Reproductive Behaviour of Chlorocyphidae. Part 1. Genus Sclerocypha Fraser, 1949 (Odonata)

Reproductive behaviour of genus Sclerocypha 1st December 2019285

Reproductive behaviour of Chlorocyphidae. Part 1. Genus Sclerocypha Fraser, 1949 (Odonata)

André Günther

Naturschutzinstitut Freiberg, B.-Kellermann-Str. 20, 09599 Freiberg, Germany;

Received 25th September 2019; revised and accepted 10th October 2019

Abstract. The reproductive behaviour of the damselfly Sclerocypha bisignata (Chlorocyphi- dae) was studied in various fast flowing streams in mountainous regions of Central Sulawesi. Using high speed cinematography males were shown to exhibit protracted threatening flights with a stationary display of the fore wings. In steady threatening flight the abdomen was held horizontally and the stroking of the hind wings paused briefly and regularly every 2−5 wing beats. These flights were interrupted periodically by short bursts of increased intensity were males arched their abdomens upwards and the hind wing beat was continuous. This flight style differs in several respects from any chlorocyphid species yet studied. During courtship the males presented all three pairs of legs; as courtship intensified they briefly raised their abdomen and presented stationary fore wings. Oviposition took place with the female completely submerged. Unlike most Chlorocyphidae, oviposition sites and male display sites were well separated and ovipositing females were unguarded. Further key words. Zygoptera, Sclerocypha bisignata, Libellago, threat display, courtship, stationary wing display, mating systems, Sulawesi

Introduction The Indonesian island of Sulawesi hosts an extraordinarily rich fauna of the family Chlorocyphidae (Ris 1916; Fraser 1949; van Tol 1998, 2007; van Tol & Günther 2018). Three monotypic, endemic genera are known from the island: Disparocypha Ris, 1916, Sclerocypha Fraser, 1949, and Watuwila van Tol, 1998. Very little has been published on the biology and ecology of the three species of these genera. The present paper describes for the first time the behaviour of Sclerocypha bisignata (McLachlan, 1870), based on field studies in Central Sulawesi. It forms the first in a series of reports on the behaviour and ecology of various Chlorocyphidae in the Australasian, Indo-Malayan and Afrotropical regions. In many chlorocyphid species males defend small territories around high quality oviposition sites, monopolizing this resource (e.g., Robertson 1982;

Odonatologica 48(3/4) 2019: 285-304Odonatologica – DOI:10.5281/zenodo.3539742 48(3/4) 2019: 285-304 286 A. Günther

Orr 1996). This is the primary basis for a general pattern of reproductive behaviour which gives rise to a variety of mating systems. These systems are influenced by the population density of the species and the temporal stabil- ity of the habitats and resources (Günther 2008). Species recognition seems to be primarily based on visual signals (e.g., Robertson 1982; Orr 1996; Günther 2008; Karjalainen & Hämäläinen 2013). Males of most species are brightly coloured and richly ornamented either on the body or the wings or on both (Orr 1996). They exhibit highly complex and ritualized, species specific threat and courtship behaviour. Several studies have shown that there is a close connection between the colouration of the body, wings and legs and their presentation in threatening flights as well as in courtship display (e.g., Robertson 1982; Rudolph 1993; Orr 1996, 2009; Telford et al. 1996; Günther 2008). Studies in tropical Southeast Asia and New Guin- ea of coloured-winged chlorocyphids (Orr 1996; Günther 2008) revealed highly specialized flight patterns associated with the presentation of their coloured wings, including stationary presentation of wings, pauses in wing beating, simultaneously presenting the under surface of all wings, or alternating wing beat rate with bursts of intensified frequency. As summarized by Orr (1996), the agonistic and courtship displays of Chlorocyphidae »include both morphological and behavioural components: i.e., ornaments per se and the actions which reveal them«. The possible evolutionary origins of wing ornamentation and displays are suggested by the clear-winged African chlorocyphid Chlorocypha cancellata (Selys, 1879). Males of this species exhibit context and behaviour dependent changes in the wing beat frequency, suggesting that chlorocyphid species with clear wings can use specialized flight modes for intraspecific signallingGünther ( 2015). In contrast to the males, the females are usually cryptically coloured and behave very incon- spicuously. In most species the females have unmarked, hyaline wings. Ovi- position generally takes place in dead plant material near the water surface, but the range of oviposition sites varies from fully submerged up to high over the water on mossy logs and dead wood (e.g., Orr 1996; Günther 2008). Group oviposition is common (e.g., Martens & Rehfeldt 1989; Orr 2009). Sclerocypha bisignata is a large chlorocyphid with long, slender and mostly hyaline wings (Fig. 1). In the males the tips of the fore wings have opaque markings, as in many Libellago species, with some blue iridescence visible at

