(Meder in Philippi, 1847)
Like all snails in the clade Neogastropoda, this species is carnivorous. It feeds on worms and gastropods, and is often known as the "assassin snail" for its habit of eating other snails. These snails will often feed on larger snails, often burying themselves and ambushing their prey.
Clea helena may be a serious threat to native freshwater gastropods in countries, when introduced.
This snail will typically grow to 0.7-1.25 in (20-35 mm) in size depending on food sources, usually smaller in the aquarium. The shell, which is conical in shape, consists of dark brown and yellowish tan bands, leading to some people to refer to this snail as the bumble bee snail, a name also applied to the marine snail Engina mendicaria. The snails will spend much of their time buried in their substrate. They are least active during mid day, however they can sense food and will become active if fed. 
Clea helena consists of defined male and female individuals which are not hermaphroditic. Currently it is not known how to identify which is male and which is female. Both males and females seem to be the same size and shape. When a male and female mate, they lock together for many hours. The female lays several clear egg capsules which are square in shape and approximately 1.0 to 1.5mm in width and height. Each egg capsule contains a single small yellow egg. The egg capsules are generally laid on solid surfaces such as plastic and often on the base of plants. Fertile eggs usually hatch within a few weeks. 
- The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 27 August 2014.
- Bouchet, P.; Fraussen, K. (2013). "Clea – H. Adams & A. Adams, 1855". World Register of Marine Species. Retrieved March 2, 2014.
- Monks, Neale (2009). "Assassin Snails and Sulawesi Elephant Snails: Keeping Clea and Tylomelania in the aquarium". Conscientious Aquarist Magazine. Retrieved March 11, 2014.
- "Map of Clea helena". Discover Life. National Biological Information Infrastructure. Retrieved March 8, 2014.
- (Thai) Boon-ngam P., Sriyarun J., Tanamai S. & Dumrongrojwattana P. (PDF file created 12 January 2010). "การศึกษาเบืองต้ นความหลากชนิดของหอยทากบก และหอยนําจืดในจังหวัดสระแก้ ว Preliminary taxonomic study of land snail and freshwater mollusk species in Sakaeo Province, Eastern Thailand". 10 pp., pages unnumbered. PDF.
- Mienis K. H. (2011). "Will the Uncontrolled Sale of the Snail-eating Gastropod Anentome helena in Aquarium Shops in Israel Result in Another Disaster for Israel's Native Freshwater Mollusc Fauna?". Ellipsaria 13(3): 10-13.
- Newel, M. S.; Bourne, G. B. (January 5, 2013). "The 'assassin' snail, Clea (Anentome) helena (Gastropoda: Buccinidae), as a model for developmental and environmental physiology" (PDF). Society for Integrative and Comparative Developmental Biology 2013 Annual Meeting.
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