Australian Journal of Entomology (2002) 41, 300–305

Visual mate-searching behaviour in the evening brown butterfly, leda (L.) (: )

Darrell J Kemp

Department of Biology, Arizona State University, Tempe, USA and School of Tropical Biology, James Cook University, Cairns, Australia.

Abstract As in most , male are generally the more proactive sex with respect to seeking out mating opportunities. In most cases, males conduct their search sometime between mid-morning and mid-afternoon, but a few species are active only before dawn or after sunset. These crepuscular species offer a good opportunity to study how males deal with markedly different visual and thermal conditions. Here, I present data from a 5-month behavioural study of male (Nymphalidae) at a mate- encounter site in tropical Australia. Males of this species defended perching locations along a forest edge in a similar manner to other diurnally active territorial nymphalids. They generally arrived at these sites after sunset and arrived earlier on evenings that darkened earlier. Actively mate-locating males were only seen at the site during a 25–35 min evening period, during which ambient light levels ranged between 50 and 2600 lux. Only 27% of marked territory residents were recorded again at their location of capture, but fidelity in this ‘resighted’ group ranged up to 23 days. A sample of males, captured under ambient temperatures of 24.0–27.2°C, maintained a mean thoracic excess of 8.25 ± 0.73°C, but did not appear to ‘shiver’ in the manner of other crepuscular species. Males courted conspecific females and one mating was observed. This species is an excellent candidate for further research into the evolution of mating tactics in crepuscular butterflies. Key words crepuscular, Lepidoptera, mate location, mating strategy, sexual selection.

INTRODUCTION encounter sites); (ii) when males are active at mate encounter sites; (iii) whether males perch or patrol around an encounter Reproductive investment theory (Trivers 1972) posits that site; (iv) whether males return to the same location on members of the sex that makes the smaller overall parental successive days (site fidelity); and (v) whether males defend investment will be obliged to compete amongst themselves specific locations against conspecifics. Although these factors for access to mating opportunities. Because males often make are not strictly independent (see Dennis & Shreeve 1988), a smaller initial material investment (as a result of ani- this classification provides a useful framework by which to sogamy, Bateman 1948), and invest relatively less thereafter, conduct intraspecific comparisons and analyse the evolution- they are generally the sexually competitive sex (but see ary and ecological influences on mate-searching behaviour in Jiggins et al. 2000). Males are therefore typically subject to animals. sexual selection for the ability to out-compete their rivals and One view of the evolution of mating systems is that thus gain disproportionate access to fertilisable female the spatiotemporal distribution of receptive females (when gametes (Andersson 1994). In many species, particularly they first become predictable) will ultimately determine where , an important target of this selection is a male’s and when males should focus their search efforts (Wickman ability to locate receptive females before his rivals do. & Rutowski 1999). The specifics of male behaviour at these Our understanding of how sexual selection can mould the times and places (factors iii–v of Rutowski 1991) are then mate-locating behaviour of male animals has been greatly expected to be shaped by ecological factors such as the enhanced by the study of butterflies (e.g., Alcock & O’Neill thermal (Wickman 1985) and visual (Dennis & Shreeve 1986). Male butterflies are generally more proactive in 1988; Ravenscroft 1994) environments and conspecific male finding receptive mates, but different species, and different density (Alcock & O’Neill 1986). Because female butterflies individuals within a species, achieve this through a range of are detected visually (Vane-Wright & Boppré 1993), males tactics. In a recent analysis of this behavioural diversity, should favour search locations where their visual opportun- Rutowski (1991) classified male tactics with respect to five ities are maximised, which may favour the evolution of factors: (i) where males search for mates (= the location of perching, site fidelity and defence (Dennis & Shreeve 1988; Ravenscroft 1994). Moreover, extended patrolling may be Email: [email protected] constrained by suboptimal temperatures (Wickman 1985),

