Dragonflies of the Golfo Dulce Region, Costa Rica Piedras Blancas National Park “Regenwald der Österreicher” Printed with generous support from the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management 1 Authors Stefan Schneeweihs Department of Population Ecology University of Vienna Rennweg 14, 1030 Vienna, Austria [email protected] Roland Albert Werner Huber Anton Weissenhofer Department of Chemical Ecology Department of Ultrastructure Department of Ultrastructure and Ecosystem Research Research and Palynology Research and Palynology University of Vienna University of Vienna University of Vienna Rennweg 14, 1030, Vienna, Rennweg 14, 1030, Vienna, Rennweg 14, 1030, Vienna, Austria Austria Austria [email protected] [email protected] [email protected] 2 Contents The “Tropical Research Station La Gamba” . 4 The rainforests of the Golfo Dulce region . 6 Introduction . 8 History and diversity of dragonflies . 8 Adults and larvae . 8 Life cycle . 9 Morphology of the adult . 10 Identification . 11 Tropical dragonflies . 11 Odonatological field trips around La Gamba . 12 Forests . 12 Cultivated landscapes . 13 Forest margins . 13 Zygoptera . 14 Polythoridae . 14 Calopterygidae . 16 Megapodagrionidae . 18 Pseudostigmatidae . 20 Protoneuridae . 21 Coenagrionidae . 23 Anisoptera . 28 Gomphidae . 28 Libellulidae . 29 Diversity of dragonflies in La Gamba . 50 Acknowledgements . 50 References . 51 Dragonflies on the web . 51 Picture credits . 52 3 Introduction Visitors to the La Gamba Research ecosystem. Today the order Odonata (drag - Station will find a rich array of tropical life. onflies) is divided into three suborders, the As well as an overwhelming diversity of most common being the smaller Zygoptera plants, they will see birds and butterflies, (also known as damselflies) and the larger two of the most popular and conspicuous Anisoptera. A third suborder, the groups of animals. Hummingbirds, noisy Anisozygoptera, which combines character - toucans, and brilliant butterflies like the iri - istics of the other two groups, is represented descent Morpho or the spectacular Heliconius by two species in Nepal and Japan. are well known throughout the world. But Approximately 5700 species have been there are many other groups which are just described so far, with almost equal numbers as recognisable yet not as widely known. in Zygoptera and Anisoptera. Because larval Unfortunately there is often a dearth of growth responds positively to temperature, knowledge about such organisms, and access dragonflies are assumed to have developed to the relevant literature is difficult. in a warm climate. Today the greatest diver - Sometimes, however, we just need a little sity is found in tropical regions, declining help to find them. Dragonflies are skilled towards higher latitudes. Areas of the high - fliers, fearless predators, and passionate est diversty are found in South America and lovers, and once you notice them, you will South East Asia, especially in montane find them fascinating. regions where examples of previously The ecology and behaviour of the Central unknown species are often reported. American dragonfly fauna has been laid out in detail in the specialist literature (see refer - Adults and larvae ences), and more interested readers are invit - Zygoptera and Anisoptera can be easily ed to consult these sources. This booklet is identified as adults and larvae. Adult designed as a pocket guide to the identifica - Zygoptera are usually finely built insects tion of the most frequently observed species with slender abdomens. The eyes are sepa - around La Gamba. The descriptions of char - rated and situated laterally on the head. acteristics and differences between the Their fore wings and hind wings are fairly species are limited to essential information. similar in shape and venation, and are held Although identification can be difficult, and over the abdomen when resting. In flight for some species beyond the scope of this they are less acrobatic than Anisoptera, and booklet, it should be possible to recognise are often found patrolling in dense vegeta - most of the common species present in the tion near the water’s edge. The larvae of region. For the interested observer, this Zygoptera are small and slender, this shape booklet will serve as an introduction to the often appearing pronounced by the presence diversity of a fascinating group of animals. of three flattened, elongated and highly tra - We hope it will raise awareness of the diver - cheate caudal appendages that serve as res - sity of dragonflies, but also of how urgently piratory organs. Three tropical families form we need to work for their conservation. the exception, showing either lateral gills on the abdomen (Euphaeidae and History and diversity of dragonflies Polythoridae), or gill tufts at the end of the The first fossil records of a group called abdomen (Amphipterygidae). Protodonata, closely resembling today’s Adult Anisoptera are built robustly, with dragonflies and thought to represent their a long or stout