying venom on enemies, caused T. caespitum to spasm for approxi- mately 10 seconds before returning to normal. Ifa T. caespitum worker succeeded in grabbing a 5. invicta worker, it would quickly withdraw, draggingtheS.invictaworkerintothemassofT.caespitumwhereitwould be dismembered. In this slow fashion, T. caespitum pulled S. invicta workers, one at a time, out of their nest to be killed by the mass of Vol. 103, No. 3, May&June. 1992 75 beleaguered T. caespitum. The T. caespitwn progression into the S. invicta nestcontinueduntilallS.invictaweredead.ThecapturedS. invictabrood were taken back to the T. caespitum nest, presumably to be eaten. When S. invicta nests were placed one meter from the T. caespitum colony, the sequence was the same but required more time. Contact between the species occurred within 2 minutes, and more than 10 T. caespitum workers gathered within 15 minutes to attack the S. invicta aggressors. More S1. invicta workers had time to leave the nest; and as a result,the T. caespitum workers took longerto encircle theS. invicta nest site. Also, the S. invicta colony was able to escape to a new location shortly after T. caespitum workers began penetrating its nest. This reaction prolonged theconflict,sinceapproximately 15 minutes passed beforeT.caespitumdiscoveredtheS. invictacolony'snewnestingsite.The rediscoveryoftheS. invicta colonyresulted in a second atack, following which 5. invicta scattered. Within one day, all S. invicta were killed. T. caespitum suffered less than two dozen fatalities per trial, with death resulting primarily due to numerous S. invicta stings. A single queen ofS. invicta was capable of killing a T. caespitum worker. Actual captureofS. invicta queens therefore required several T. caespitum workers acting together, pulling at the queen's appendages andstingingrepeatedly.NoneoftheS. invictaqueenswerecapturedafter 10 minutes, but all were killed within 24 hours. DISCUSSION TherangesofT.caespitum andS. invictaarenowcontiguousinNorth Carolina, and the two species have probablyencountered one another. This study shows that T. caespitum may have the potential ofdelaying expansion of S. invicta. In North American the success of T. caespitum has been limited primarily to human inhabited areas.These areas alreadyoccupy large portions ofthe Atlantic seaboard and continue to gain in size. T. caespitum is extremely territorial, a trait evidenced by frequent conspecificwars(Wilson, 1971;Brianetal., 1966).Asaresult,destruction of the young S. invicta colonies by T. caespitum was expected. Not expected was theefficiencyofattackby T. caespitum because more than five S. invicta workers died for every T. caespitum worker killed. The success of the T. caespitum attack depended on cooperation between workers and the ability to maintain a homogeneous mass ofattacking workers within which S. invicta workers would be dismembered. In England,theseskillfulattackmethodsenableT.caespitumto"rout"large ENTOMOLOGICALNEWS 76 colonies ofL alienus, and defeatcolonies ofL niger(Brian etal, 1966). Colonies of T. caespitum contain an average of approximately 10,000 workers(Brian, 1979);whereasmatureS. invictacoloniesmaintaininexcess of 60,000 workers (Tschinkel, 1986). Conflicts between mature colonies, therefore, could result in S. invicta overwhelming T. caespitum. Colder temperaturesretardcolonygrowthinlaboratorycoloniesofS.invicta (Porter, 1988); and as a result,theaveragecolonysizeof S. invicta and T. caespitum maybe morecomparable in the northernmost rangeofS. invicta. Ifnot, T. caespitum may dominate its habitat only if it destroys young S. invicta colonies in the field as it did in the laboratory. Ourstudysimplyidentifiesonepotentialbioticfactorwhichmayimpose mortality on S. invicta. However, the results we obtained (destruction ofS. invicta) are limited to conditions inherent in laboratory studies ofthis type. Therefore, although the responses ofT. caespitum toS. invicta are accurate, caution should be exercised regarding the T effectiveness of caespitum as a controlling agent until field studies are conducted to substantiate ourlaboratory findings. ACKNOWLEDGMENTS WethankAP.Bhatkar,M.V.Brian,J.C.Cokendolpher,M.L.Peek,andH.G.Thorvilson for their critical reviews. This manuscript is contribution T-4-286, College ofAgricultural Sciences,TexasTechUniversity. LITERATURECITED Banks, W.A., C.S. Lofgren, D.P. Jouvenaz, C.E. Stringer, P.M. Bishop, D.F. Williams,D.P.Wojcik,andB.M.Glancey. 