The Journal Volume 45: 65-75 of Research JRl on the ISSN 0022-4.S24 (print) THE LEPIDOPTERA RESEARCH FOUNDATION, 24 August 2012 ISSN 2I56-!')4.')7 (onunp)

Partitioning variation in duration of ant feeding bouts can offer insights into the palatability of : experiments on African fruit-feeding

Freerk Molleman’’^*, Ants Kaasik’, Melissa R. Whitaker^, James R. Carey‘S ' Institute of Ecology and Earth Sciences, University of Tartu, Vaneniuise 46, EE-51014 Tartu, Estonia * Department of Entomology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA ’ Department of Evolution and Ecology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA

Abstract. Quantification of chemical defence contributes to the study of signals, and to understanding trade-offs among defences and life history traits. Some tropical fruit-feeding species can be expected to have well-developed anti-predator defences because they are long-lived, are host-plant specialists, and/or have contrasting colourations that may be involved in mimicry' relationships. Yet, as a group they are often assumed to be palatable, even without supporting data. Palatability is a continuum that embraces within and between prey-species variation, and therefore, both among- and within-species variation must be documented. Palatability of nine species of fruit¬ feeding butterfly in was rated using a novel assay. One hundred and twenty-five butterflies were homogenized, their ground tissues suspended in sugar water and these suspensions offered as small dropleLs to individual ants in Petri dishes. The time ants spent feeding on the.se droplets was measured. Danaine butterflies were used as unpalatable references, and sugar solution as a palatable reference. Ants tended to eat in significandy shorter bouts from danaines compared to fruit¬ feeding species, and feeding bouts on pure sugar solution were longest Within fruit-feeding species, variation in the duration of ants’ feeding bouts was very substantial. There was also considerable variation among individual ants, such that large sample sizes would be needed to reliably distinguish palatability of different species of fruit-feeding butterflies. In explorative analy.se.s, at least three fniit- feeding butterfly species that were assumed palatable appeared to be chemically defended. These results suggest that, in contrast to common assumptions, some tropical fruit-feeding butterflies use unpalatability for defence, perhaps contributing to their long life spans in the wild.

Key words: fruit-feeding, tropical, , mimicry, colour, chemical defence

Introduction having longevity records that exceed six months (Kelson, 2008; Molleman et aL, 2007, F. Molleman Quantification of chemical defence is important unpublished data), therefore they must have effective for understanding the evolution of signals to anti-predator strategies. Chemical defence in long- predators, investments in other types of defences, lived butterflies in the tropics is demonstrated by and life history. Tropical fruit-feeding butterflies several pollen-feeding butterfly species in the genus generally have long life spans, with many species Heliconius that have long active life spans similar to fruit-feeding species (Ehrlich & Gilbert, 1973; Engler- Chaouat Sc Gilbert, 2007; Pasteels Sc Gregoire, 1983; * Corresponding author. Institute of Ecology and Earth Sciences, Turner, 1971). Such association between chemical University of Tartu, Vanemuise 46, EE-51014 Tartu, Estonia. defence and long life spans in insects was proposed freerkmolU'man ©hotmail. com by Pasteels & Gregoire (1983), and butterflies that use more chemically defended host-plants live longer on average (Beck Sc Fiedler, 2009). However, in Received: 16 March 2012 Accej)ted: 5 June 2012 this latter multi-species comparison this effect was not statistically significant (Beck & Fiedler, 2009). One potential explanation for this could be that

Copyright: This work is licensed under the Creative Commons host-plant chemistry is a poor predictor of adult Attribution-NonCommercial-NoDerivs 3.0 Unported License. To palatability given varying levels of sequestration and view a copy of this license, visit http://creativecommons.org/ de novo synthesis, and thus chemical defence would licenses/by-nc-nd/3.0/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, be better measured using the butterflies themselves USA. (Beck & Fiedler, 2009). Furthermore, many fruit- 66 J. Res.I^pid.