Mate location in Melanitis 301 and thermal concerns are also relevant to the behaviour of reported larval food-plants of M. leda (Common & Water- perching individuals (Rutowski et al. 1994). house 1981), grew extensively along the site. Crepuscular species of butterflies have been largely over- looked in behavioural studies (although see Freitas et al. 1997; Srygley & Penz 1999). Individuals of these species are Behavioural observations active only at either dawn or dusk, usually at times before sunrise or after sunset. A mate-locating crepuscular male is I observed territorial male M. leda on 60 evenings between therefore subject to a set of thermal and visual conditions that 8 December 2000 and 8 May 2001, and once at dawn on vary markedly from those experienced by most other butter- 25 March 2001 (when evening counts of Melanitis at the site flies. Among the truly crepuscular butterflies (excluding were at a maximum). On each evening, I arrived at the site late-afternoon species such as Vanessa atalanta L.; Bitzer & approximately 5 min prior to sunset, and noted the time at Shaw 1995), the only species that have received any serious which the first male arrived and began exhibiting territorial attention are the butterflies Caligo idomenaeus Staudinger behaviour (see below). I measured the ambient light intensity (Freitas et al. 1997), C. illioneus Butler and C. oileus (Bois- (to the nearest 10 lux) upon my arrival at the site and at duval) (Srygley & Penz 1999). Caligo idomenaeus defends approximately 10-min intervals thereafter using a LX-101 dispersed, non-resource-based territories in for a brief model digital lux meter (Lutron, Taiwan). The meter was period (15 min) at dawn, while in Panama, C. illioneus and situated in the adjacent field approximately 30 m west from C. oileus defend similar perching sites at both dawn and dusk the forest edge, and thus measured the ambient light under (Srygley & Penz 1999). Caligo species have the ability to a largely open sky. I also measured the light intensity at elevate their body temperature above the cool ambient con- the time of arrival of the first territorial male. Because of ditions by shivering (Srygley 1994). While this work has the location of the light meter, there was a 10–15 s delay provided some valuable insights, little is known about the between first male sightings and light readings; hence these mate-locating behaviour (and thermal ecology) of crepus- light values are slight underestimates. cular species outside this brassoline genus. For each territorial male that arrived at the 40 m stretch of In this paper, I present the results of a 5-month study of forest edge, I recorded his arrival time, seasonal wing pheno- mate location in the satyrine Melanitis leda (L.) type and age. Melanitis leda exhibits seasonal colour plastic- (the evening brown) at a field site in tropical Australia. ity that enables unambiguous classification of wet- and dry- This species is noted for its crepuscular habits and anecdotal season forms (Brakefield 1987), even when the wings are reports suggest that males practice territorial perching worn. I measured age on a three-point discrete scale based behaviour (see reports in McCubbin 1971; Parsons 1999; upon wing wear. These assessments utilised the extent of Braby 2000). The aims of my study were to investigate this fading of dark wing sections (equivalent to systematic scale behaviour within the context of the classification of Rutowski loss) and fraying of wing margins, rather than larger chips (1991) and to gain preliminary data on the thermal ecology of that could represent one-off incidents. The classes were: males at mate-encounter sites. (i) fresh: no fading or fraying of wing margins; (ii) moderately worn: few to several chips and/or marks, limited feathering and some lost scales; and (iii) worn: significant wing chip- ping and widespread fraying, extreme fading. In addition, I MATERIALS AND METHODS netted 40 resident males from the site and marked them, prior to release, with a small identifying symbol using Swan liquid Study site paper (Jasco, Meadowbank, NSW, Australia). I measured the This study was conducted at a site adjacent to Freshwater length of each captured male’s forewing to the nearest Creek, near Cairns in north Queensland, Australia (16°53′S, 0.5 mm. Wing-length is widely used as a surrogate measure 145°45′E). This location has been used previously for studies for body size in butterflies (e.g., Kemp 2000 and references of butterfly mating behaviour, and is described elsewhere therein). Regardless of handling, freshly liberated male M. leda (see Kemp 2001; Kemp & Rutowski 2001). The main abandon their sites immediately, so I caught residents at the structural feature is Freshwater Creek and its associated very end of each evening’s observation period to reduce riparian rainforest vegetation, which abuts a large cultivated disruption to natural behavioural regimes. sugarcane (Saccharum hybrids) field. An access track During each evening’s observation period, I took qualita- (5–15 m wide; see Kemp & Rutowski 2001) separating the tive notes on male behaviour and male–female interactions. sugarcane and creek-side vegetation forms an open corridor, Females can be distinguished from males of this species on which is a common perching site for mate-locating nympha- the basis of their larger size and more extensive orange lids such as Hypolimnas bolina (L.) (Kemp & Rutowski forewing markings (Common & Waterhouse 1981; Braby 2001). During this study, the sugarcane field was unplanted 2000). Observation was terminated when all males left the and thus the riparian vegetation gave way suddenly to site or when it became so dark (usually <100 lux) that the 2–3 km of open field. I targeted a 40-m section of the forest remaining male M. leda failed to respond to thrown pebbles. edge along which perching male M. leda frequented in the Evening observation periods therefore typically lasted evenings. Sugarcane and blady grass ( sp.), both 40–50 min.