Odonatologica 48(3/4) 2019: 285-304 Reproductive behaviour of genus Sclerocypha 287 certain viewing angles. The fore wing of the male has no pterostigma. The costa of the fore wing is thickened and coloured red over about three cells anterior to the nodus. Proximal to the nodus the fore wings have a trans- verse opaque to semi-opaque brownish black patch, with blue reflections in the opaque areas. The hind wings are without these dark markings but in older males, both pairs of wings develop a light brownish tint. In the males the thorax is generally black with yellow and orange markings and the abdomen is predominantly red. The legs are black with extensive white markings on the inner sides of tibiae and femora. Sclerocypha females are inconspicu- ously coloured and without wing markings. The species was described as Micromerus bisignatus by McLachlan (1870) and later placed by Fraser in the monotypic genus Sclerocypha Fra- ser, 1949. Van Tol (2007) revised Sclerocypha together with the probably closely related Sulawesian species of the genus Libellago Selys, 1840, but re- tained its status as a separate genus. Sclerocypha bisignata is endemic to Sulawesi and has been found mainly »in the mountains of Central Sulawesi, southwards to the Latimojong area« (van Tol 2007). Furthermore van Tol (2007) notes: »One 19th century

Figure 1. Sclerocypha bisignata, male. Stream Sg. Torau northwest of Danau Poso, Sulawesi Tengah, Indonesia. Photo: AG (08-xii-2018)

Odonatologica 48(3/4) 2019: 285-304 288 A. Günther record from the Togian islands. Remarkably, the type was collected near Tondano in the eastern tip of the northern peninsula. Only one other specimen is known from the northern arm of Sulawesi, from exactly the same lo- cality. Collecting in this area by Coomans de Ruiter, a collector of many un- common species of Odonata, never revealed another specimen«. Searches for the species in the Tondano area by Jan van Tol in January 1989 (van Tol 2007 and pers. comm.) and by me in August 2011 as well as on the Togian islands in 1994 and 1999 by me were all unsuccessful. Some additional and more recent records from Central Sulawesi were published by Günther (2008), Hoess (2014) and Benstead (2017).

Material and methods Study area The main study area was the mountainous area northwest of Danau Poso. During the 1990s, the area along the road to Gintu (west of Danau Poso) was

Figure 2. Stream Sg. Torau, Sulawesi Tengah, Indonesia. Habitat of Sclerocypha bisignata, Disparocypha biedermanni and Rhinocypha phantasma. Photo: AG (09- -xii-2018)

Odonatologica 48(3/4) 2019: 285-304 Reproductive behaviour of genus Sclerocypha 289 still largely covered by more or less virgin forest. In 2018, large parts of the area were designated as a settlement area. Deforestation took place especially in the vicinity of the streams, now dominated by clearings and plantations. Most observations were made at Sungai (Sg.) Torau just above the road from Tentena to Gintu (1.791861°S, 120.504306°E; 1 029 m a.s.l., Fig. 2). This fast flowing, steep stream averaged about 3–4 m in width but frequent- ly divided into two to three streamlets. The substrate was stony with many large stones and rocks. The water was clear without dystrophic brown tinting. Vegetation was mostly absent in the stream except for some mosses, ferns and seedlings on large emergent stones. The banks in the study section supported disturbed primary forest. The source of the stream is in forest but there was a small, recently cleared area upstream of the observation point.