feeding butterflies are host-plant specialists (but not Material and methods all, notable exceptions are grass feeding Satyrines and some Charaxes; e.g. DeVries, 1987; Larsen, 1991), Study site and subjects a trait associated with the sequestration of defensive chemicals (Nishida, 2002). Moreover, chemically This study -was conducted at the Makerere defended species often signal their unprofitability University Biological Field Station in Kibale Forest to predators with visual signals such as contrasting National Park, Western Uganda. The field station colour patterns (aposematism) and these signals borders selectively logged moist evergreen forest can then be mimicked by other species that are not at an altitude of around 1500 m (Chapman et necessarily defended. Such contrasting patterns are al., 2005). Palatability tests were conducted on found in many fruit-feeding butterfly species and nine fruit-feeding butterfly species (Lepidoptera: mimicry does occur within this guild, but evidence for Nymphalidae) illustrated in Fig. 1. Three species of the nature of it (Batesian versus Mfillerian, evasiveness danaines (Lepidoptera, Nymphalidae) were included versus palatability-mediated) is scarce. Therefore, it (AmaMrarawfim (Linnaeus, 1758), Tirumalapetiverana is likely that these colours function, at least in part, (Dovxbleday 1847), T. formosa (Godman 1880)) as to signal unpalatability to predators. examples of unpalatable butterflies (Jeffords et Despite these reasons to suspect chemical defence al, 1979) including evidence for African species in fruit-feeding butterflies, in the literature only a few but not the particular species used (Larsen, 1983, species of fruit-feeding butterfly have been shown to be 1992a, 2007). The fruit-feeding butterflies included chemically defended (e. g. cyparissa: Larsen, species with brightly coloured and contrasting wing 2007)—they are typically assumed to rely on evasive uppersides {E. eusemoides Grose-Smith & Kirby 1889, flight (Larsen, 1992b; van Someren &Jackson, 1959), E. alacris Hecq 1979), one species with deep blue/ crypsis, or eye-spots (Brakefield & Reitsma, 1991; Hill violet females and metallic green males {E. kakamega & Vaca, 2004; Marini-Filho & Martins, 2010) instead van Someren 1934), and species with cryptic wing of chemical defence. It should be tested whether fruit¬ patterns { chelysY^hvicms 1793, Kallimoides feeding butterflies that can putatively be classified as rumia Westwood 1850), as well as species that are evasive (e. g. Charaxes, Euphaedra) and/or cryptic (e. g. neither particularly cryptic nor clearly warningly Kallimoides, Gnophodes) also employ chemical defence in coloured {E. medon, E. harpalyce, Harma theobene the form of unpalatability. Finally, insight into within- Doubleday 1849, CharaxesfulvescensAxir'wWWu?, 1891). species variation in palatability is of interest. Various Larvae of most of these fruit-feeding butterflies are factors have been implicated in such variation, including considered cryptic. However, Euphaedra caterpillars age, sex, larval host-plant, and genetic differences in may be imprecise mimics of stinging slug-caterpillars defence strategy (Alonso-Mejia & Brower, 1994; Brower (Limacodidae), and contrasting colours are found et al, 1982; Eggenberger et ai, 1992; Eggenberger & in the gregarious caterpillars of E. kakamega (black Rowellrahier, 1992,1993; Holloway etai, 1993; Moranz with light yellow bands: Molleman & Hecq, 2005) & Brower, 1998; Saporito et ai, 2010). and to a lesser extent in those of E. eusemoides (green The present study used the duration of feeding with dark dorsal setae: Molleman, in press). The bouts of workers of one ant species on butterfly combination of warning colours and gregariousness suspensions as a measure of butterfly palatability. clearly indicates unpalatability (Sillen-Tullberg, Warningly coloured species were hypothesized to be 1988), and this is then usually transferred to the unpalatable, and chemical defence was hypothesized to adult stage as well (Pasteels & Gregoire, 1983). The play a role in an apparent mimicry relationship within host-plants from which the studied species were reared the genus Euphaedra: E. medon Thurau 1903 females in Kibale (Table 1) belong to families from which and E. harpalyceT?L\hoi 1929 (not closely related within various unpalatable or toxic chemicals are known (e.g. the genus). Mimicry in this group has been suspected Glaudino et al, 2009; Dongo et al, 2009; Krief et al, to be based on signalling of unprofitability based on 2006; Penders & Delaude, 1994; Webber & Woodrow, evasive flight (van Someren &Jackson, 1959), but strong 2009), except for the grass feeding G. chelys, while the evidence for such mimicry is lacking (Ruxton et al, host-plant of K. rumia is still unknown. 2004). The technique used to measure palatability was convenient in a field setting under tropical conditions, Experimental methods provided values for individual butterflies, was free of prejudice based on any visual signal, was (nearly) Butterflies were either reared from field-collected independent of odour-mediated attractiveness, and caterpillars (most fruit-feeding butterfly individuals subjects could be assayed over an extended period. except K. rumia) or were collected from the field as 45: 65-75, 2012 67

