Behavioral interactions of falcigera, Camponotus variegatus, Anoplolepis gracilipes, and Wasmannia auropunctata (: Formicidae) with the geographically co-occurring subterranean Coptotermes formosanus in Hawaii. Ranit Kirschenbaum and J. Kenneth Grace Department of Plant and Environmental Protection Sciences, University of Hawaii at Manoa, Honolulu, HI

Abstract Of the 44 known to occur in Hawaii, there has been limited research on Roger, Camponotus variegatus Smith, Anoplolepis gracilipes Smith, and Wasmannia auropunctata Roger; all of which were recorded as adventive species in Hawaii as early as the late 1800s to as recent as 1999. Our research focuses on the behavioral ecology of these ant species. Laboratory bioassays were performed to assess agonistic interactions of L. falcigera, C. variegatus, A. gracilipes, and W. auropunctata with the co–occurring subterranean termite, Coptotermes formosanus Shiraki. These assays will provide information on the ecological interactions and invasive biology of the four . We used a rating system based on the first two behavioral responses of each of the two paired in each individual bioassay. Following published methods used previously in our laboratory, the rating system is as follows: avoidance (-), no response (0), and aggression (+). In assays with , C. formosanus Shiraki soldiers showed an aggressive response towards L. falcigera, while a majority of no response interactions were noted in the pairings of C. formosanus with C. variegatus, A. gracilipes, and W. auropunctata. Only W. auropunctata response demonstrated aggression towards the termite soldiers.

Introduction Results The interactions between the four ant species and Of the 44 introduced ant species known to occur the termite were separated according to whether in Hawaii, there has been limited research on the interaction was initiated by the ant or the interactions among the ant species, Leptogenys termite. As shown in Table 1, C. formosanus falcigera Roger, Camponotus variegatus Smith, showed a strong ‘aggressive’ response to L. Anoplolepis gracilipes Smith, and Wasmannia falcigera, with 90% of the interactions being auropunctata Roger and their interactions with aggressive. On the other hand C. formosanus the co-occurring subterranean termite www.antweb.org/.../ casent0102271_p_1_low.jpg showed only a 5% aggressive response and 75% Coptotermes formosanus Shiraki. Anoplolepis ‘no response’ to W. auropunctata. C. formosanus gracilipes and W. auropunctata are more showed about 50:50 ‘no response’ or ‘aggressive’ prevalent in Hawaii’s natural and urban Table 1. response towards C. variegatus and A. gracilipes. environment than the other ant species, L. Percentage of C. formosanus soldiers responding to living ants Table 2 displays the responses initiated by the falcigera and C. variegatus. Interestingly L. (20 replicates per ant species) falcigera and C. variegatus were first recorded in ants toward the termite soldiers. In the majority Hawaii in the late 1800s and A. gracilipes and W. Ant Species of interactions, three ants species showed a ‘no auropunctata were discovered more recently in response’ to the presence of the termite soldier. 1952 and 1999 respectively. Perhaps the % Termite responses Wasmannia auropunctata was the only species that showed an ‘aggressive’ response in over half prevalence of A. gracilipes and W. auropunctata Avoid No response Aggressive is related to their more recent introduction into of its interactions. C. variegatus showed no Hawaii. And, perhaps the lesser occurrence of L. L. falcigera 01090response in 100% of the trials while L. falcigera falcigera and C. variegatus is due to competition C. variegatus 05545and A. gracilipes showed 70% or higher no from the more recent invading ant species. Our W. auropunctata 20 75 5 response to C. formosanus. A. gracilipes 05545 research focuses on the behavioral ecology and invasive biology of these ants. As ants are major Discussion predators of termites, we conducted laboratory C. formosanus responded differently to L. falcigera experiments to explore the relationship between than to the other three ant species, C. variegatus, A. these co-occurring enemies by assessing their gracilipes,andW. auropunctata. C. formosanus was agonistic interactions. These represent the first aggressive towards L. falcigera in 90% of the trials, Table 2. experiments in a larger study to assess the as opposed to showing no response towards the other competitive nature of these four ant species in three ant species in 50% or more of the trials. L. http://www.geographic.hu/index.php?act=napi&id=2772 Percentage of ant species responding to C. formosanus soldiers Hawaii http://tolweb.org/tree?group=Dictyoptera (20 replicates per ant species) falcigera is currently one of the rarer species occurring in Hawaii and one of the ants introduced in Ant species the late 1800’s. Perhaps the limited distribution of this ant is related to the competitive ability of Methods and Materials % Ant responses spatially co- occurring species, as shown in the Formosan subterranean termites were collected on the Avoid No response Aggressive aggressive behavior of C. formosanus. Conversely the Manoa Campus of the University of Hawaii using a other three ants, C. variegatus, A. gracilipes,andW. trapping technique (Tamashiro et al. 1973). The ant L. falcigera 25 70 5 auropunctata are more prevalent in Hawaii, and did species, Leptogenys falcigera, Camponotus C. variegatus 01000initiate less aggressive responses by the co-occurring variegatus, and Anoplolepis gracilipes were collected W. auropunctata 53560subterranean termite. A. gracilipes 09010 from the soil or within the branches or trunk of trees In terms of the ant response to the termites, the largest at an experimental farm in Waimanalo, Oahu, Hawaii. aggressive response (60%) was observed with the Wasmannia auropunctata was collected on the Island recent invader (1999) W. auropunctata, whereas A. of Hawaii in the Puna district from the soil of a flower gracilipes, C. variegatus, and L. falcigera showed no pot. response in the majority of the trials. However, ants may demonstrate a wider range of behaviors that are Agonistic bioassays between the ants and termites adequately accounted for by our rating system were conducted in a 60 X 15mm Petri dish, following (Retana and Cerda, 1994). Thus, we are currently the methods of Cornelius and Grace (1994). A conducting additional investigations of agonistic termite soldier was gently placed in a Petri dish interactions among the ant species in Hawaii to coated with fluon for a couple of minutes or until they elucidate the possible relationships between time of started to walk around. A worker of one of the four introduction to Hawaii and the invasive biology of ant species was then placed in center of the same Petri these species. dish. Responses were observed and recorded from References the perspective of both the ant and the termite, and Cornelius, L. Mary and J. K. Grace. 1994. Environmental Entomology 23: 1524-1527. recorded as avoidance (-1), no response (0), or Tamashiro, M., J. K. Fujii and P.–Y. Lai. 1973. Environmental Entomology 2: 721-722. aggression (+1). The first two interactions were Retana, J. and X. Cerda. 1995. Journal of Insect Behavior 8: 365-380. observed and the highest scored response was Acknowledgments recorded. There were 20 replications with each ant We are grateful to J. R. Yates III and R. J. Woodrow for helpful advice. Partial funding was provided by USDA-ARS Specific species. Cooperative Agreement 58-6615-4-237, and Hatch and Smyth- Lever funds administered by the College of Tropical Agriculture and Human Resources.