Methods Reproductive behaviour was observed and filmed from 08–12-xii-2018 at Sg. Torau. Further behavioural observations were made on March 1993 and July/August 1994 (see Table 1). Latitude and longitude coordinates are given in decimal degrees (WGS84) and were taken with a handheld GPS device Garmin Oregon 450t (2018) or derived from Google EarthTM (1993/94). The water temperatures were measured with a digital thermometer, the pH with Czensny indicator. Behaviour was monitored from the morning when the males arrived at their territories, until afternoon when reproductive activity ceased. On most observation days this was about 15:00 h solar time as sunlight disappeared from the stream section. Analysis of behaviour was assisted by extensive video footage. I used a Casio EX-F1 camera (Casio Computer Co., Japan) to record S. bisignata in flight at 600 f/s with sufficient resolution for single- frame analysis. For methodological details see Günther et al. (2014). The recordings were analysed with QuickTime Player version 7.7.8 (Ap- ple, Inc., USA). To obtain the wing beat frequencies I counted sequential frames separated into down stroke, up stroke and wing beat pauses. To min- imize errors some problematic recordings were analysed at least twice. In order to calculate the wing beat frequency the exposure rate (number of frames per second) was divided by the number of frames per wing beat. Wing stroke angles (i.e., the angle described by the wing in a single beat)

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Table 1. Observational sites of Sclerocypha bisignata in Central Sulawesi – Jalan: road, Sungai: river.

Observation site Coordinates Elevation Water tem- Date ♂ per [m a.s.l.], perature, pH 100 m width of stream stream section Besoa, stream 1.633065°S, 1 500 17°C 11-iii-1993 <5 between Rano 120.135037°E Rano and Doda Kamarora, 1.197196°S, 700–800 19°C 16-iii-1993 <5 stream at PHPA- 120.135408°E Camp Kamarora: 1.202365°S, 770–850 18°C 17-iii-1993 <5 stream east of 120.142644°E PHPACamp Jalan Gintu- 1.863718°S, 1 150–1 250, 19°C, pH 6.5 31-vii-1994 <10 Tentena, streams 120.317387°E 5 m 1st mountain pass east of Bomba Jalan Gintu- 1.822431°S, 1 150–1 300, 18°C, pH 6.5 01-viii-1994 >30 Tentena, Sungai 120.362351°E 20–30 m Malei and tribu- tary streams Jalan Gintu- 1.810250°S, 1 650–1 700, 17°C, pH 6.5 02-viii-1994 ca 10 Tentena, Sungai 120.389806°E 5–10 m Boro besar Jalan Gintu- 1.804407°S, 1 750, 16°C, pH 6.0 05-viii-1994 ca 10 Tentena, Sungai 120.436407°E 5–8 m Puna besar street Gintu- 1.797420°S, 1 100–1 250, 17°C, pH 7.0 05-viii-1994 ca 20 Tentena, Sungai 120.493788°E 8–10 m 08-xii-2018 <5 Peatua street Gintu- 1.791861°S, 1 029, 18°C, pH 7.0 08−12-xii- ca 10 Tentena, Sungai 120.504306°E 3–4 m 2018 Torau were estimated to 10 degrees accuracy. Where possible, footage was used in which the damselflies’ flight path and sagittal plane were approximately orthogonal to the direction of recording.

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To analyse the wing beat data I used STATGRAPHICS Centurion XVIII, Version 18.1.12 (StatPoint Technologies, Inc., Warrenton, VA, USA). After confirming the data was non-normal, the nonparametric Mann-Whitney (Wilcoxon) W-test was used to compare the data associated with the different flight types. The Kruskal-Wallis-Test was used to compare the different categories of behaviour.