302 DJ Kemp

Body-temperature measurements RESULTS I sampled territorial males for body-temperature determina- General male behaviour tions on four evenings, 29–31 December and 5 January, at similar forest-edge habitat approximately 5 km away from Males at the site behaved in ways reminiscent of other the Freshwater site (to avoid disturbance to marked males). territorial male nymphalid butterflies (e.g., Asterocampa leilia The thermal measuring apparatus consisted of a 40-gauge Edwards: Rutowski & Gilchrist 1988; H. bolina: Kemp 2001). copper-constantan thermocouple (Dural, Auburn, NSW, When not interacting with conspecifics or other insects, Australia) seated within a 29-gauge hypodermic needle individuals stationed themselves on perches facing out (Becton Dickenson, North Ryde, NSW, Australia), which was toward the open field (i.e., facing westward). Typically these connected to a TC-1000 digital thermocouple thermometer perches were tree leaves, stumps and branches, but males (Sable Systems, Henderson, NV, USA). I caught males and occasionally perched upon the apices of tall curving grass quickly restrained them in the net against a polystyrene sheet blades (Imperata sp.). In all cases these perches were 1–2 m prior to inserting the probe 2–3 mm into the ventral thoracic off the ground. Perching males launched themselves at passing objects, region. Peak temperature was then read to the nearest 0.1°C and I also immediately measured the ambient temperature at such as butterflies, birds and other insects. Thrown pebbles the point of capture of the male using an additional thermo- could also elicit this response. If the object was not a couple probe (specifications as above). These thermocouple conspecific, then the male M. leda would typically return to his perch or to a nearby location. On some occasions, males probes were earlier calibrated over the range of 20–50°C against a certified mercury thermometer using a Grant model spontaneously flew from their perches and patrolled along heater-stirrer (Grant Instruments, Shepreth, Cambridgeshire, the forest edge in their immediate vicinity (5–15 m) before UK) in a 15-L water bath. Only measurements obtained returning. If two mate-locating males met, then a conspic- within approximately 6 s of capture were retained for analy- uous interaction ensued, after which a single male returned to sis. I sampled males in two situations: when they were the perching site (these interactions will be described in perching on vegetation and when they were engaged in a detail in a forthcoming paper). Males therefore defended ‘diving’ aerial interaction with another male. These interac- their sites against conspecifics in the manner of other terri- tions involve relatively low intensity (low wing-beat fre- torial perching butterflies (e.g., Rutowski & Gilchrist 1988; quency) flight, but immediately follow an initial (5–10 s Kemp & Rutowski 2001). If a male met a female, then she long) high-intensity spiralling contest phase. More informa- was courted (see later). tion regarding contest behaviour will be presented elsewhere. Territorial residency patterns Statistical analysis For most of the study period, territorial males did not arrive I calculated solar altitude angle (SA) for various sampling at the site until after sunset (mean SA at time of first male dates and times using the formula: arrival = –2.2 ± 0.6°, n = 50). However, in December cen- suses males began arriving up to 20 min prior to sunset SA = arcsin ([cos (16°53′) × cos (δ) × cos (H)] (1) (Fig. 1). Ambient light at the time of early male arrival + [sin (16°53′) × sin (δ)]) ranged from 348 to 2580 lux (mean = 1095 ± 291 lux, n = 50). where δ represents the declination of the sun, calculated as: Variation in SA at the time of first male arrival was signifi- cantly negatively related to predicted ambient light intensity δ = 23.45 × sin [360/365 × (284 + day of year)] (2) at sunset (Pearson r = –0.53, n = 48, P < 0.001), which shows and H represents the hour angle, calculated as: that males arrived earlier on evenings that darkened earlier. Although males were sometimes active prior to sunset, they H = (minutes before noon)/4 (3) never perched at times when the site was exposed to direct The sunset time for specific days was calculated by letting sunlight. Individuals generally left the site 25–35 min after SA equal 0 and solving equation 1 for H, then solving the time of first male arrival, and no male was seen actively equation 3 to yield the number of minutes before noon (for mate-locating at the site by the time light levels reached the sunset value of H). I also regressed the log-transformed approximately 50 lux. Also, not a single Melanitis was seen light level against the solar angle for each evening’s observa- in the sunrise census (26 March), even though weather tion period, and used these exponential models to predict conditions were fine at this time (i.e., clear sky and light ambient light intensities at sunset. All statistical analyses wind). I counted 11 territory residents at the site that evening, were carried out using the STATISTICA (release 4.5) package and eight residents the evening before. (Statsoft, Melbourne, Australia) and quoted means through- Of the 40 individual males marked, 26 were fresh, eight out are accompanied by 95% confidence intervals. Statistical were moderately worn and six were worn. All but six were of power (the probability of obtaining a significant result; 1-β) the wet-season (WS) phenotype. Wet-season forms were was estimated using the techniques and power tables of smaller than captured dry-season (DS) forms (mean size: Cohen (1988), using a medium-effect size where necessary WS = 34.5 ± 0.3 mm; DS = 38.4 ± 0.3 mm; independent t-test, (i.e., r = 0.30). t38 = 5.41, P < 0.0001) and also younger, based upon wing

