Snails and Slugs of the Pacific Lowlands

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Oregon Forest Snail Pacific Sideband Brown Garden Snail Garlic Snail Banded Wood Snail
Robust Lancetooth Banana Slug Black garden slug Giant garden slug Milky slug

 

 
Oregon Forestsnail  Allogona Townsendiana

Identifying Features: Dark brown bodied snail with brown shell with concentric lines.  Upper whorls often pale from wear.

This is a snail of moist mixed forests, and are found most often in the company of Big-leaf maples. They are most noticeable during spring and sometimes may be found in small mating groups. They eat a variety of plants but at times prefer nettles and in the early spring they are the culprit who creates the large holes in the newly sprouted nettle shoots.  Eggs are laid in May, hatch in June and the young disperse immediately.  During the dry summer months they take refuge under moist litter, become active again in the fall until the first frosts, where they then hibernate until the following spring.  They take 2 years to full grown size and may live up to 5 years.
 


 

 
Pacific Sideband Monadena fidelis

Identifying Features: Shell, rosy brown with a thin black line in the bottom whorls

A snail of mossy cool forests. Most active during wet warm months, forages on vegetable matter of all kinds and fungi, then returns to a refuge which may be under leaves or woody debris. Sometimes they hibernate in moss, has been found hibernating in thick moss on a Big Leaf maple branch but more often they utilize rock piles as summer and winter refuges.

 Eggs are laid in Spring in loose soil. They take 2 years to grow to maturity and may live up 6 years.
 
Brown Garden Snail  Cantareus aspersa

Identifying Features:  Streaked brown shell, white or gray body.

This is a serious garden pest in other states and has moved into the Pacific Northwest much to the dismay of gardeners everywhere. It was  brought from Europe as a food delicacy and they have been a pest in California for more than 100 years. 

They come out at night from moist hidden areas and munch garden plants. They readily climb walls and trees and are especially a problem for greenhouse growers.
 
 Garlic Snail  Oxychillus  alliarius

Identifying Features:  Small snail, flat shell,  pale yellow green almost translucent, body black.

This snail gets its name from the strong garlic odor it emits as a defense. Since this is a snail from England, the primary reason for the smell to is deter hedgehogs which are repelled by the odor.  Like most snails it eats a wide variety of plant material. It can most often be found under pots or other cover in gardens.

 

Banded Wood Snail  Capea nemoralis

Identifying Features: This is a widely varied patterned snail, sometimes with distinctive brown, yellow whorls alternating with white, Sometimes mostly yellow with one or two black bands. 

This European import breeds in summer and spring, often they may become very active after a heavy spring rain. 

Takes 3 years to reach full adult size, may live up to 5 years.  A snail of fields and pastures, sometimes very localized and numerous, hundreds can sometimes be found under a large board.  They readily climb into shrubs and trees. The bleached empty shells can sometimes be found with a tiny snail inside.
 
Robust Lancetooth  Haplotrema vancouverense

Identifying features: Shell flattened rather than conical, yellowish to green with fine banding.

This snail, unlike most of its brethren is a carnivore, snacking on other snails. They get the name Lancetooth from a calcium carbonite spike which they stab another snail with, then follow the slimy trail until the victim dies. They also readily attack and eat small slugs and earthworms with the same methods.

 
Banana Slug   Ariolimax columbianus

Identifying Features: Large size, up to 8 inches long, often green or yellow.

This is the big daddy of the native slugs, found in moist forest floors throughout the area. Like all slugs they have two sets of tentacles, the upper for sensing movement and light, the lower for smelling and tasting.  They eat decaying plant material and have a particular fondness for mushrooms.  They must stay moist and often become nocturnal, foraging from a moist cover such as a moss covered fallen log or other refuge and then returning. During wet seasons they are active during the day as well as night. Mating occurs in the spring or fall and 20-30 eggs are lain in a high humid, covered situation.  Eggs hatch within two months into almost clear young slugs which then disperse and forage and must find refuge from drying out.  Banana slugs live up to 5-6 years and often change colors during the year in response to what they are eating, light or to moisture conditions.  Slugs are preyed upon by shrews, raccoons, and Scaphinotus beetles.

 

 
Black Garden Slug  Arion ater

Identifying Features: Large brown slug, up to 5-6 inches, sometimes reddish edge to foot, furrowed lower half, black antenna.

This European import is the bane of Northwest flower and vegetable gardeners. In our area they are mostly brown.  It is mostly nocturnal although it may be afoot on cool moist days.  Like all of its kind it needs to stay damp so it takes refuge under rocks, boards, old logs or in compost piles. When moisture stressed it can hump itself up into an almost round ball, which preserves essential body water.  Eggs are lain during the moist spring and fall, fall eggs overwinter.  The young slugs take up to a year to mature.  These slugs can travel up to 1/4 mile in search of better conditions, which is a long migration for such a slow animal.

 

 
Giant Garden Slug (Leopard Slug)  Limax maximus

Identifying Features:  Gray to light green brown body with distinctive black spots and lines.

This is another European invader of gardens and lawns. It is quite large, up to 6 inches when full grown but mostly nocturnal and so rarely seen except in early morning on wet spring or fall days.  Like all slugs it must maintain its moisture and so it hides under damp cover to which it retreats during the daylight.  Of all the slugs it has the least sticky slime but it is also pretty speedy for slug with a top speed of 6 inches in minute.  When mating two slugs follow each other for many hours before finally climbing up a shrub or tree.  They entwine and dangle down on a thick mucus line, swinging  in the breeze as they mate, a process which may take several hours. Like most slugs, they are hermaphrodites, each slug fertilizing the others eggs.  They must then untangle and since the penis is barbed, it often requires chewing off the genitals of the partner.  Each slug then lays hundreds of eggs in moist high humidity covered areas.

 

 
Gray Garden Slug (Milky Slug)  Deroceras reticultatum

Identifying Features: Small slug, 2 inches with light gray body and mottled with brown or black.

Another European pest, this one smaller but lays hundreds of eggs which hatch during early summer into small sluglets which devour garden crops and flowers, with a special fondness for strawberries. It gets the name Milky slug because when disturbed it exudes a white slime, unlike most slugs which is clear.   Fall eggs overwinter and so by the warmth of late March these tiny munchers are feasting on your new veggie garden. The European garden beetle, Carabus nemoralis, eats the young slugs and also the eggs.