Texas Invasive Species Institute

Texas Invasive Species Institute

Giant Garden Slug

Limax maximus

Class: Gastropoda
Order: Stylommatophora
Family: Limacidae

Limax maximus

Photographer: Michal Manas Source:www.wikipedia.org Copyright: CC BY 2.5


Limax maximus is a large (6 in. to more than 8 in.), nocturnal and terrestrial slug in the Limacidae family or the keel back slugs. In the leopard slug the keel is well-marked present towards the posterior end of the body. Another feature of Limacid slugs is the respiratory hole being present in the back-half of the mantle shield. The tentacles are a light to dark brown and it has brown mottling and sometimes lateral bands are present on the posterior end of the body. However, the lateral bands are never on the mantle or head of the snail like a similar species, Lehmannia valentiana.

Ecological Threat

This gastropod eats fresh and rotting plants, more specifically tubers, fruits, and leaves, roots, bulb flowers, ornamental plants, and perennial herbs. Sometimes even carrion of animals. Studies have shown that in Hawaii, temperate slug species like L. maximus negatively affect native plant seedling survivorship creating problems in garden and commercial planting. With a voracious appetite for almost and living or dead plant these slugs can become quite a pest and has also been observed to displace the native Banana Slug, Ariolimax sp in the Northwestern United States. But what makes them even more dangerous is the fact that they can carry the meningitis-causing nematode Angiostrongylus cantonensis. This rat lungworm nematode can infect humans when the gastropod (snail/slug) intermediate hosts are eaten raw or undercooked; however, handling of the slugs bare-handed has caused some infestations in southeastern Asia. This parasite has been found in Norway rat populations in New Orleans and primate hosts in the Miami Zoo, and other zoonotic occurrences but no human cases so far.


Contrary to many other slugs, Limax maximus can survive its first year to grow as old as three years. Even though the slugs are hermaphroditic they cannot impregnate themselves so two slugs are required for mating. Both crawl towards an overhanging part of a wall or a tree branch, from where they rope down on a slime thread about 16 in. long. Hanging freely in the air they then mate by extending their penises and entwining them. Doing so, they make a characteristic flower like structure below them, where the spermatophores are exchanged. After their artistic act of mating, leopard slugs lay as many as 200 large clear eggs, in which the development of the juveniles can well be observed. Freshly hatched leopard slugs are very tiny and pale white in color and, about after a week, they begin to show the first stripes and bands.


It was first discovered in cellars of Philadelphia in 1867 and within a few years sighting had expanded into Rhode Island and New York. In 1896 it was discovered in California and is now present in about 38 of the United States.

Native Origin

Southern and Western Europe, North Africa and Asia Minor

Current Location

U.S. Habitat: These slugs are constricted to living in places where they can have easy access to water since they have poor ability to retain water and easily dry out during the day. They live primarily near human settlement but can be found in wooded areas far away from anthropogenic development.


U.S. Present: AK, AL, AR, CA, CT, DE, GA, HI,  IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MO, MN, MT, NC, NH, NJ, NM, NY, OH, OK, RI, PA, SC, TN, TX, VA, VT, WA, WI, WV


As with other slug species, absolute eradication is nearly impossible. The best way to manage Limax maximus is by early detection and rapid response along with public education to raise awareness of this slug. Please remove any of these pests from your yard but use gloves when handling them!

For a non-toxic solution you can submerge them in soapy water overnight (in a full, water-tight container) and dispose of them the next day. Shallow traps baited with beer or apple cider have shown to be effective, and the slugs can be disposed of in the morning. To discourage snails and slugs on potted plants you can place copper stripping around the base of the pots; and diatomaceous earth often discourages unwanted mollusks in your yard without harming plants. Slugs are susceptible to carbamate insecticides and iron phosphate. These pesticides coordinated with baits can achieve more effective results in reducing the slug populations. However, slug baits are toxic to domestic animals. In Britain and Europe, a predatory nematode Phasmarhabditis hermaphroditais being sold as a biological control for Limax maximus but it is not sold in the United States.

Commercially produced metaldehyde slug traps can be set up to reduce slug populations; but slug bait is very toxic to domestic animals. If you have domestic animals you can use organic slug bait which is iron-phosphate based and NOT-metaldehyde based. Even with the organic slug bait, do not make it easily or consistently accessible to domestic animals.

 ** After handling live slugs, hands should be washed in hot soapy water, and rinsed in alcohol or a standard hand disinfectant. Angiostrongylus nematodes are appearing in Texas, it is encouraged that latex gloves be worn, or at least samples handled using a plastic bag**



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Teem JL, Qvarnstrom Y, Bishop HS, da Silva AJ, Carter J. The occurence of the rat lungworm Angiostrongylus cantonensis (Chen 1935) in nonindigenous apple snails in the Gulf of Mexico region of the United States. Hawaii J Med Public Health. 2013;72(6 Suppl 2):11–14.


Internet Sources





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