adults using sweep nets (danaines) or baited traps (all Table 1. Host-plant information for the assayed butterflies others). They were killed and the legs, wings, and head in Kibale National Park, Uganda. were removed before weighing. Each specimen was then ground up with three times its weight of boiled rainwater using a mortar and pestle. The resulting Butterfly Host-plant suspension was placed in a vial. In experiment I, a species genus family second solution was prepared in another vial that Asclepiadaceae, Danainae ? contained the same amount of water as was added to Euphorbiaceae the butterfly suspension, and a ten percent sucrose Euphaedra kakamega Aphania Sapindaceae solution was added to both vials so that both had a Euphaedra alacris Aphania Sapindaceae five percent sugar concentration. One droplet of each Euphaedra eusemoides Uvariopsis Annonaceae solution/suspension (one pair per Petri dish) was then Blighia, Aphania, Euphaedra harpalyce Sapindaceae placed two centimetres apart near the centre of a Petri Pancovia dish (droplets were named ‘butterfly’ and ‘sugar’). Euphaedra medon Paullinia Sapindaceae

In experiment II, the droplet of sugar solution was Harma theobene Lmdackeria Achariaceae omitted but the butterfly suspension was prepared Charaxes fulvescens Allaphylus Sapindaceae in the same way. Kallimoides rumia ? Three ant species that were common in the vicinity Gnophodes chelys Set aria Poaceae were tested in preliminary trials, but only Myrmicaria c.f. natalensis Smith 1858 (subfamily Myrmicinae) workers walked around quietly and fed from the solutions offered, while the others tended to sit at the Data analysis edge of the petri-dish without moving or ran about frantically. M. natalensis (Smith) (Hym: Formicidae) Each ant’s first choice of droplet (butterfly vs is a large, slow-moving, predaceous ant that forms sugar) in experiment I was recorded. Ants typically large nests of up to several thousand workers (Arnold, returned to the same droplet but some switches 1924) and is very common around Kibale National were observed as well, and these were expressed as Park. Worker ants from this species were collected proportions. Statistical analyses were performed from nearby ant trails and one ant was introduced using linear mixed models on ant feeding bout into each Petri dish with a soft forceps. They were durations in R (package lme4: Bates et al., 2011), left in the Petri dish for up to 90 minutes, and were residuals showing an adequate fit of the modelling replaced after 15 minutes of inactivity. Even though approach. 'Variation among individual ants and ants may show different behavior in their natural variation among butterfly individuals of the same context than when isolated in a Petri dish, workers of species were captured with random effects, with this species appeared to be reasonably at ease in our ants nested in butterfly individual. We attempted to set up. Similar arena trials for example in bio-activity correct for possible differences among experiment tests of larval sawfly haemolymphof (Muller et al, 2002) days by using weather data as covariates for all data, and for ranking the strength of interactions within and we used the duration of feeding bouts on sugar as and between species in the context of butterfly-ant daily references (for experiment I only). To determine mutualism (e.g. Ballmer & Pratt, 1991; Burghardt & whether a pooled analysis of data from experiments I Fiedler, 1996) have proven to be highly useful. and II was appropriate (the only difference between Observations were made by teams of two to five them being the presence/absence of the sugar local technicians. Each person could simultaneously droplet), we compared distributions of durations of observe up to six Petri dishes, each containing one two butterfly species that were well represented in pair of droplets (or one droplet in experiment II) and both data sets, and compared species effect estimates one ant, while one person recorded the data. Start between separate analyses of experiments I and II. and end times for each ant feeding bout were noted First, we tested whether fruit-feeding butterflies as in seconds. Local weather data were used to control a group could be distinguished from the references for any temperature effect. Experiment I was first (danaines and sugar solution) using one-tailed tests. supervised by EM (May-June 2007), was then carried Second, we tested whether there were significant on without supervision, and was later supervised differences among the fruit-feeding butterflies by MRW (July-August 2008). Experiment II was using a two-tailed test. Lastly, effect estimates for performed by local technicians without supervision butterfly species were calculated and compared to (September 2008-July 2009). the references using one-tailed tests. To compare 68 J. Res.Ixpid.