Mate location in Melanitis 303

Fig. 1. () Time of first terri- torial male arrival at the site in relation to (—) sunset. Sunset time is defined as the evening time at which the solar angle equals zero.

wear (median age: WS = ‘fresh’; DS = ‘worn’; Mann–Whitney Male–female interactions U-test = 31.0, n = 34, n = 6, P < 0.01). 1 2 I counted a total of 19 females throughout this study and timed six male–female interactions. Females were conspic- Territorial site fidelity uous because of their lighter wing colour and (in all cases except one, see below) their oviposition behaviour. This Only 11 marked males were resighted at least once sub- behaviour was very similar to that of other ovipositing sequent to their capture. A logistic regression analysis of nymphalids (e.g., H. bolina: Kemp 1998), and two female the probability of resighting, including wing length, age M. leda were seen to deposit eggs upon grass blades (Imper- and phenotype as independent variables, was not significant ata sp.) within the site. I timed five interactions between a χ 2 = 2.7, n = 40, P = 0.44). Thus, the likelihood of resight- 3 perching male and a female engaging in this behaviour. In all ing a captured male was not predictable on the basis of any of cases the female flew fast and directly from the site with the these variables. I calculated territorial site fidelity in the male in pursuit; these chases lasted 10.9 ± 6.4 s (range group of males that were resighted (within 5–10 m of their 6–17 s) and never resulted in copulation. precapture perching location) as the number of days between The only observed interactions involving a receptive first and last sighting. This parameter ranged between two female occurred at 1809 hours on 27 April (ambient light and 23 days (mean = 8.1 ± 9.2 days). level = 200 lux). On this occasion, a fresh WS-form female, flying about 3 m high in a northerly direction along the forest Ambient and male thoracic temperatures edge, was encountered by a territory resident (male A; ‘fresh’ WS form). This male chased the female into the immediate Ambient temperature at the times and places in which males riparian foliage, where the pair was disturbed by a neighbour- were captured ranged from 24.0 to 27.2°C. Captured males ing territory holder (male B). Males A and B then proceeded (n = 29) had thoracic temperatures ranging from 28.2 to to interact amongst themselves for about 10 s in a manner 38.9°C, thus maintaining thoracic excesses ranging from 2.3 reminiscent of a male–female chase (see above). During this to 11.8°C, and averaging 8.25 ± 0.36°C. The manner in time, the female again flew northward along the forest edge which this was achieved was not evident; there was never where she was promptly encountered by another neighbour- any direct sunlight at the site and perching males did not ing male resident (male C; ‘fresh’ DS form). After a very appear to visibly ‘shiver’ in the manner of other crepuscular brief chase (2 s), this pair landed on riparian foliage about butterflies (e.g., Caligo and Opsiphanes: Srygley 1994). Males 4 m high and copulated immediately. that were caught while participating in an aerial ‘diving’ interaction tended to have greater thoracic excesses (mean = 8.90 ± 0.49°C, n = 8) than those caught while perching (mean = 8.01 ± 0.40°C, n = 21). This difference was not sig- DISCUSSION nificant (independent t27 = 1.23, P = 0.23), but the contrast lacked appreciable statistical power (1-β = 0.37). Thoracic Anecdotal reports of the mate-locating behaviour of male excess was also statistically unrelated to forewing length M. leda suggest that individuals defend perching sites in the (Pearson r = 0.19, n = 28, P = 0.34; power = 1-β = 0.47). manner of other territorial butterflies (see Parsons 1999; 304 DJ Kemp

