Black Slugs

05 April, 2009

Two Black Slugs, <I>Arion ater</I>
Two Black Slugs, Arion ater
Image: Dr. Brian J. Smith
Source: Dr. Brian J. Smith

Question: I have found several of these large black slugs in my garden. I haven’t come across them before. Can you tell me what they are? I was also wondering if they are native or introduced and whether they are likely to cause much damage in my garden.
 
Answer: Thank-you for sending your slug to the Discovery Centre at Melbourne Museum. We sent it to our invertebrate department and they have identified it as the species Arion ater (commonly known as the Black Slug).
 
Black Slugs are large land slugs; a fully-extended adult can be 15 cm long. They have a dark brown to black body, occasionally mottled to variegated with rows of prominent tubercules. Their foot is fringed with black and orange or yellow stripes. Black Slugs cover themselves in thick, sticky mucus which serves to keep them moist and protect them from predators (it apparently tastes quite foul). This mucus can be quite difficult to remove from our skin.
 
Black Slugs are native to Europe. They are considered not to be good world travellers and, until recently, their presence in Australia has only been recorded in a few localities. The Melbourne Museum Discovery Centre first received a request to identify a Black Slug in 2001 and we have only received one or two enquiries about this species each year since then.
 
Black Slugs are still not considered to be established in Australia. However, from what we’ve learned from the members of the public who have sent them in, there is a population of these slugs in the Dandenongs (one enquirer reported that he had collected 4000 Black Slugs on his Dandenong property).

In 2005, we received a specimen from the Otway Ranges (this was the museum’s first record of Arion ater from this area).  Records from other museums show that the species is also present in parts of New South Wales and South Australia. So far at least, they seem to be restricted to gardens and similar cultivated habitats.
 
Black Slugs are regarded as garden pests in Britain and Europe. They can cause damage to seedlings in spring, but their preferred diet consists of rotting vegetation, fungi, manure and even dead animals. Despite their unpleasant-tasting mucus, Black Slugs do have some natural predators. These include hedgehogs, badgers, shrews and moles. None of these species occur in Australia.

Comments (62)

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Carol Wilmink 3 March, 2010 20:53
Half a plastic bucket of these black slugs were collected in half an hour yeasterday along riverflats of the Barham River at Apollo Bay. Previously we have only noticed 2 or 3. We have drowned them in salt water. We are treating them as invasive pests. Would these still have any viable eggs we need to dispose of?
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Discovery Centre 5 March, 2010 15:10

Thanks for your query about slug eggs. We've sent this to one of our experts and will get back to you with an answer as soon as possible.

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Carol Wilmink 6 March, 2010 10:39
Since my last comment we have collected another half a bucket of these black slugs. A quarter bucket contains 250, as we counted the last collection done yesterday, a dull humid day. That's about 1000 slugs. We have 5 Kms of river flats between us and the sea. It is a tourist area. Is there potential for a black slug invasion of our environment, to the detriment of our native species, e.g. rare Otway black snail?
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Discovery Centre 10 March, 2010 12:09

Sounds serious, Carol. We'll get back to you as soon as we've heard back from the relevant Collection Manager.

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Discovery Centre 10 March, 2010 15:46

Okay, Carol. We've been in touch with staff in both our Live Exhibits and Invertebrates areas who have come back with their advice. Regarding the eggs, it's likely that the salt-water solution will have been sufficient to rupture the walls of the eggs and kill them effectively. Ammonia would be another effective solution. As for the outbreak, our records suggest that populations of Arion ater seem to occur between November and March, usually following periods of wet weather. As recently as 2007, the species was reported as "no longer in Australia," despite isolated pockets in the Dandenongs and Otways that provide suitable conditions for them to establish breeding populations. It's because they are not widely recognised as "established" in Australia that there is such a dearth of literature on their potential distribution and their effect on native fauna and flora.