Figure 1: Photographs of butterfly species on which palatability tests were conducted, a. Euphaedra eusemoides female, b. Charaxes fulvescensma\e. c. E. a/acr/s female, d. E. harpa/yce female, e. E. medon female, f. E./ca/camega caterpillars, g. E./ca/camega female, h. E./ca/camega male. i. E.medon male. j. Gnophodes chelys female, k. Harma theobene male. I. Kallimoides rumia male.

durations of feeding bouts on butterfly suspension Results with those on sugar solution while using durations on sugar to correct for day effects, the feeding bout Experiment I yielded data from 57 butterflies (9 durations on sugar were subtracted from those on species), and experiment 11 from 68 butterflies (8 butterfly, and were then tested for equality with zero species) and the pooled data involved 663 feeding (data from experiment I only). ants. The first choice of ants was biased towards 45: 65-75, 2012 69

butterfly suspension for all species, including is up to 1.06 higher or lower than the average for danaines. Switching occurred mostly from sugar to the species, which is a lot because species estimates butterfly, except for danaines, E. kakamega, and H. range between 3.23 and 4.35. The magnitude of the theobene (Table 2). within- species variation can be illustrated further Feeding bout durations were seemingly gamma using E. harpalyce where the interval that includes distributed, ranging from a few seconds to about 10 about 95% of the individuals is 62 to 520 seconds. minutes. Log transformation produced a normally It was problematic to include butterfly age (freshly distributed response variable that was used for all emerged vs field collected) into the model, because of subsequent analyses and the graphical representation. unequal distribution among species and small sample Modelling log-transformed data using the normal sizes. Graphical representation did not suggest any distribution corresponds to the (untransformed) correlation between age (freshly eclosed vs field data being from the log-normal distribution. The collected) and palatability. For the species with the interval for the mean feeding bout duration within largest sample size {C. fulvescens) no significant age a species could, therefore, be estimated while taking effect was detected either. Moreover, no sex effect was into account the residual variation in the model. For found in our data, and including our weather data species that were well represented in both datasets, the did not improve our models. The variation among distribution of durations of feeding bouts on butterfly individual ants was also substantial with an SD for droplets were very similar (Kolmogorov-Smirnov the pooled data of 0.37 (Table 3). No effect of order 0=0.11, 0.42 for £. a/acraand 0 = 0.10,/>= 0.24 for C. number of feeding of individual ants was detected. fulvescens). Moreover, the estimates for species effects The analysis of feeding bout durations on pure were similar among the two experiments (Table 3). sugar showed that feeding bout durations differed Therefore, it wasjustified to combine the data sets for among days, and a similar pattern was detected this response variable. within the butterfly species such that there was a Within-species variation was extensive (Fig. correlation between feeding bout durations on 2). Because the random effects are assumed to be sugar and butterfly on particular days. However, normally distributed, we can analyze this variation in daily maximum temperature was not correlated with detail. For example, in the analysis of pooled data ant feeding bout duration on sugar. Sugar solution (Table 3), the standard deviation for the butterfly was only used in experiment 1, and for these data random effect was 0.54, meaning that for each species, correcting for such day effects by including durations individuals have a high probability of an average that on sugar as a co-factor improved the performance of

Figure 2. Palatability of butterfly species measured as duration of individual feeding bouts of ants (feedings) on butterfly suspensions (number of freshly emerged and field collected butterflies used). Box-plots represent averages among individual butterflies that are in turn based on varying numbers of feeding bouts with median, quartiles, and full range. The vertical dotted line represents the average duration of feeding bouts on sugar solution.

# fresh/field # feedings 0/11 116 Danainae -1 26/4 448 Charaxes fulvescens -1 1 4/0 73 Euphaedra kakamega 1 1- -1 n.... 13/5 287 Euphaedra alacris -J1 1 1 5/1 76 Euphaedra eusemoides -1 1 1- 3/6 189 Euphaedra harpalyce 1- --1 4/13 385 Euphaedra medon -1 1 6/7 162 Harma theobene -II 0/9 136 Kallimoides rumia -1 1 \- 6/2 121 Gnophodes chelys LL.

r X T X T X "1 1 2 3 4 5 6 7 mean log time (in seconds) 70 J. ResJ^pid.

