BIOLOGICAL AND MICROBIAL CONTROL Functional Response of the Tiger Beetle Megacephala carolina carolina (Coleoptera: Carabidae) on Twolined Spittlebug (Hemiptera: Cercopidae) and Fall Armyworm (Lepidoptera: Noctuidae) 1 2 PUNYA NACHAPPA, S. K. BRAMAN, L. P. GUILLEBEAU, AND J. N. ALL Department of Entomology, University of Georgia, Athens, GA 30602 J. Econ. Entomol. 99(5): 1583Ð1589 (2006) ABSTRACT The functional response of the tiger beetle Megacephala carolina carolina L. (Co- leoptera: Carabidae) was determined on adult twolined spittlebug, Prosapia bicincta (Say) (Hemiptera: Cercopidae), and fourth instars of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), in single-prey and two-prey systems. In the laboratory, M. carolina carolina demonstrated a type II functional response for P. bicincta and S. frugiperda in both single- and two-prey systems. Search efÞciency of M. carolina declined for both prey as the initial number of prey increased. Of the total prey consumed, M. carolina carolina killed signiÞcantly more S. frugiperda than P. bicincta in the single-prey system (8.0 and 4.5, respectively) and the two-prey system (5.0 and 2.0, respec- tively). Estimates of attack coefÞcient, a, were not signiÞcantly different for P. bicincta and S. frugiperda in the single-prey (0.07 and 0.02) and two-prey systems (0.04 and 0.06), respectively. The handling time, Th, was signiÞcantly greater for P. bicincta (5.02 and 10.64 h) than for S. frugiperda (2.66 and 4.41 h) in single- and two-prey systems, respectively. Estimations of attack coefÞcient and handling time in the single-prey system were used to predict prey preference of M. carolina carolina. No strong prey switching response was observed. M. carolina carolina showed no preference for either prey. However, in the presence of S. frugiperda, the functional response of the predator for P. bicincta was reduced. M. carolina carolina is a potential predator of one or more turfgrass pests and should be considered in conservation efforts. KEY WORDS Megacephala carolina carolina, Prosapia bicincta, Spodoptera frugiperda, turfgrass, biological control Managed landscapes have a diversity of plants and of twolined spittlebugs (Fagan and Kuitert 1969). Spo- associated arthropod pests (Potter and Braman 1991, doptera frugiperda (J.E. Smith) (Lepidoptera: Noctu- Vittum et al. 1999). Additionally, urban landscapes idae), the fall armyworm, is a sporadic pest of turf- have a wealth of beneÞcial arthropods, including cara- grasses especially in southeastern United States and bids (e.g., tiger beetles), staphylinids, mites, spiders, Canada (Vittum et al. 1999). The larva is the injurious and ants (Reinert 1978; CockÞeld and Potter 1983, stage and has a variety of hosts, but it prefers grasses. 1984; Braman and Pendley 1993; Braman et al. 2000). The larvae feed on all aboveground plant parts (Cobb These entomophagous invertebrates help limit pest 1995). outbreaks in urban landscapes (Reinert 1978, Cock- The tiger beetle, Megacephala carolina carolina L. Þeld and Potter 1984, Terry et al. 1993). (Coleoptera: Carabidae), is a nocturnal predator Prosapia bicincta (Say) (Hemiptera: Cercopidae), found throughout southeastern United States (Graves the twolined spittlebug, is an injurious and widespread and Pearson 1973, Pearson 1988). Tiger beetles have pest of turfgrasses and ornamentals in southeastern been captured in open areas, mud ßats, lighted areas, United States (Beard 1973, Braman 1995, Vittum et al. shores of ponds, and woodland paths. Braman et al. 1999). Twolined spittlebug nymphs and adults are (2002, 2003) reported M. carolina carolina collected in opportunistic xylem feeders and can feed on plants pitfall trap samples in turfgrasses and landscapes. M. that provide ßuids to meet their requirements (Pass carolina carolina has been shown to be a promising and Reed 1965). There are few known natural enemies predator of P. bicincta adults (Nachappa et al. 2006). Functional response relates change in predation rates to increasing prey density (Holling 1959). Func- 1 Current address: Department of Entomology, Kansas State Uni- versity, 123 West Waters Hall, Manhattan, KS 66506Ð4004. tional response can be used to determine whether a 2 Corresponding author, e-mail: kbraman@grifÞn.uga.edu. predator is able to regulate the density of its prey when 0022-0493/06/1583Ð1589$04.00/0 ᭧ 2006 Entomological Society of America 1584 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 99, no. 5 the response depends on density (Murdoch and Oaten viron, Manitoba, Canada) and maintained at 24ЊC, 1975). By their shape Holling (1959) described three 75Ð80% RH, and a photoperiod of 15:9 (L:D) h. Adult predator functional responses in which the number of P. bicincta were used for the experiments. prey consumed rises linearly, hyperbolically, or sig- Fourth instars of S. frugiperda were obtained from moidally, for a type I, type II, and type III response, a laboratory-reared colony. S. frugiperda eggs were respectively. Most invertebrate predators demon- obtained from USDAÐARS Crop protection and Man- strate