Chiriquita shadowdamsel  (Palaemnema chiriquita)

This rare damselfly can be recognised by its dark brown to black overall colouring, and the contrasting colour of its thorax, which is shiny green-black at the front and greenish-yellow at the sides. Yellow-tan marks also appear at the start of each segment of the long slender abdomen, giving a distinctive banded appearance. In addition, males have extensive blue colouration on the top of abdominal segments eight and nine, appearing as a blue tip to the abdomen (2) (3).

The Chiriquita shadowdamsel is endemic to Costa Rica, where it is known from just two locations on the Caribbean slope (1).

This damselfly inhabits small streams in lowland rain forest (1). The larvae of Palaemnema are known to live on rocks in small to medium-sized streams (2).

Very little is known about the Chiriquita shadowdamsel's reproductive biology, life history patterns or feeding behaviour. Nevertheless, there are general biological characteristics of dragonflies and damselflies (Odonata) that are likely to apply here. Odonata species start their life as aquatic larvae or nymphs, before passing through a series of developmental stages or ‘stadia' during which they must undergo several moults as they grow (4). The larval period in Palaemnema probably lasts one year (2). Before the final moult (emergence), metamorphosis occurs in which the larvae transform into the adult form. After emergence, adults undergo a pre-reproductive phase known as the maturation period, and this is when individuals normally develop their full adult colour. Odonata usually feed on flying insects, but are generalised, opportunistic feeders, and will often congregate around abundant prey sources such as swarms of termites or near beehives (4).

There is often fierce competition between males for access to reproductive females. Although females typically begin to lay eggs in the water immediately after copulation, often guarded by their mate, they can store live sperm in their body for days (4). In shadowdamsels (Palaemnema), pairs often concentrate at suitable oviposition sites, and males may guard females after copulation to prevent other males from mating with them (2).

The primary threat endangering this rare Costa Rican endemic is widespread deforestation of its lowland forest habitat (1).

The Chiriquita shadowdamsel is found within the Parque Nacional Braulio Carrillo, where it receives some degree of protection. However, there is an urgent need for field surveys to search for other subpopulations and to determine the availability of suitable habitat (forested streams) in the general area (1).

Authenticated (05/07/2006) by Dr. Dennis Paulson, Director Emeritus, Slater Museum of Natural History.
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