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the statistical test. Nevertheless, pooled analyses for type of chemical defence most effective to different comparing fruit-feeding butterflies to danaines and classes of predators have been noted as well. For to sugar solution remained preferred because of the example, Paederus beetle larvae produce pederin as a larger sample size. defense against spiders, which is not effective against Ant feeding bouts were shortest for danaine other (Kellner & Dettner, 1996). While specimens on average (Fig. 2), and as a group, fruit¬ realizing the need for further tests, we interpret feeding butterflies could be distinguished from shorter feeding bouts of ants as indicative of lower them (random effects model,/?<0.001). On average, palatability to most generalist predators. sugar was fed on for longer bouts than the fruit¬ The first droplet that ants fed on was usually feeding butterflies combined (random effects model, butterfly suspension, which may represent a preference p=0.021). Some fruit-feeding butterfly species were or simply an effect of detectability as the butterfly fed on for shorter bouts than others on average (Fig. suspension may emit a stronger odour. Therefore, 2), but these differences were not significant (random cafeteria experiments where ants choose between effects model excluding danaine and sugar data, food sources do not measure only palatability, but also p=0.bA). In exploratory analyses (without correcting detectability. Ants’ switching behaviour was consistent for multiple testing) E. harpalyce, E. medon, and H. with the results of feeding bout durations: butterfly theobene could be distinguished from sugar (Table species that were fed on for short feeding bouts were 2), and E. kakarnega could not be distinguished from also more often switched away from. danaines (Table 3). However, non-significance is The duration of ant feeding bouts varied attributable to low sample sizes, and estimates of the considerably for individual butterflies of the same number of feeding bouts that need to be measured to species and for individual ants. However, in our data statistically distinguish the species from the assayed we did not find within-species correlations between danaines (N*) may be best suited to preliminarily ant feeding bout durations and butterfly age or sex. rank the species according to palatability. This Apart from variation in defensive chemistry, variation suggests that E. harpalyce and E. medon are least in nutritional value (depending on reproductive palatable, followed by /?. kakarnega (Table 3). history and nutritional status of the individual butterfly) could also have contributed to this within- Discussion species variation in palatability albeit mainly in the minority of butterflies that had been field-captured. We showed that certain African fruit-feeding Ant behaviour could vary according to local climate, butterflies can be moderately unpalatable to ants, and lineage-specific traits, as well as nutritional status of documented extensive variation in palatability within the colony or individual (e. g. whether an individual butterfly species. To interpret colour patterns and was going out to forage or was coming back with discover trade-offs with other defences and life history food). However, the nutritional status of individual traits, it would be useful to know the palatability ants did not appear to affect feeding bout duration of butterflies to the relevant predators. However, because the order number of feeding of individual observations of predation on fruit-feeding butterflies ants did not affect it. in the wild are extremely rare. If natural predators are When feeding bout durations on sugar droplets visual hunting vertebrates (e.g. birds and lizards) as could be used as reference for observation days, some can be suspected, it can be hard to obtain palatability of this variation could be accounted for, leading to values for individual prey items that are unbiased by greater power for distinguishing butterfly species. prey appearance and predator experience. Hence, This suggests that day-to-day variation in our data is assays with insects such as ants are useful (e. g. Eisner mainly caused by weather, despite lack of correlation et al., 2008). Given the diversity of potential predators with the daily maximum temperature. in tropical forests, we expect that tropical butterflies Based on the duration of ant feeding bouts, fruit¬ that depend on unpalatability for survival should be feeding butterflies are on average more palatable than distasteful to a wide range of predators, including danaines. As a group fruit-feeding butterflies could ants. Moreover, congruence among predator be distinguished from the danaines, and all except species in their responses to defensive chemicals is E. kakarnega were distinguishable in the exploratory usually substantial (Pasteels & Gregoire, 1983). For analysis. The interpretation of tests against the pure example, hornets, cats and humans ranked the taste sugar solution is less straightforward because the of bird meat similarly (Gott, 1947). However, rarely is sugar solution offers only sugar and water, while the palatability of butterflies rated using more than one butterfly suspension offers the ants the same sugar potential predator (Trigo, 2000), and differences in concentration, but with added nutrients as well as 45: 65-75, 2012 73

