Some notes on oriental dragonflies: the genus Macromia
F.F. Laidlaw’s 1922 monograph on the Oriental genus Macromia provides a systematic revision of the dragonfly genus across the Indo-Malayan region, describing three new species and establishing a morphological framework for distinguishing among at least eighteen known species based on genital structures, abdominal coloration, and wing characters.
Summary
Laidlaw undertakes a taxonomic revision of Macromia in the Orient, a genus of large, strong-flying dragonflies that he notes are difficult to capture and “will repay careful study in the field” (p. 219). His primary diagnostic criteria are the shape of the anal appendages and genital structures of the male’s second abdominal segment, the size of the pterostigma, the presence or absence of metallic lustre on abdominal segments 2–6, and the form of the dorsal process on the tenth segment. He organizes the species into three principal groups: the M. westwoodi group (metallic-lustre abdomen, small pterostigma), the M. cincta group (non-metallic abdomen, larger pterostigma, confined to Malaya and Indo-China), and the M. calliope group (defined by Ris, with a black thorax bearing a humeral band and no dorsal process on segment 10).
The paper’s principal contribution is the description of three new species—M. cydippe from Borneo, M. corycia from Borneo, and M. callisto from the Malay Peninsula—each distinguished from its nearest allies by subtle differences in genital hamule shape, anal appendage proportions, and abdominal markings. Laidlaw also re-examines M. westwoodi, arguing that the male previously attributed to it by de Selys and Kruger actually belongs to a different species, and he identifies a curious structural thickening on the ventral margin of the tenth tergite in the cincta group that may be functionally connected to the genitalia (pp. 224–225). His material derives largely from the Raffles Museum, Singapore, and the British Museum, supplemented by specimens from Tonkin, the Khasi Hills, and India.
Key Findings
- At least eighteen species of Macromia are recognized from the Orient, with the number expected to increase considerably (p. 219).
- Three new species are described: M. cydippe (♂ hind-wing 40 mm, Borneo), M. corycia (♂ hind-wing 34 mm, Borneo), and M. callisto (♂ hind-wing 31.5 mm, Malay Peninsula—the smallest Oriental species of the genus) (pp. 219–226).
- The M. cincta group is characterized by a pterostigma of approximately 3 mm, non-metallic abdominal segments 2–6, and a unique thickening of the ventral margin of the tenth tergite bearing stiff short hairs, a feature not observed in other Oriental groups (pp. 220, 224–225).
- M. callisto is distinguished from the similar M. gerstaeckeri Kruger by the complete absence of a dorsal process on the tenth segment, a smaller overall size, and a straighter anal margin of the hind-wing (p. 225).
- Bornean species are listed as M. cincta (forma), M. cydippe, M. corycia, M. euterpe, with M. borneensis, M. westwoodi, and M. gerstaeckeri included with some doubt; the Malay Peninsula yields only M. westwoodi and M. callisto (p. 228).
- Kennedy (1915) was compelled to use a shotgun to obtain his first specimens of the American M. magnifica, illustrating the difficulty of capturing these insects (p. 219).
Conclusion
Laidlaw establishes that the Oriental Macromia fauna is considerably more diverse than previously recognized, with three distinct morphological groups separable by a combination of genital, coloration, and wing characters. His revision corrects earlier misidentifications—particularly the conflation of M. westwoodi males with allied species—and provides a practical framework for future field workers, while flagging several species (M. borneensis, M. fumata, M. septima) that remain insufficiently characterized and will require further study.
Context
- Primary material drawn from the Raffles Museum, Singapore, and the British Museum, with additional specimens from Tonkin, the Khasi Hills, and India.
- The paper builds directly on Ris (1916) and Martin (1906), and Laidlaw’s own earlier descriptions in the Proceedings of the Zoological Society of London (1902, 1915, 1920), representing a cumulative revision of the genus across the Straits Settlements and Borneo.