Some 3,000 species of terrestrial invertebrate have been recorded in Seychelles. The majority of these are known from isolated records or from a small number of specimens. Nature Protection Trust of Seychelles carried out extensive research on the diversity, ecology and conservation of invertebrates in the islands.
NPTS invertebrate research relied upon extensive collections of historical literature and a network of taxonomists providing identification and taxonomic reviews. This enabled the identification of large numbers of species not recorded since the major collection expeditions of 1892-1909 and many new species.
The majority of 'rediscovered' species are small and inconspicuous. One dramatic exception is the Seychelles bee-hawkmoth (Cephonodes tamsi). This species was known from a single specimen from Mahé island in 1911 and was presumed extinct until several individuals were found on Silhouette in 1997. This large, bright red species appears to be locally abundant but very patchily distributed. Since 1997 further dramatic rediscoveries have been made: the Seychelles hummingbird hawkmoth (Macroglossum alluaudi) in 2000 and the Seychelles fineliner damselfly (Teniobasis alluaudi) in 2001.
Fregate island invertebrates
The only conservation measures specifically for invertebrates are the captive breeding programme for the threatened species from Fregate island. NPTS worked with the Zoological Society of London's Invertebrate Conservation Centre to maintain a viable captive population of Seychelles giant millipede (Sechelleptus seychellarum), giant tenebrionid beetle (Pulposipes herculeanus), Fregate island snail (Pachnodus fregatensis) and Seychelles giant scorpion (Chiromachus ochropus). These are all threatened by brown rats (Rattus norvegicus) which invaded the island in 1995. It was feared that rats will feed on these large invertebrates and as the rat population expanded the invertebrates may have become extinct. The millipede is found on several other islands. The beetle is restricted to Fregate island (historically it was also found on Round island near Mauritius and probably on other Seychelles islands) as is the snail. The scorpion is found on other islands in Seychelles but is only abundant on Fregate. All four species are established in captivity, ensuring that a reservoir population is maintained. Rats were eradicated from the island in 2000 and invertebrate population surveys were carried out by NPTS in 2002. Field work on Fregate by NPTS discovered a new genus of snail in 1999, now thought to be Extinct.
NPTS undertook a comprehesive review of all of the terrestrial and freshwater animal biodiversity of the Seychelles islands and produced several scientific publications on taxonomy and conservation, the most important of which are the Seychelles fauna monographs.