In the UK the lugworm species "Arenicola marina" is commonly called blow lugworm, and rarely exceeds 130mm (roughly 5 inches). There is a second species of UK lugworm "Arenicola defodiens" commonly called black lugworm. As well as growing larger than blow lugworm (in line with descriptions for Europe and North America lugworm below) they are generally much darker, often totally black. They can be distinguished by the different wormcasts they produce - "Arenicola defodiens" makes a spiral cast, while that of "Arenicola marina" is jumbled.