Braby 2000 and references therein). The data presented here territories (Srygley 1994; Freitas et al. 1997; Srygley & Penz confirm this view and provide some interesting additional 1999), but a more formal test is clearly required. insights. The most salient findings are that: (a) males perch Along with visual influences, the relatively cool condi- at, and defend, specific locations along encounter sites that tions and lack of incident solar irradiation are likely to pose a contain larval host-plants and are used by other perching special problem for the mate-locating males of crepuscular male butterflies during the day (see Kemp & Rutowski 2001); species. Most perching butterflies are obliged to maintain (b) males are only present at these sites in the evening and their body temperature within a specific range (usually their appearance is at least partially (negatively) dependent 30–40°C; Rutowski et al. 1994) that is conducive to efficient upon ambient light intensity; (c) site fidelity is generally or optimum flight performance. This is generally achieved by high, ranging up to 23 days; and (d) males maintain a thoracic a mixture of basking and heat avoidance behaviours (e.g., temperature excess up to 11.8°C, in the absence of sunlight Rutowski et al. 1994). Clearly, because crepuscular species and noticeable shivering. Also, the several observed male– cannot use the sun to elevate their temperature, they must female interactions (including one mating) strengthen the employ other thermoregulatory mechanisms or else fly at hypothesis that male Melanitis defend territories specifically lower thoracic temperatures. In a study of the thermal ecology to encounter receptive female conspecifics. of crepuscular brassolines, Srygley (1994) found that individ- In terms of the behavioural classifications of Rutowski uals elevate their body temperature 10–15°C above ambient (1991), the most stark difference between M. leda males and levels by shivering. Territorial male M. leda in this study also other studied species (with the exception of Caligo: Freitas exhibited considerable thermal excesses (ranging up to et al. 1997; Srygley & Penz 1999) is simply with respect to 11.8°C), but the mechanism involved was not evident. Aside the timing of encounter-site occupation. Quantitative aspects from shivering, it is possible that heat generated during flight of male Melanitis behaviour such as site fidelity and thoracic outweighs that lost as a result of convective cooling and that temperature are comparable to that of other territorial nym- there is a net increase in thoracic temperature because of phalids that defend the very same perching sites at other flight itself. The mean thoracic excesses of males captured times of the day (see Kemp & Rutowski 2001; Kemp 2001). either perching or flying seem to suggest this, but unfortu- Qualitatively, male M. leda also appear to have much in nately the associated significance test is ambiguous because common with daytime-active nymphalids (Baker 1972; of the low and unequal sample size (= low statistical power). Rutowski & Gilchrist 1988; Kemp 2001). However, aside Further sampling, incorporating adequate controls for the from the question of why males are only present when they amount of time spent perching or flying prior to capture, are (which is beyond the scope of this paper), a limited would provide a more robust test of this hypothesis. evening residency period does present a special physical Some existing behavioural reports (Common & Water- environment for a mate-locating insect. I now turn to a brief house 1981) suggest that Melanitis are active at both dusk discussion of how this environment may have biased the and dawn, while others (McCubbin 1971; Parsons 1999) hold direction of behavioural evolution in crepuscular species. that these species fly only in the evenings. During my study, From a visual perspective, crepuscular species operate I only sampled once at dawn, but this was at a time when under conditions of severely reduced ambient light intensity: maximum activity was being recorded in the evening cen- the maximum of this study (2600 lux) is at least two orders of suses, and when weather conditions were otherwise fine magnitude lower than it would be during most of the day (the (albeit probably cooler than during the evening). As I did not sunny midday light level at this site is about 1.5 × 105 lux; see a single butterfly, it appears probable that male M. leda D.J. Kemp, unpubl. data, 1998). This means that the bright- search for mates mostly, or exclusively, in the evening. Both ness contrast between a flying butterfly and a terrestrial M. leda and its closely related congener M. amabilis Bois- background, such as foliage, would be greatly diminished in duval are reported to fly only at dusk in Papua New Guinea the evening. Patrolling should be disfavoured at these times (Parsons 1999). Among the relatively more distantly related because greater photon flux is required to detect a given crepuscular butterflies, some are active only at dawn (e.g., stimulus against a moving visual field (Lythgoe 1979). The C. idomenaeus; Freitas et al. 1997), some only at dusk (e.g., best background against which to detect a flying object C. memnon Felder, Catablepia amphirrhoe Hübner, Opsiphanes would be the western sky, which is diffusively illuminated as cassina Felder; Srygley 1994) and some at both times of the a result of Rayleigh-scattered light from the already set sun. day (e.g., C. eurylocus Fruhstorfer; Srygley 1994, C. illioneus Thus, we might expect that males would position themselves and C. oileus; Srygley & Penz 1999). Although ambient light to view flying females as silhouettes against the sky, which levels may span comparable ranges at both dawn and dusk, could favour a stationary tactic. Data presented here are not ambient temperature will differ markedly and will almost adequate to test this hypothesis convincingly, but they do not always be lower in the morning, which may be more con- contradict it, because (a) males perched facing a westerly straining to insect activity. A fruitful avenue for future study direction and (b) the one clearly receptive female flew along might be an investigation into the extent to which thermally the forest edge at a height (about 3 m) where she would be relevant factors, such as body size and endothermic mecha- silhouetted against the sky from the viewpoint of the perch- nisms (Bartholomew 1981; Srygley 1994), can explain dif- ing males. Also supportive is the fact that all other crepus- ferences between the preferred activity schedules of these cular butterflies investigated thus far defend perching crepuscular butterflies. Mate location in Melanitis 305