defensive chemicals from the butterfly. Thus, the interest, and therefore, assays that produce palatability value of a sugar control may lay primarily in its role estimates for individuals are preferred over those in accounting for variation in ant behaviour. While, that yield only a population mean with confidence as a group, fruit-feeding butterflies were fed on for interval. Given that there is a gradient rather than significantly shorter bouts than pure sugar solution, a dichotomy of palatability (Brower et al., 1968), differences for several species were small and only continuous measures such as feeding bout durations three fruit-feeding species (E. harpalyce, E. medon, and more readily provide statistically significant results. H. theobene) were distinguished in the exploratory Using common omnivorous and easy-to-handle ants, analysis. we presented such a method, that is convenient in a Results of the exploratory analyses are biologically field-lab setting (also in tropical regions) and requires interpretable. The similarity between E. medon little training. females and E. harpalyce may be an example of However, we suggest several improvements to the Mullerian mimicry, because both species were less method presented. Responses of used in assays palatable than sugar solution and were the hardest vary over time and among individuals and lineages, to distinguish from Danaines (N* 142 and 111 and this can to be countered by; 1) using positive and feedings, respectively). E. kakamega also appeared negative controls with each test, preferably for each to be unpalatable, and this is not surprising because ant; 2) using worker ants from several documented of its warningly coloured gregarious caterpillars. colonies; 3) only picking individuals that leave the The adult dorsal wing colouration is also non- colony on a foraging trail; and 4) recording local cryptic and may be mimicked by other species, most conditions (e.g. temperature and humidity for each notably £. Uganda (Aurivillius 1895). H. theobene assay). While a sugar solution is a straightforward also distinguished from sugar in the exploratory palatable control, a more standard negative control analyses but appeared more easily distinguished from would be preferable. If a freezer is available, a stock danaines. Any chemical defence in this species may suspension made from a large number of known be related to the suspected sequestration of host-plant unpalatable insects could serve as such. However, chemicals (probably cyanides) in this group (van to compare palatability among different regions, a Velzen et al., 2007), but is surprising in the light of global standard of‘mixed defensive chemicals’, needs its rather cryptic appearance. This may demonstrate to be developed. Animals behave differently towards that chemical defence is not always advertised with potential food in a natural setting than when isolated contrasting colour patterns (Endler & Mappes, in a Petri dish. With video cameras ant feeding 2004). We have noted adverse reactions to other bouts could be recorded in cafetaria experiments cryptic fruit-feeding butterflies (Molleman et al. 2010) in a natural setting. It can be expected that a much but this did not bear out in our analyses of feeding wider range of ant species would be amendable for bout durations. On the other hand, contrastingly such approach. This is important when attempting coloured species E. alacris and E. eusemoides did not to measure feeding bout durations where such docile appear to be particularly unpalatable, and these are ants are not available, and also to test for congruence more likely Batesian mimics of chemically defended in the responses of multiple ant species. Moreover, moths. However, all such hypotheses on particular with video images it would be easier to code transient species generated by our exploratory analyses need behaviours such as running away from food and to be tested with further palatability assays, and, most grooming, and to distinguish between active feeding critically, observations on avoidance behaviour of and resting at the food. While it remains to be shown potential predators such as birds and chameleons. that other ant species also adapt their feeding bout Nevertheless, our results indicate that one cannot durations according to palatability of the food, we assume that fruit-feeding butterflies are all equally believe that this parameter is a relatively efficient palatable, despite strongly developed evasive flight metric for ranking the palatability of animals. and crypsis in this group.

Obtaining palatability data needed to elucidate Acknowledgements the evolution of defence and signals such as colour patterns, and their relationship to life history We thank Boniface Balyeganira, Harriet Kesiiine, Christopher evolution is challenging. It is important to distinguish Aliganyira, Francis Katurainu Kanywanii, John Koojo, Francis between tests that measure (innate or learned) Akoch Ecligu, Malgorzata E. Arlet and Mary Alum, for their invaluable assistance in the field and in the laboratory. Weather responses to appearance, odour, palatability, toxicity, data were kindly provided by Colin and Lauren Chapman. We or a combination of these. Moreover, variation thank Torben Larsen for sending us important literature, Phil within species may also be extensive and of biological Ward for identifying our ant samples and Johanna Mappes, 74 J. Res.I^pid.

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