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Abigail Schultz 17 March, 2010 14:17
Hi, I would like to add to Carol Wilmink's comments regarding these slugs in the Otways. I was walking through the paddock at my parents property in Apollo Bay and there were honestly 100's of these slugs, they were everywhere. They were not there last year, but suddenly they are in huge populations. Is this an issue, should someone be looking into this as a potential problem? All I can hope is that the local snakes/lizards like to eat them... What should I do?
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Discovery Centre 17 March, 2010 15:44

Thanks for this information, Abigail. We've passed it on to staff in the Museum. Unfortunately we cannot offer advice about controlling the pest. You may consider contacting a professional pest-controller about the problem. The Department of Sustainability and Environment would be the people to contact about any collective response to the outbreak; we're sure they would appreciate localised reports such as these.

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Carol Wilmink 8 November, 2010 18:57
I was just checking to see if Museum Victoria had received any more queries about these black slugs - as they have 're-surfaced' at our place in Apollo Bay - and I still can't find any government department that thinks they may be a threat to our local environment! Now 8-11-2010, so I will start my 'Black Slug - Arion ater - awareness' campaign. ! Thanks for your initial information.
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Tim Cannon 7 December, 2010 21:38
These little guys may be more widespread in Victoria than those isolated pockets. This afternoon I found a solitary black slug grazing on my lawn in Central Victoria (just north of Maryborough). Hopefully I don't find any more... all this rain has cause an explosion of gastropods!
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Paul Bennett 15 December, 2010 15:37
I have found one individual in lush grass on top of MT Dandenong.15/12/10.
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Sean Pie 25 December, 2010 21:18
We have just found two of these huge slugs in our garden in Kalorama (Dandenong Ranges). Have never seen them before.
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Roana Greg and Connor O'Neill 26 December, 2010 19:49
On a short walk along One Tree Hill Road in Ferny Creek in the Dandenongs today 26th Dec 2010 we came across 50+ of these black slugs ranging from 7 - 12cm long. We just hopped on your site to find out more about them as we found them fascinating - but it's dissapointing to see they're not native after all. We guess the unusual wet conditions have brought them all out. Thanks for your info
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NL 31 December, 2010 20:46
I am in Olinda, right near the Pig and Whistle. There are lots and lots of these large black slugs in our back garden, just lying in the grass. I could easily find 10+ of them in one area without even trying. I sincerely hate killing little creatures unless really necessary. Does anyone know whether there are any predators here that will eat them? Is it considered that these slugs are a potentially dangerous introduced species, and I should really kill them? I am kind of hoping that the chickens might eat them, but if they taste nasty maybe they won't? Any advise on whether extermination is required would be appreciated?
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Discovery Centre 5 January, 2011 14:52
Hi NL and Nigel, regarding the large, black slugs you are seeing in the Dandenongs. We were sent large black slugs a few years ago from the Dandenongs that we identified as Arion ater. The size of your slugs sound a little bit bigger than we remember Arion ater as being. Leopard slugs on the other hand, are generally light brown to grey with dark brown to black bands on the body and dark spotting or marbling on the mantle. Both species are introductions from Europe. If either of you are able to get some images of the slugs, (with a ruler or something for scale) and email them to discoverycentre@museum.vic.gov.au we can try and identify them for you.  

 

We really need to see an image or examine a specimen to be sure.

