Milax gagates

Biological Name

Milax gagates (Draparnaud, 1801)

Common Name

Black keeled slug

Other Common Names

Greenhouse slug


Black keeled slugs are 50 to 60 mm long, the pneumostome is located in the posterior half of the mantle. Its colour is dark grey or brown with a darker keel running along its back. The mucus is colourless.

Other Similar Species

Tandonia budapestensis

Biological Notes

The black keeled slug is an annual species with a life span of 12-14 months. It is a true burrowing species and can tolerate relatively dry conditions.

Geographic Distribution

It is widespread in Southwest Europe and common in New Zealand, Japan, Australia, South Africa, USA, Argentina.


Even though the black keeled slug can survive drier conditions than most, it prefers habitats close to water. It lives mostly in cultivated areas, hides under stones and in soil cavities.

Crops at Risk

The black keeled slug is a relatively more serious pest in dry areas. It damages potatoes and carrots but feeds also on fresh herbs and germinating seedlings of sunflower, oilseed rape and soybean crops.

Damage Caused/Symptoms

It causes damage to seeds and seedlings and feeds on the soil surface and below the ground.

Impact and Severity

In dry habitats and under no tillage systems the damage of the black keeled slug increases.

Prevention and Control

The slug-parasitic nematode Phasmarhabditis hermaphrodita is used as a biological control agent against the black keeled slug.

Natural Predators

The black keeled slug is a prey of several, field-inhabiting ground beetle species.