Orthomorpha coarctata (Long-flange Millipede) is a millipede from the family Paradoxosomatidae presumably native to Southeast Asia. Its length ranged from 16.5 to 27.5 millimetres (mm). Several of them had been roaming around the soil surface of my potted plants for a while now. Recently, I had observed an increase in their population in 2 of the pots. At some instances, there were more than 10 of them congregating together. The young millipedes were light brown in colour.

While the centipedes will inflict painful and poisonous bites, millipedes are generally not harmful creature to human being. Moreover, I found it nice to have some visible creatures crawling among the greens in my pots on top of the tiny resident ants (Pheidole parva) and occasionally, some small spiders.

Long-flange Millipede looks very similar to another millipede, Oxidus gracilis (Short-flange Millipede). Pictures comparison the two could be found in the Cook Islands Biodiversity website. While Orthomorpha coarctata was listed in the checklist of Singapore millipedes published in 2013 [1], Oxidus gracilis was not. Hence, Oxidus gracilis might not be available here, at least on the record.

Long-flange Millipede had a much larger size cousin, Anoplodesmus saussurii (Flat Millipede) with a length that ranged from 21 to 33 mm. Due to its size, Flat Millipede was much more visible in the park compared to Long-flange Millipede. Report of the Flat Millipede was available in a local article published in 2012 [2]. The article also mentioned another imported millipede, Chondromorpha xanthotricha which I came across in a park in 2009. This millipede only landed in Thailand recently in 2017 [3].

References:

[1] Decker P. Annotated Checklist of the Millipedes (Diplopoda) and Centipedes (Chilopoda) of Singapore. Raffles Museum of Biodiversity Research 2013, pp 29. | Read article |

[2] Decker P, Tertilt T. First records of two introduced millipedes Anoplodesmus saussurii and Chondromorpha xanthotricha (Diplopoda: Polydesmida: Paradoxosomatidae) in Singapore. Nature In Singapore 2012;5:141-149. | Read article |

[3] Likhitrakarn N, Golovatch SI, Panha S. The first record of the pantropical millipede, Chondromorpha xanthotricha (Attems, 1898) (Diplopoda: Polydesmida: Paradoxosomatidae), from Thailand. Arthropoda Selecta 2017;26(4):281-287. | Read article |