abdomen. Their large eyes ancestral form, date from the Upper cover almost the whole head and meet on Carboniferous period 325 million years ago. top of the head, or they can be slightly sepa - With a wingspan of 70 cm, Meganeura monyi rated as in the family Gomphidae. The wings was one of the largest insects ever to have differ in shape and venation and are held lived on the planet. Today’s dragonflies are open when resting. Anisoptera can be considerably smaller, but these ancient observed perching on exposed structures insects still have a valuable place in the along banks, or patrolling for hours over the 8 water surface. The larvae are stout and have ronmental factors like the reflection of the three strong spines instead of lamellate aquatic surface, and the vegetation structure. appendages. They breathe by ‘rectal ventila - After one or more weeks the embryo will tion’, pumping water through the rectum, have completely developed, and the first where a tracheate organ serves for gas larva (prolarva) will be ready to hatch from exchange. Water can be expelled from the the egg. Subsequently, having reached the rectum very forcefully, so that the larva water (in the case of endophytic eggs), the swims forward. This ‘jet propulsion’ is also prolarva starts to moult (i.e. to leave the old used to escape predators. cuticula), in a process called ‘ecdysis’. Larvae and adults are predators and fair - During the larval phase, which can last from ly opportunistic in their choice for prey, a few weeks up to several years, up to 15 although specialisation does occur (see ecdyses are completed, separated by periods Pseudostigmatidae). Both developmental of foraging behaviour and growth. In tem - stages are perfectly adapted to this lifestyle. perate regions, eggs or larvae can display a Larvae actively search out or ambush their diapause, a reduction of metabolism and prey, detecting it visually or by touch, and growth during winter. capture it by the rapid protraction of the The final larval stage, at which an adult modified lower lip (or ‘labium’) which forms is contained within the larval skin, sees the the so-called ‘mask’. Adults detect prey with larva leaving the water for emergence. This their large eyes. In flight, they can turn spectacular scene usually takes place shortly quickly, hover, and even fly backwards, before dawn. The larva climbs up a suitable since the flight muscles insert directly on the structure, often a piece of aquatic vegetation, wing base, allowing them to move each pair and searches for a firm grip with its legs. The of wings independently. Even fast-flying larval skin then bursts at pre-formed points, prey such as other dragonflies can be cap - and the young adult leaves the skin. After a tured by their acrobatic manoeuvres, held by short rest the adult unfolds its wings and their legs, and then manipulated with their abdomen by pumping in haemolymph. After sharp mandibles. emergence, the smooth and shimmering skin first has to harden. Then the dragonfly sets Life cycle off on its maiden flight, leaving the site of Dragonflies are hemimetabolic insects, emergence. exhibiting incomplete metamorphosis and Young adults spend their first days on lacking a pupal stage like that in butterflies; the side of the water in order to build up fat the adult develops during the last larval reserves, and to avoid interference from stage. Their life cycle comprises three phases: mature and territorial dragonflies. The sexu - egg, several larval stages, and adult. The lar - al organs are not yet fully developed, and vae live predominantly in fresh water, inhab - they start to mature during this period. In iting lakes, streams, bogs, and ephemeral some tropical species, when breeding habi - water bodies. Only a handful of species are tats have dried out, this pre-reproductive known to develop in the brackish water of time can be prolonged for months until the marine marshes, or to have terrestrial larvae. beginning of the next wet season. When the Many species are generalists, capable of sexual organs have fully developed, the inhabiting a wide spectrum of freshwater adults turn to suitable water bodies for systems. Some species, however, have nar - reproduction. row breeding site requirements and are thus Males spend many days at reproductive sensitive to disturbances and habitat destruc - sites, where they establish temporary territo - tion. Many of these specialists are rare, but ries that are defended against other males. they can be used for the assessment of eco - Females are often dispersed around other logical freshwater status. habitats and only visit the water bodies for After mating, the female lays fertilised copulation and oviposition. When a female eggs either on the water (exophytic), or into enters a territory, the male flies up and tries (sometimes submerged) plants (endophytic). to grasp her with the caudal appendages, on Before oviposition, suitable habitats for the female’s thorax in the case of Zygoptera, development are selected by the adults.