Spolia mentawiensia. Fulgoroidea. Hornoptera. Introd. C.B. Kloss
F. Muir, working from the Hawaiian Sugar Planters’ Experimental Station in Honolulu, published this taxonomic account of Fulgoroidea (planthoppers) from the Mentawi Islands in 1926, based on material collected during a September–November 1924 expedition led by C. Boden Kloss and H. H. Karny. The paper describes 26 new species from the poorly known island group west of Sumatra, demonstrating a high degree of endemism consistent with the islands’ deep-water isolation from the Sunda shelf.
Summary
This paper forms one instalment of the broader “Spolia Mentawiensia” series documenting the natural history of the Mentawi Islands (Siberut, Sipora, and North and South Pagi), a group lying 90–130 km off the west coast of Sumatra. Kloss’s introduction establishes the biogeographical context: the islands are separated from Sumatra by the Mentawi Basin, with depths of 1000–2000 metres, and are surrounded by water 200–1000 metres deep. This deep-water isolation, Muir argues, renders the islands’ fauna “quite as distinct from each other and from the rest of Malaysia as the larger areas of that sub-region are from each other” (p. 393). The high endemism observed on the nearby Nias Island provided the expectation that the Mentawi group would yield a similarly differentiated fauna, and the results confirm this.
Muir treats 36 species across four families (Cixiidae, Meenoplidae, Delphacidae, and Derbidae), of which 26 are described as new to science, one remains unidentified, and nine are recorded as occurring elsewhere. The new species are all related to other Malaysian taxa, and among the non-endemic records there appears to be a stronger biogeographical connection with Borneo than with any other region, though Muir cautions that the Fulgorids of Sumatra itself are so poorly known that firm conclusions remain impossible (p. 394). The systematic section relies heavily on genital morphology—particularly male genitalia and, where available, female ovipositor structure—as the primary diagnostic character, with 34 figures illustrating these structures.
The collection was made by Kloss, Karny, and N. Smedley with native collectors, working from the government stations at Siberut and Sioban (Sipora), and also from the sea-shore, swamps, cultivated areas, and accessible hills. The expedition of fifteen men suffered near-universal malaria despite quinine prophylaxis, underscoring the difficulty of fieldwork in the archipelago (p. 392).
Key Findings
- Of 36 species treated, 26 are described as new to science, representing a 72% endemism rate for the Mentawi Islands’ Fulgoroidea (p. 394).
- The Mentawi Basin between the islands and Sumatra reaches depths of 1000–2000 metres, and the surrounding sea floor is 200–1000 metres deep, far exceeding the 75-metre threshold of the Sunda shelf (p. 393).
- Siberut Island is approximately 110 km long and 50 km broad, with its northern extremity at 1° South latitude; the other three islands (Sipora, North Pagi, South Pagi) are roughly equal in size and together smaller than Siberut (p. 392).
- The collection was made during September–November 1924 by a party of fifteen, of whom all except Muir contracted malaria (p. 392).
- Among the nine non-endemic species, biogeographical affinities point more strongly toward Borneo than toward Sumatra or other regions (p. 394).
- The genus Ostama was previously known from a single species and single specimen from Borneo; the new O. junctissima extends its range to Sipora, Siberut, and Pulau Tello (pp. 397–398).
Conclusion
Muir’s definitive takeaway is that the Mentawi Islands, despite their modest size and low relief, harbour a Fulgoroid fauna of remarkable distinctiveness, driven by deep-water isolation from the Sunda shelf. The high proportion of endemics validates the biogeographical argument that bathymetric barriers, not merely distance or area, are the primary drivers of faunal differentiation in the West Sumatran island chain.
Context
- The collection was assembled during a 1924 expedition under the auspices of the Raffles Museum, Singapore, and the Zoological Museum at Buitenzorg, with facilities provided by the Government of Netherlands India (p. 392).
- This paper is one of several “Spolia Mentawiensia” contributions (flora, birds, reptiles, and amphibians had already appeared by 1926), representing a coordinated multi-taxa survey of the archipelago’s biodiversity (p. 393).