ACKNOWLEDGEMENTS Kemp DJ. 1998. Oviposition behaviour of post-diapause Hypolimnas bolina (L.) (Lepidoptera: Nymphalidae) in tropical Australia. This work was supported by joint funding from James Cook Australian Journal of Zoology 46, 451–459. and Arizona State Universities. Kemp DJ. 2000. Contest behavior in territorial male butterflies: Does size matter? Behavioral Ecology 11, 591–596. I thank Ronald Rutowski (Arizona State University) for Kemp DJ. 2001. Investigating the correlates of behavioral plasticity in editorial comments and helpful discussion. the territorial butterfly Hypolimnas bolina. Journal of Insect Behavior 14, 129–147. Kemp DJ & Rutowski RL. 2001. Spatial and temporal patterns of territorial mate locating behaviour in Hypolimnas bolina (L.) (Lepi- REFERENCES doptera: Nymphalidae). Journal of Natural History 35, 1399–1411. Lythgoe JN. 1979. The Ecology of Vision. Clarendon Press, Oxford, Alcock J & O’Neill KM. 1986. Density-dependent mating tactics in the UK. grey hairstreak, Strymon melinus (Lepidoptera: Lycaenidae). McCubbin C. 1971. Australian Butterflies. Nelson, Melbourne, Journal of Zoology 209, 105–113. Australia. Andersson M. 1994. Sexual Selection. Princeton University Press, Parsons M. 1999. Butterflies of Papua New Guinea: Their Systematics Princeton, USA. and Biology. Academic Press, London, UK. Baker RR. 1972. Territorial behaviour of the nymphalid butterflies, Ravenscroft NOM. 1994. Environmental influences on mate location in Aglais urticae (L.) and Inachis io (L.). Journal of Ecology male chequered skipper butterflies, Carterocephalus palaemon 41, 453–469. (Lepidoptera: Hesperiidae). Animal Behaviour 47, 1179–1187. Bartholomew GA. 1981. A matter of size: an examination of Rutowski RL. 1991. The evolution of male mate-locating behavior in endothermy in insects and vertebrates. In: Insect Thermoregulation butterflies. American Naturalist 138, 1121–1139. (ed. B Heinrich) pp. 46–78. Wiley, New York, USA. Rutowski RL, Demlong MJ & Leffingwell T. 1994. Behavioural Bateman AJ. 1948. Intra-sexual selection in Drosophila. Heredity 2, thermoregulation at mate encounter sites by male butterflies 349–368. (Asterocampa leilia, Nymphalidae). Animal Behaviour 48, Bitzer RJ & Shaw KC. 1995. Territorial behaviour of the red admiral, 833–841. Vanessa atalanta (Lepidoptera: Nymphalidae) I. The role of Rutowski RL & Gilchrist GW. 1988. Male mate-locating behaviour in climatic factors