The Distribution and Abundance of Slugs on an Arable plot in Northumberland

Abstract

The variations in numbers of slugs on an arable plot at Close House, Northumberland (Grid Reference NZ 127658), were studied during a series of samples between January 1963 and March 1965. The plot, 15 x 25 yd (14 x 23 m), was on a loam soil in a market garden of about 2ac (0 8 ha). The dominant species on the plot were Agriolimax reticulatus (Muller), Arion hortensis Ferussac and Milax budapestensis (Hazay). Their life cycles in this area are as follows (Hunter 1966b): Agriolimax reticulatus has two generations per year, a spring generation hatching about May and an autumn generation hatching about September. Individuals hatching in autumn take longer (7 months) to complete their life cycle than those hatching in spring (5 months). Arion hortensis usually has an annual cycle, hatching about July and maturing and laying eggs at about a year old. A few, however, hatch later and are not ready to lay eggs until after their second winter, thus taking almost 2 years to complete their cycle. Milax budapestensis has usually a biennial cycle. The eggs hatch between May and August and individuals grow in weight during the following 18 months (except for a pause in growth during the winter) to mature during their second autumn. A few hatch as early as April and have grown enough during their first year to mature during their first winter.