Genus

Genus : Gynacantha

Gynacantha is a genus of mainly large species found throughout the world's tropics. Seven species are found in Borneo, one endemic.

The males are generally recognized by the very swollen, almost spherical base to the abdomen with large rounded ear-like auricles on segment 2 followed by an extremely constricted third segment and long, thin, simple superior appendages. The base of the abdomen is often very colorful with bright green flecks on the dorsum and bright blue auricles, but some species are more somberly colored. The easiest way to separate both males and females from the sometimes similar Heliaeschna is by the lack of any cross veins in the median space at the base of the wing ..

Female Gynacantha are difficult to identify to species. They are typically a little larger in wingspan than the males and have extremely long anal appendages. These however are seldom intact and apparently always break off during mating. The third abdominal segment is distinctly constricted, though less so than in the males.

Gynacantha species are found from lowland swamp forest to about 1000 m in the case of basiguttata, bayadera and dohrni.

Typically they are seen hawking at dawn or just before and after dusk and in these situations it is quite common to see virgin females with intact appendages which in flight appear very like males.

Gynacantha species become active in the evening and often come to artificial light.

This is the third Gynacantha basiguttata in 2007 visited our sitting room in early evening. Gemok Hill is 2 kilometers away, that hill could be the habitat from where they came from.

More about Gemok Hill of Sabah...

Males of basiguttata and dohrni guard these pools, or if the pool is large, several males may share it, each defending a well defined territory. They perch conspicuously on emergent twigs with the abdomen hanging vertically in the manner typical of all aeshnids. Females arriving are normally mated before they are allowed to oviposit, inserting their eggs into dead leaves and twigs.

During the day they are found resting in deep undergrowth or in overhangs at the head of small gullies, but from noon onwards they may be reproductively active around shallow leaf-bottomed pools in deep forest shade.

Photo Left : This is a matured female with long anal appendages which is un intact half broken.

The larvae are typically aeshnid in general form, but are easily separated from other genera by the presence of long fine bristles on the labial palps. They are found in leafy forest pools but may be difficult to discover among deep layers of litter.

Gynacantha dohrni is the commonest species and is a moderately large insect (hw, 43-45 mm), brightly colored in life. The pale, narrowly triangular, inferior anal appendage is less than one third the length of the long thin superiors, which are very slightly distally expanded with a small hook at the tip.

Gynacantha demeter is very similar to Gynacantha dohrni in size and structure. Gynacantha demeter is endemic.

Gynacantha subinterrupta is widespread through Sabah but uncommon to see one.

Gynacantha maclachlani is slightly larger from north and west Borneo. All differ from one another in slight details of the male appendages and the coloration of the thorax and are quite difficult to separate.

Gynacantha basiguttata. is the most common species of Sabah. It is larger than G. dohrni and the male superior appendage is expanded into a distinct spatulate shape with a concentrated tuft of hairs at its tip. The inferior appendage is almost half as long as the superiors.

(hw, 45-47 mm)

Photo Left : A female Gynacantha basiguttata (captured and released)

Gynacantha limbalis ( hw, 61 mm) is the largest Bornean species. But this species has not been seen in Sabah yet. The superior appendages are quite straight and narrow as in dohrni but the inferior is between one third and half the length of the superiors. Also there is a distinctive brown streak along the leading edge of both wings. It might be mistaken for a Tetracanthagyna species but for the basally swollen abdomen constricted at the third segment. In Borneo it has been recorded only from Sarawak.

Gynacantha bayadera is fairly common and ubiquitous species, and easily the smallest member of the genus ( hw, 37-41 mm). It is immediately recognized by the basal segments of the abdomen which are only slightly swollen, the auricles which are triangular instead of semicircular, the less pronounced constriction of the third segment and the fairly short, absolutely straight superior appendages. The hind wing is relatively broad, being as wide as in the considerably larger Gynacantha dohrni.