and early interaction frequency on territorial start the desert hackberry butterfly, Asterocampa leilia (Nymphalidae). time. Journal of Insect Behavior 8, 47–66. Journal of Research on the Lepidoptera 26, 1–12. Braby MF. 2000. Butterflies of Australia: Their Identification, Biology Srygley RB. 1994. Shivering and its cost during reproductive behaviour and Distribution. CSIRO Publishing, Melbourne, Australia. in Neotropical owl butterflies, Caligo and Opsiphanes (Nymphal- Brakefield PM. 1987. Tropical dry and wet season polyphenism in the idae: Brassolinae). Animal Behaviour 47, 23–32. butterfly Melanitis leda (): phenotypic plasticity and Srygley RB & Penz CM. 1999. Lekking in neotropical owl butterflies, climatic correlates. Biological Journal of the Linnean Society 31, Caligo illioneus and C. oileus (Lepidoptera: Brassolinae). Journal 175–191. of Insect Behavior 12, 81–103. Cohen J. 1988. Statistical Power Analysis for the Behavioral Sciences, Trivers RL. 1972. Parental investment and sexual selection. In: Sexual 2nd edn. Lawrence Erlbaum Associates, Hillsdale, New Jersey, Selection and the Descent of Man, 1871–1971 (ed. B Campbell) USA. pp. 136–179. Heinemann, London, UK. Common IFB & Waterhouse DW. 1981. Butterflies of Australia, 2nd Vane-Wright RI & Boppré M. 1993. Visual and chemical signaling in edn. Angus & Robertson, Sydney, Australia. butterflies: functional and phylogenetic perspectives. Philosophical Dennis RLH & Shreeve TG. 1988. Hostplant-habitat structure and the Transactions of the Royal Society of London (B) 340, 197–205. evolution of butterfly mate-locating behaviour. Zoological Journal Wickman P-O. 1985. The influence of temperature on the territorial and of the Linnean Society 94, 301–318. mate locating behaviour of the small heath butterfly, Coenonympha Freitas AVL, Benson WW, Marini-Filho OJ & de Carvalho RM. 1997. pamphilus (L.) (Lepidoptera: Nymphalidae). Behavioral Ecology Territoriality by the dawn’s early light: the neotropical owl and Sociobiology 16, 233–238. butterfly Caligo idomenaeus (Nymphalidae: Brassolinae). Journal Wickman P-O & Rutowski RL. 1999. The evolution of mating of Research on the Lepidoptera 34, 14–20. dispersion in insects. Oikos 84, 463–472. Jiggins FM, Hurst GDD & Majerus MEN. 2000. Sex-ratio-distorting Wolbachia causes sex role reversal in its butterfly host. Proceedings of the Royal Society of London (B) 267, 69–73. Accepted for publication 8 May 2002.