Results Habitat Sclerocypha bisignata inhabited various fast flowing streams and headwaters of small rivers in mountainous regions from 1 000 to 1 700 m a.s.l. (Table 1). The lowest sites located were at 700 m a.s.l. near Kamarora. The streams ranged from 1 m to 30 m in width. All had a rocky substrate with many large stones and at least partially sunny sections. The water was clear but in some cases (e.g., Sg. Malei, Sg. Boro besar, Sg. Puna besar) had distinctive dystrophic brown tinting. The catchment areas of the streams with S. bisignata were always in forest and the species was absent from muddy and polluted watercourses; e.g., if paddy fields had affected the water quality. As far as measurements are available, the pH varied between 6.0 and 7.0 and the water temperature between 16°C and 19°C. In 1994, along the road from Ten- tena to Gintu, S. bisignata was found at all sampled cold mountain streams above 1 000 m a.s.l., with the exception of Sg. Boro kecil (pH 5.0) and Sg. Leo (pH 4.5), both of which arose in a boggy plateau. The majority of habitats were small creeks and streams in which the species only reached low population densities of less than 5–10 males per 100 m stream section (Table 1, Fig. 2). Males were usually found along small sunny sections, even at small cleared areas next to roads and open country. At higher altitudes the preference for forests seemed to decrease. In 1994, S. bisignata was found on Sg. Boro besar (Fig. 3) with more than 10 males per 100 m of stream section, and on Sg. Malei (Fig. 4) with more than 30 males over the same distance. At that time, both rivers were still nearly unaffected by clearing. At Sg. Torau S. bisignata, Rhinocypha phantasma Lieftinck, 1935, and Disparocypha biedermanni Ris, 1916, occurred syntopically on the same section. In all other localities S. bisignata was the only chlorocyphid present.

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General behaviour Adult males arrived in the morning at the water when the first flecks of sunlight were visible on the stream; on cloudy mornings they waited until the sun came out. Even on clear mornings, due to the heavy shade at Sg. Torau, the first males did not arrive at the water until 09:30 h solar time. They perched near fast flowing water on large stones and emergent dead wood or at 1–3 m in fringing vegetation. With the exception of their display flights they mostly flew rapidly and unpredictably and were difficult to track by eye. At low population densities males established territories of 2–4 m diameter around their perches, but with the appearance of other males, territoriality broke down. Males then perched almost side by side on the same stones. This occurred on all observation days. During these periods the longest-lasting threatening flights were observed. The perches were only used as far as the small stream section was in full sunlight. Therefore, most males shifted their perches throughout the day.

Figure 3. Stream Sg. Boro besar, Sulawesi Tengah, In- donesia. In 1994 the stream was still in undisturbed mountain rain forest and Sclerocypha bisignata was found with more than 10 males per 100 m stream section. Photo: AG (03-viii- -1994)

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Without direct sunshine the males disappeared within a few minutes into the higher surrounding vegetation and later into the forest. Generally on days without sunshine no S. bisignata were observed. From about 11:00 h solar time females approached, perching in the bank vegetation ca 1–3 m above the water surface. Courtship (n = 8) and copula- tions (n = 3) were observed at those sites. In all observed cases (n = 7), oviposition took place with the female submerged near the bottom of the stream up to 50 cm underwater. On all days of filming, reproductive behaviour fin- ished prematurely between 13:30–15:00 h solar time due to afternoon cloud.

Male–male interactions Males exhibited characteristic behaviour towards conspecifics of their own sex. As soon as several males were present on the stream, they started protracted threatening flights. Contests began when one male flew into another’s territory (in the case of low densities with single occupant territoriality)

Figure 4. Stream Sg. Malei, Sulawesi Tengah, Indonesia. In 1994 Sg. Malei was still unaffected by large clearings. The population density of Sclerocypha bisignata was higher than 30 males per 100 m stream section. Photo: AG (01-viii-1994)

