Trigoniulus

Trigoniulus Pocock, 1894, is a decent-sized genus of pachybolid millipedes with 60 accepted species as of 2021 (Sierwald & Spelda) that are spread across the Americas, into southeastern Asia, Indonesia and the Pacific islands (iNaturalist, 2021). Members of this genus range in size and color, typically measuring between 60-100mm (2.5"-4.5"). Hoffman & Keeton (1960) state that some authors claim that Spirobolus lumbricinus Gerstacker, 1873, is the type species for the genus, which Hoffman & Keeton argue is synonymous with Spirobolus goesi Porat, 1876, which is named as the orthotype for this genus in their work.

The most common species encountered in captivity is Trigoniulus corallinus, a species native to Southeast Asia into Myanmar and Taiwan, but that has also been introduced into Central and South America, the Caribbean, and most recently into the southern United States with a strong concentration in Florida (Kenny, Shen, Chan, Wong, Fung Chan, Chu, Lam, & Hui, 2015).
T. corallinus was first reported in Florida in South Miami in Miami-Dade County, being collected by Robert M. Carmany and Joseph Burgess under tree bark and in leaf litter. Those discovered and collected were found sympatrically with another introduced spirobolidan, Anadenobolus monilicornis (called Eurhinocricus sp. in the original publication) (Hribar, 2010; Shelley, Carmany, & Burgess, 2006).

Trigoniulus corallinus was the first diplopod species to have its genome sequenced, and only the second Myriapoda species (Kenny et al., 2015).

Trigoniulus macropygus Silvestri, 1897, is also widely kept by hobbyists and is recognized by its contrasting bright, yellow and orange legs, aptly embodying its common name, the flame-leg millipede. Trigoniulus macropygus is native and distributed within the Philippines, with a concentration of siting's in Manila. T. macropygus grows upwards of 4-5"/10.16-12.7cm in length. This species has a relatively short lifespan once reaching adulthood, and may die shortly after maturing and breeding. The species readily consumes soil substrates such as flake soil and humus, as well as fruits like apple, but does not seem to feed readily on leafy vegetables.

Trigoniulus corallinus offspring, photograph courtesy of Vera Miskimen.

Trigoniulus macropygus, photographs courtesy of Kevin Nasser.

References:

  1. Purkart, A. (2021). Trigoniulus corallinus. Trigoniulus Genus Page. Photograph. Permission granted solely to TMED.

  2. Pocock, R. I. (1894). Contributions to our Knowledge of the Arthropod Fauna of the West Indies. Part III. Diplopoda and Malacopoda, with a Supplement on the Arachnida of the Class Pedipalpi. Journal of the Linnean Society of London. 24 (157): 473-519, pl. 37-40., available online at https://biodiversitylibrary.org/page/31652901

  3. Sierwald, P.; Spelda, J. (2021). MilliBase. Trigoniulus Pocock, 1894. Accessed at: https://millibase.org/aphia.php?p=taxdetails&id=892824 on 2022-01-22

  4. iNaturalist. (2021). Trigoniulus. Observations: Map. https://www.inaturalist.org/observations?place_id=any&subview=map&taxon_id=123013

  5. Silvestri, F. (1897). Neue Diplopoden. Abhandlungen und Berichte des Königl. Zoologischen und Anthropologisch-Ethnographischen Museums zu Dresden. 6(9): 1-23. Dresden.

  6. Sierwald, P.; Spelda, J. (2021). MilliBase. Trigoniulus macropygus Silvestri, 1897. Accessed at: http://www.millibase.org/aphia.php?p=taxdetails&id=939215 on 2022-01-22

  7. iNaturaliat. (2021). Trigoniulus macropygus. Map. https://www.inaturalist.org/taxa/888841-Trigoniulus-macropygus

  8. Likhitrakarn, Natdanai, Golovatch, Sergei I., Panha, Somsak (2015): A checklist of the millipedes (Diplopoda) of Cambodia. Zootaxa, 3973 (1): 175-184, DOI: http://dx.doi.org/10.11646/zootaxa.3973.1.7

  9. Golovatch, Sergei I., Wesener, Thomas (2016): A species checklist of the millipedes (Myriapoda, Diplopoda) of India. Zootaxa, 4129 (1): 1-75, DOI: http://doi.org/10.11646/zootaxa.4129.1.1

  10. Nasser, K. (2021). Trigoniulus macropygus. Photographs. Permission granted solely to TMED.

  11. Hribar, J.L. (2010). New Florida Keys Distribution Records for some Arthropods and an Additional Instance of Facultative Carnivory by a Phytophagous True Bug. Florida Scientist, 73(3/4), 259-261. https://www.jstor.org/stable/24321438

  12. Shelley, R.M., Carmany, R.M., & Burgess, J. (2006). Introduction Of The Milliped, Trigoniulus corallinus (Gervais, 1847) (Spirobolida: Trigoniulidae), In Florida, U.S.A. Entomological News, 117(2), 239-241. https://www.researchgate.net/profile/Joseph-Burgess-4/publication/232662384_Introduction_of_the_milliped_Trigoniulus_corallinus_Gervais_1847_Spirobolida_Trigoniulidae_in_Florida_USA/links/55427edd0cf234bdb21a14e4/Introduction-of-the-milliped-Trigoniulus-corallinus-Gervais-1847-Spirobolida-Trigoniulidae-in-Florida-USA.pdf

  13. Flower, S.S. (1901). Notes on the Millipedes, Centipedes, Scorpions, etc., of the Malay Peninsula and Siam. Journal of the Straits Branch of the Royal Asiatic Society, 36, 1-48. https://www.jstor.org/stable/41560967