type II response, whereas the type III is exhib- agement Research Unit in Tifton, GA. Neonate fall ited by both vertebrate and invertebrate predators armyworms were maintained on commercial diet (Riechert and Lockley 1984). (Bio-Serve, Frenchtown, NJ) in 32-ml diet cups, and The effects of alternative prey on the population placed in environmental chambers (Percival Scien- dynamics of target prey and predator have focused on tiÞc, Perry, IA) at 24ЊC, 75Ð80% RH, and a photoperiod functional and numerical responses (Eubanks and of 15:9 (L:D) h. Fourth instars of S. frugiperda larvae Denno 2000). The primary effect of alternative prey were used for experiments. on the functional response is the decrease in the con- Experimental Design. All experiments were con- sumption of the target prey due to prey switching or ducted at room temperature (24 Ϯ 1ЊC) under ßuo- saturation (Murdoch 1969). However, the target prey rescent light set at a light cycle of 14:10 (L:D) h, and also can have a positive effect on biological control by relative humidity was maintained at 70%. Experimen- increasing the predatorÕs numerical response (Settle tal arenas consisted of 18.0- by 8.0-cm plastic cages et al. 1996). (Pioneer Plastics, Dixon, KY), with 254.34-cm2 total In summary, the ability of a predator to control a surface area. Centipedegrass (13.2 g) was provided in prey population is dependent on the predator func- the cage to simulate a more natural situation and thus tional and numerical response. However, these re- produce a functional response curve that is more Þeld sponses are inßuenced by several factors, including applicable. Tiger beetles were held without food for the density-dependent behavioral patterns, develop- 4 d before placing in the cage with prey. Preliminary mental response, prey preference, use of alternative studies showed that M. carolina carolina prey con- prey, and predatorÕs interaction with other predators. sumption was maximum 4 d after starvation. One, 3, 5, Still, scientists involved in biological control programs 7, and 11 adult P. bicincta were placed in a cage with determine the potential of a natural enemy by using a single tiger beetle. Fourth instars of S. frugiperda functional response studies with an individual preda- larvae were placed in a cage with a single tiger beetle tor/parasitoid feeding on a single patch of prey species at similar prey densities (1, 3, 5, 7, and 11) and addition (Flinn et al. 1985, De Clercq et al. 1998, Wells and of prey densities nine and 15. There were 10 replicates McPherson 1999, Lester et al. 2000, Lester and Harm- for both P. bicincta and S. frugiperda at each prey sen 2002, Stewart et al. 2002). In our study, the func- density. Controls were maintained for both prey spe- tional response, handling time, and attack coefÞcient cies separately without the predator. The experiment of M. carolina carolina on P. bicincta adults and fourth was conducted simultaneously for both P. bicincta and instar S. frugiperda larvae were determined when prey S. frugiperda as prey at each prey density. After 24 h, items were offered alone (single-prey) or simulta- the predator was removed from the cage, and the neously (two-prey system) in the same arena. We number of live prey was determined. chose these two prey types because of their obvious Prey Preference. To determine the predator func- morphological differences which might affect the tional response in the presence of two prey types, both functional response parameters (attack coefÞcient P. bicincta adults and fourth instars of S. frugiperda and handling time) and prey preference. Moreover, were placed with a single predator in a plastic cage. both insects and the predator inhabit turfgrass and Prey preference experiments were conducted under landscapes as their common habitat. the same conditions as those described above. Tests were conducted using one, three, Þve, and seven adult P. bicincta and similar numbers of fourth instars of S. Materials and Methods frugiperda in each cage; hence, a total of two, six, 10, Insect Source. Adult tiger beetles were collected and 14 of both prey types per plastic cage. The ex- from pitfall traps inserted in centipedegrass, Eremo- periment had 10 replicates at each prey density and chloa ophiuroides (Munro) Hack. and fescue, Festuca was conducted simultaneously for all replicates. Con- arundinaceae Schreb, plots in GrifÞn, GA. Beetles trols had no predator present. were maintained in 10-cm-diameter petri dishes at Statistical Analysis. Data on the prey killed at each room temperature and a photoperiod of 14:10 (L:D) prey density in single- and two-prey systems were h, and they were fed varying prey items such as Þeld analyzed using PROC GLM procedure (SAS Institute crickets, Gryllus rubens Scudder, as food. P. bicincta 2001). The most effective way to distinguish type of adults were Þeld-collected from local residential areas functional response involves performing a logistic re- and commercial landscapes from June to September gression of the proportion of prey killed related to around GrifÞn.