Odonatologica 48(3/4) 2019: 285-304 294 A. Günther or when a male flew towards another male. In many cases, a flying male adopted a hovering threat display for several seconds in front of a perching male before the mutual threatening flight began. Threatening flights between two males sometimes continued for hours from the forenoon until early afternoon. Nevertheless after long or short bouts of fighting males had short breaks in which the rivals either perched next to one another on the same stone or returned to their preferred perches. Due to the cloudy weath- er such pauses were often triggered by the appearance of clouds blocking the sun. During contests between neighbours no winners and losers could be identified. Physical contact was avoided during aggressive interactions. Oc- casionally, three or more males were involved in threatening flights. These lasted only a few seconds or minutes. The basic pattern of the threatening flights was that two males faced each other head to head at a distance of about 4–6 cm. The terminally pigmented fore wings were raised vertically and held motionless, thrust slightly forward, and canted so as to present the full under surface to the opponent; each male was thus supported entirely by the beating of his hind wings. Legs were not displayed. At irregular intervals, one male would fly closer to the other, causing the other to switch his flight direction, evidently to avoid the nearness with his rival without giving ground, or on other oc- casions one male switched direction in an apparent attempt to elude the other. Both cases usually led to the two changing sides. Then the threat flight was continued slightly lower over the water surface. After a short time both males again reached their previous height above the water. Strong ascending flights by the pair were never observed during contests. The steady threatening flight was interrupted by short periods of increased intensity. These are here termed escalated displays. The analysis of the high- speed footage revealed two different threatening flight modes that were also clearly visible to the naked eye. (1) Non-escalated threat display: This was the most common flight mode in threatening flights. Exact proportions could not be determined, but it was estimated that this flight mode occupied more than 95 % of threatening activity. In this flight mode, as described above, the abdomen was held horizontally and the fore wings were presented nearly motionless at a mutual angle of about 100°, thrust slightly forward, and canted to face the opponent

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(Figs 5a, b, 6). Flight was maintained entirely by the hind wings. The display was characterized by hind wing stroking with pauses. After 2–5 wing beats the hind wings paused after the down-stroke for about 0.02–0.04 s (n = 30). At first the wing beat stopped at an angle of 5° to the abdomen, and then the wings were closed over the abdomen. During these pauses the male lost 3–5 mm height. The mean value of the beat frequency excluding pauses was 35.9 ± 4.8 Hz (n = 20, Fig. 7). (2) Escalated threat display: The steady threatening flights were interrupted several times by short periods of increased intensity. Both males arched their abdomens upwards and the hind wing beat was continuous, without pauses, with a beat frequency of 34.7 ± 2.6 Hz (n = 20, Fig. 5c). However, the difference in beat frequency to the threat flight described above was not significant. During escalated threatening flights, the activity space increased and the fighting males repeatedly changed their position. During short aerial pauses of the threat display, the males hovered with an alternating wing beat employing both pairs of wings (Fig. 5d). The mean beat frequency of hind wings in that flight mode was 25.3 ± 2.0 Hz (n = 20, Fig. 7) and significant lower than in non-escalated (Mann–Whitney (Wilcoxon) W-test: W = 1.5, p <0.001) and escalated threat display (W = 0, p <0.001).

Male–female interactions and female behaviour Since females were only at the stream for a short time each day, courtship behaviour was rarely observed. Male courtship behaviour was triggered by females arriving at the stream and perching in the bank vegetation. During the observation period no mating within territories or at preferred perches of males was observed. Thus, the location and time of a mating were unpre- dictable. When a male discovered a female he usually flew in front of her, circling in a courtship display with wide-spread legs, showing the white- coloured inner faces of the tibiae and femora of all three pairs of legs (n = 8, Fig. 8). In the final phase of courtship before copulation, he arched up his red abdomen and briefly presented the fore wings, held stationary and canted so that the underside faced the female. In all cases observed courtship only lasted a few seconds and unfortunately was not filmed. Matings lasted between one and two minutes (n = 3, duration estimated). Shortly after mating, females disappeared from the observation site. After copulation, males

Odonatologica 48(3/4) 2019: 285-304 296 A. Günther first sat close to the females. As soon as the females departed, the males returned to their preferred perches in the stream. No guiding behaviour by the males was ever observed either before or after copulation. Unreceptive females refused courting males by raising their wings and wing stroking (n = 5). If courtship was not successful, males also perched in the bank vegetation. Usually a male repeated the courtship display 2–5