1981. Techniquesforcollecting,rearing and handling imported fire ants. U.S.D.A. Science and Education Administration, Adv.Agric.Tech.,South.Sen,No.21,9p. Bhatkar, A.P., W.H. Whitcomb, W.F. Buren, P. Callahan, and T. Carlysle. 1972. ConfrontationbehaviorbetweenLasiusneonigerand the imported fire ant. Environ. Entomol. 1:274-279. Brian, M.V. 1979. Habitatdifferences in sexual production by two coexistent ants. J. AnimalEcol.48:943-953. Brian,M.V.,J.Hibble,andA.F.Kelly. 1966. Thedispersionofantspeciesinasouthern English heath.J.Animal Ecol.35:281-290. Brian, M.V.,G.W. Elmes,andA.F. Kelly. 1967. Populations oftheant Tetramorium caespitum Latrielle.J.Animal Ecol. 35:281-290. Brian,M.V.and G.W. Elmes. 1974. Productionsoftheant Tetramoriumcaespitum in thesouthern Englishheath.J.Animal Ecol.43:889-903. Brown, W. 1957. Is the ant genus Tetramorium native in North America? Breviora. 72:1-4. Creighton,W.S. 1950. TheantsofNorthAmerica.Bull.Mus.Comp.Zool.HarvardUniv. 104:1-585. Hung,A.C.F. and S.B.Vinson. 1978. Factors affectingthedistributionoffireants in Texas. Southwest.Nat.23(2):205-214. Vol. 103,No. 3,May&June, 1992 77 MacKay, W. and E. MacKay. 1982. Coexistence and competitive displacement involvingtwo nativeantspecies. SouthwestNat. 27:135-142. Nuhn, T.P. and C.G. Wright. 1980. An ecological sup'ey ofants in a landscaped suburban habitat.Am. Mid.Nat. 102(2):353-362. Pimm,S.C.andD.P.Bartell. 1980. Statisticalmodelforpredictingtherangeexpansion ofthe red imported fireant.Ann. Entomol. Soc. Am. 73:261. Porter, S.D. 1988. Impactoftemperatureoncolonygrowthanddevelopmental ratesof theant,Solenopsisinvicta. J. Insect Physiol. 34:1127-1133. Smith,M.R. 1943.AntsinthegenusTetramoriumintheUnitedStateswithadescriptionof a new species. Proc. Entomol. Soc.Wash.45:1-5. Tschinkel, W.R. 1986. The ecological nature ofthe fire ant: some aspects ofcolony functionandsomeunansweredquestions,pp.72-87.in Fireantsand Leafcutterants: biology and management.Westview. Boulder,Colorado.435 pp. Wilson, E.O. 1971. TheInsectSocieties. Belknap. Cambridge, Massachusetts. 548 pp. CALVERT AWARDS FOR 1991 AND 1992 In 1987 the American Entomological Society initiated the Calvert Award to be pre- sentedannuallytoayoungpersoninthegreaterDelawareValleyforanoutstandinginsect- related project.TheAward was named in honorofDr. Philip P.Calvertwhojoined the Societyasateenager,laterbecameitspresident,andwasamemberfor74years.Asapro- fessorofbiology at the UniversityofPennsylvania and an associate ofthe Academy of NaturalSciencesofPhiladelphia,Dr.Calvertplayedanimportantroleinstimulatingan interest in insectsamongyoungpeople. ThisyeartheCalvertAwardwaspresentedtoAmyDorfman,atenthgradestudentat CentralHighSchoolin Philadelphia thesameschoolfromwhichCalvertgraduatedin 1888!Herprojectwasentitled,"Farnesolvs.NaturalPredation:WilltheBenefitsofaLar- vacide Outweigh the Advantages of Interaction in a Food Chain?" President Joseph Sheldon presented Miss Dorfman with one-year memberships in the American Ento- mological Society and the Young Entomologists' Society, a one-year subscription to EntomologicalNews, andacheckfor$50.Amy'sprojectandthoseofthreeotherstudents attheDelawareValleyScience FairsweredisplayedattheApril22membershipmeeting at theAcademyofNatural Sciences. First runner-up was Dawn Riddle, a ninth grade student also from Central High School,whoseprojectwason,"TheEffectsofChemicalsonthePheromoneTrailsofAnts." Two honorable mentions were awarded, both to juniors from Ocean Township High School,Oakhurst,NewJersey.Gisela Insvastestudiedthe"EffectofProtozoanLambor- nellaclarkion Larval Populations ofthe MosquitoAedesaegypti in the Laboratory"and DenisShmulermadea"ComparisonofStemandLeafGrowthofEuropeanVioletsGer- minated in HarvesterAntNests." LastyearAmy Dorfman'sprojectwas firstrunner-uptothatofHelenGlezos,thena sophomoreatWoodstownHighSchool,Woodstown,NewJersey,whoaddressedtheques- tion,"DoesCaptiveFeedingIncreasetheGrowthandLifeSpanofthePrayingMantis?" Second runner-up in 1991 was presented to Kevin Bonner, a ninth grade student at ArchbishopWood High School,Warminster, Pennsylvania. Hestudied"Substance Pre- ferenceamongCarpenterAnts."TheawardswerepresentedonApril24ataSocietymeet- ing featuring Dr. Thomas Donnelly, a particularly appropriate guest speaker. Dr. Donnelly had met Philip P. Calvert through their mutual interest in dragonflies. At the beginningofhis talk he related someofhis memoriesofDr. Calvert. Harold B. White