This land gastropod is Parmarion martensi. It belongs to family Ariophantidae. Some gastropods from this family has a reduced shell. The shell can be so small in some Ariophantidae species, that they can not retract into it. Such gastropods are called semi-slugs.
I thank my friend Doubravka Požárová, the botanist from Charles University in Prague, who kindly provided the following photos to readers of this blog:
Photos were taken in the surrounding of Lempuyang Temple (Pura Lempuyang Luhur) in the eastern Bali, Indonesia in 2014. It was crawling on the road. I identified the species according to photos only.
Parmarion martensi can reach body length up to 45 mm. It has caudal horn on its tail, but it is not clearly visible on this photo. This species is very variable in color.
Parmarion martensi is native to Southeast Asia. Unfortunately it is able to spread by human activies. It has established in Fiji, Samoa and Hawaii. It was also recorded in the USA. It can be a pest on agricultural crops, but not serious one. Moreover it can transfer nematode Angiostrongylus cantonensis, that can cause human disease. Therefore it is an important species and for example it is quarantine species in the USA.
Brodie G. & Barker G. M. (2012). “Parmarion martensi Simroth, 1893. Family Ariophantidae“. ‘USP Introduced Land Snails of the Fiji Islands Fact Sheet Series’, No. 1
Cowie R. H., Dillon R. T., Robinson D. G. & Smith J. W. (2009). “Alien non-marine snails and slugs of priority quarantine importance in the United States: A preliminary risk assessment”. American Malacological Bulletin 27: 113-132.
Hollingsworth et al. (2007). “Distribution of Parmarion cf. martensi (Pulmonata: Helicarionidae), a New Semi-Slug Pest on Hawai‘i Island, and Its Potential as a Vector for Human Angiostrongyliasis“. Pacific Science 61(4): 457-467. doi:10.2984/1534-6188(2007)61[457:DOPCMP]2.0.CO;2