Figure 5. Sequential pattern of wing beat stroke amplitudes ofSclerocypha bisignata during different flight styles (from left to right). Fore wings: unbroken lines, hind wings: broken lines. Lines going downwards to right – down-strokes; lines going upwards to right – up-strokes. Horizontal lines indicate the wings were held stationary or nearly so. The greater the amplitude of these lines the wider the stroke angles. Abscissa indicates time in seconds. a, b − Non-escalated threat display between two males mainly with pauses in stroking hind wings: Fore wings were presented nearly motionless. c − Escalated threat display between two males with raised abdomen and uninterrupted stroking hind wings fore wings presented motionless. d − Male hovering in a short break of threat display: Counter stroking wing beat with slightly leading hind wings. e − Courtship display of a male toward a flying female: Counter stroking wing beat with reduced stroke angles of the hind wings.

Odonatologica 48(3/4) 2019: 285-304 Reproductive behaviour of genus Sclerocypha 297 times at short intervals (taken together as one event in the count). If a courtship was unsuccessful, the male returned quickly to his perch in the stream, even if the female was still present. In the early afternoon, females were observed searching for oviposition sites. With a slowly counter stroking flight, they approached large stones and emergent dead wood in fast flowing water. The mean beat frequency of the hind wings in that flight mode was 28.9 ± 2.3 Hz (n = 20, Fig. 7) and significant lower than the frequency of male non-escalated (Mann–Whitney (Wil- coxon) W-test: W = 26.5, p <0.001) and escalated threat display (W = 8.0, p <0.001). The difference in beat frequency to the hover flight of males was not significant. If a male saw a female flying close to the water, he again -en gaged in courtship behaviour. The males presented their splayed legs but did not bend the abdomen. During this courtship display males showed a regular counter-stroking wing beat without any pauses but both hind wings

Figure 6. Sclerocypha bisignata, two males in threat display with motionless presentation of the fore wings. Stream Sg. Torau northwest of Danau Poso, Sulawesi Tengah, Indonesia. Photo: AG (08-xii-2018)

Odonatologica 48(3/4) 2019: 285-304 298 A. Günther were stroked at as little as half a full wing beat amplitude (Fig. 5e). The mean beat frequency of hind wings was 31.1 ± 2.9 Hz (n = 11, Fig. 7). There was a significant difference in wing beat frequency compared to male hover flight (Mann–Whitney (Wilcoxon) W-test: W = 348.5, p <0.001) but no significant difference to either of the threatening flight modes and the flight mode of the female during the same action. No successful courtship was observed in these cases. When the females were not harassed by males, they landed near the wa- terline. Then they crawled on stones or dead wood under water down to the bottom of the stream. Obviously oviposition took place under stones and dead wood at or near to the stream bottom but was never observed directly as the females disappeared under these objects. The depth to which they descended ranged from 20–50 cm. On no occasion was the female observed emerging from the water, so no information is available on the duration of uninterrupted oviposition and possible respiratory breaks.

Figure 7. Stroke frequencies of Sclerocypha bisignata for different flight styles. Male non-escalated threat display (n = 20), male escalated threat display (n = 20), male hovering flight (n = 20), male courtship display toward a flying female, female flight in finding an oviposition site. Bars include 50 % of each data set, verti- cal lines in the bars show the median, the horizontal lines with small terminal crossbars show the range.

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Discussion Sclerocypha bisignata is the characteristic chlorocyphid of montane rainfor- ests above 1 000 m a.s.l. in Central Sulawesi. The lowest localities among my own records were two streams at 700 m a.s.l. near Kamarora. These streams flowed down from the mountain rainforest and had a very steep gradient. Van Tol (2007) summarizes the habitat preferences based on museum collection data and his own records as »sunny streams of 2−6 m wide, in mountainous regions between ca 800 and 1 200 m, where Libellago species of the rufescens-group of Sulawesi do not occur«. I found the species at an altitude of 1 700−1 750 m a.s.l. (Sg. Boro besar, Sg. Puna besar, altitude information according to Google EarthTM). In the mountains between Danau Poso and Bada Valley S. bisignata also occurred on the larger streams such as Sg. Malei with a breadth up to 30 m. It has never been found syntopically with Libellago celebensis van Tol, 2007, or other members of the L. rufescens- group sensu van Tol (2007). These species seem to exclude each other due to their habitat requirements and possibly also by interspecific competition. In December 2018 I found a male of Rhinocypha phantasma and three males and two females of Disparocypha biedermanni syntopically with S. bisignata on the stream Sg. Torau. This is the only case I know that S. bisignata was found together with other chlorocyphids on the same section of a stream. However there has been very little fieldwork in Central Sulawesi. Perhaps there exist transitional zones on some streams where all three species occur. Moreover, it cannot be ruled out that the presence of these other species was a result of deforestation along the stream. At larger streams S. bisignata occurred together with the calopterygid Neurobasis kaupi Brauer, 1867 (cf. Günther 2006). The monotypic genus Sclerocypha is probably closely related to Libella go. The reproductive behaviour of the species also indicates this relationship. The stationary presentation of the terminally pigmented fore wings in threatening display flights is so far known to be an exclusive character of the genus Libellago (Orr 1996, 2009; Günther 2008 and unpubl.). This behaviour was termed ‘stationary wing display’ by Orr (1996) and has so far been found in all Libellago species studied with terminally pigmented fore wings. It is absent in species such as L. hyalina in which both wings are unpigment- ed (Orr 1996). For this behavioural trait, homologous development is likely

Odonatologica 48(3/4) 2019: 285-304 300 A. Günther because important homology criteria sensu Tembrock (1992) are met. This relates to the unique colouring of the wings and the style of the presentation in comparison to other Chlorocyphidae and Odonata. This hypothesis supports in particular a close relationship between Sclerocypha and Libel lago and is in agreement with molecular data suggesting a close relationship between Sclerocypha and other Sulawesian red bodied Libellago (Jan van Tol pers. comm.). As with the majority of the Libellago species, all three pairs of legs are presented in courtship display. Representatives of some other Asian genera such as Aristocypha, Heliocypha and Rhinocypha present only the middle and the hind legs towards the female (Günther 2008 and unpubl., shown in Karjalainen & Hämäläinen 2013: 196). However, the presentation of three pairs of legs in courtship occurs in other genera, such as in Sunda cypha (Orr 1999, 2003 and pers. comm.) and in the African genera Chloro cypha, Platycypha and Stenocypha (e.g., Robertson 1982; Rudolph 1993; Günther 2008 and unpubl.). There is also in at least one well documented

Figure 8. Sclerocypha bisignata, male in courtship display in front of a perching female with display of the wide-spread legs, raised abdomen and motionless presentation of the fore wings. The male flies in that moment exclusively with the hind wings.

Odonatologica 48(3/4) 2019: 285-304 Reproductive behaviour of genus Sclerocypha 301 case of secondary loss of dilation and whiteness of all tibiae in Rhinocypha aurofulgens Laidlaw, 1931 (Orr 1996). Therefore presentation of all six legs in display flights may be a primitive character of Chlorocyphidae with the reduction to middle and hind legs derived. However, given the overall pattern of variation in this condition within the family, further study is required to resolve this hypothesis. One feature of escalated threatening flights of S. bisignata was that the males raised their abdomen during the display flight. I found similar behaviour in Libellago rufescens (Selys, 1873) and L. celebensis (Günther 2008) and the behaviour also occurs in many other species of Libellago and other chlorocyphid genera (Orr 1996, 2009; Günther 2015). As with the Libellago rufescens-group, male aggregations sensu Günther (2008) formed part of the mating system. Due to the high population density, the males were unable to occupy and defend territories. The observed matings took place in the bank vegetation far from the sites occupied by males, i.e., well removed from potential male territories. As a result of the separation of oviposition sites and male display sites, neither a presentation of potential oviposition sites nor guiding behaviour to these sites could be observed. However, for a complete understanding of the mating system, the data are still inadequate. My own observations on L. rufescens and L. cele bensis confirm that under low population densities mating systems can change. Territoriality and the associated behaviour with the monopoliza- tion of oviposition sites occur in both species (AG unpubl.). A conspicuous difference to the previously studied species of the L. rufes cens-group was the absence of tandem flights to the oviposition site after mating. This contact guarding behaviour seems to be an exclusive behavioural trait of the L. rufescens-group within the genus Libellago (Günther 2008 and unpubl.). There are also fundamental differences in the oviposition substrates. Both in L. rufescens and L. celebensis, as well as in S. bisignata, oviposition takes place with the females completely submerged. The females of both Libellago species lay their eggs in submerged logs and heavy pieces of driftwood in lowland streams. Such oviposition sites are rare and easy for males to control. This leads to territoriality under low population densities or to male aggregations when that territoriality breaks down at high local population densities. In both cases, males are able to occupy and control at

Odonatologica 48(3/4) 2019: 285-304 302 A. Günther least the most important sites (Günther 2008 and unpubl.). Since only single females arrive at the sites, tandem flight after the mating enables males to ensure the success of that mating and for females to avoid harassment by other males (Günther 2008). In Sclerocypha females crawled under water along stones or dead wood down to the bottom of the stream. Suitable places are very common and widely dispersed along the steep mountain streams and even at high population densities the males cannot fully control potential oviposition sites. In the cases observed, the females were able to reach oviposition sites without concerted harassment by males. Both systems differ greatly from the female aggregations, as described for example for other Libellago species and Heliocypha (e.g., Orr 1996, 2003), Aristo cypha (Günther 2008; Karjalainen & Hämäläinen 2013) or Platycypha (Martens & Rehfeldt 1989). Particularly unusual are the pauses in the stroke of the hind wings in the non-escalated threatening flights, in which the wings are completely closed over the abdomen (Figs 5a, b). From the point of view of flight kinematics, the breaks mean increased energy expenditure. After the break, the wings were moved forward. Thus, there is no aerodynamic positive effect of a ‘clap and fling’ flight as discussed by Wakeling & Ellington (1997) for Calo pteryx splendens. All Libellago species I have filmed in high speed stroke the hind wings continuously in the threatening flights. Changes in wing beat frequency depending on the intensity of the fights occur in most of the species, breaks in the stroke of the hind wings, however, not. Chlorocypha cancellata shows short breaks in stroking of both wing pairs at intervals in escalated threat display (Günther 2015). In this species the males held all their wings still with a stroke angle of about 50–60°. Marden & Waage (1990) defined long lasting threatening flights as ‘energetic wars of attrition’. Most likely, this highly energy-consuming flight mode can be understood as a signal to the rival. However, a dynamic flying style may signal to arriving females as well. Further evidence of a possible semiotic function over greater distance could be the extraordinary morphology of the fore wings with a thickened coastal base with a red marking, the second dark spot with blue iridescence and the very large size of the terminal spot. The reproductive behaviour of S. bisignata is markedly different in several ways from that of most chlorocyphids. Particularly noteworthy are the

Odonatologica 48(3/4) 2019: 285-304 Reproductive behaviour of genus Sclerocypha 303 separation of oviposition sites and male display sites, the occurrence of very protracted threatening flights between males even when territoriality breaks down due to high local population density, and the unguarded oviposition by females. This behaviour suggests that possibly a lek system is in opera- tion. However at present our knowledge of the mating system of S. bisignata is still too limited for this to be more than an hypothesis.

Acknowledgements I wish to thank Albert Orr for his manifold help and support, including a critical reading of the text and stimulating discussions about the behaviour of Chlorocyphidae. The manuscript benefited from helpful comments by Jan van Tol. I am very grateful for the support from PHPA authority in Palu, the local authorities of Lore Lindu National Park and the team of the former Kamarora field station.

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