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Rob Lawther 6 January, 2011 20:56
Hi, we have a 12 acre property at merango in the foothills just beyond Apollo Bay township. I just found a solitary black slug grazing on our lawn. I will attach a photo. It is about 15 cm fully extended. Rob
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LF 14 January, 2011 22:57
Hi, We live on a property in Ferny Creek and have hundreds of Black Slugs - some as large as 160mm in length. Crows and Kookaburras aren't interested in eating them and I watched as trapdoor/ground spider try to attack one and give up. I have been thinking they might be a good exotic pet option for emo's! I thought they were a type of Leopard Slug - but am now not sure. will send some photos. L I'll send some photos.
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Kerry Dawborn 18 January, 2011 20:04
A friend and I were just this evening walking along a new walking track in Ferny Creek - I think it's called the Tan and being officially opened tomorrow, and spotted about 30 of these slugs in the grass by the side of the track. Is there some program to humanely control or eradicate these introduced critters? I hate to think of it, but at the same time they seem from other's observations to be extremely resilient, and it would be horrid to see them wreak devastation....
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Discovery Centre 22 January, 2011 16:09
Hi Kerry, unfortunately the Museum can't advise on pest control. The Department of Sustainability and Environment may be interested in knowing about your sighting.
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Robert Wertheimer 26 January, 2011 10:01
I have a farm in Wongarra midway between Apollo Bay and Lorne. In previous years we have seen a few black slugs, but this year they are widespread across the farm and in their thousands. The speed of their spread is concerning. Nothing seems to be interested in eating them. I am looking to see if they are thriving in the national park.
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Sue white 26 January, 2011 15:43
Working at Sassafras in the Dandenong Ranges this morning-damp and misty and uncovered three Black Slugs on the property in a garden bordering the Tourist Road. Awesome looking creatures even if a pest!
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Nancy 15 February, 2011 19:52
I live in Kalorama and am being over rum by these revolting things-they are everywhere. I have just disposed of 12 of them that were in 1 sq/m in my garden. Any natural ways to repel them?
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Discovery Centre 16 February, 2011 14:01
Hi Nancy, unfortunately we can't advise on control meaures as this is not an area that we are involved in or have expertise in. As we have suggested to a few other enquirers the Department of Sustainability and Environment may be keeping an eye on these or may want to hear about reports.
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Joel 16 February, 2011 19:11
I'm a landscape gardener in the blue mountains - i was working on a large property in Katoomba yesterday and came across literally thousands of these giant black slugs, they were absolutely everywhere. Never seen anything like it in all my time in the mountains.
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Carol Wilmink 17 February, 2011 10:50
We have now collected and disposed of over 20,000 of these black slugs; that does not include 'juveniles', which may be white, amber or brown. Dr Mallik Malipatil, DPI, positively identified them in Nov 2010 and said that DSE would contact us if they were concerned. They haven't, but we are!
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Lyn 25 February, 2011 12:40
I live in the hills near Apollo Bay. I have grown dahlias for 30 years but this year the black slugs have not even given the shoots a chance to grow. They have also severely limited my choice of vegetables to grow. Some authority needs to do something to get rid of them fast as they must be seen as a serious threat to home and professional gardens.
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Kerry 27 February, 2011 20:21
I live in Belgrave, on the edge of the Dandenongs, and we haven't had any black slugs in our garden yet. Lots of leopard slugs, which like the pea straw on our veggie patch though! Anyway, in the UK the black slug is a fearsome foe of any gardener and they're pretty disgusting. We simply collected the black slugs and used a bucket of salt water to dispose of them. The slugs go in the bin (or compost heap) and the water then goes down the drain.
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Katy 28 February, 2011 10:27
Add Kallista in the Dandenongs to the list of places where these slugs have been sighted in recent years. They're on the march.
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Kathy Munro 1 March, 2011 11:48
I live In Warragul, Victoria and have just seen my first investation of these black slugs near a commercial nursery. There were at least 30 of them and they are huge! I am sure they will compete with native leopard slugs. They also have no predators in Australia as birds etc find them distasteful. Hope DSE look into this growing problem.
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Stephen Richards 6 March, 2011 23:14
Kallista Victoria sightings again of big black slugs. I have a family of four that come out every night to graze on the lawn. 30 years here and never seen them before.
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Kevin Bonham 9 March, 2011 23:40
First Tasmanian records have come in in the last year or so, mostly from the Wynyard area.
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GLENDA WHELAN 20 March, 2011 12:44
As with Carol and others I have found the black slugs to be infesting our property on the hills overlooking Apollo Bay. My method of control is to scoop them up into a bucket of soapy water. I collect between 10 and 40 each evening within 10 mins around my vegie garden ,paths, driveway and on the lawn directly around my house. They will decimate a seedling in minutes and have started eating full grown zucchinis. apart from collection I have found no way to control them. If they get into areas where there are market gardens ie around Werribee, it will be a disaster.
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andrea 3 July, 2011 09:55
Hi we have many black slugs in Wallan, Vic are they spreading? most of the comments say they are in the east and west but we are north!
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Neville Brown 25 July, 2011 16:37
They are not just in Victoria. I have seen varying numbers in the Adelaide Hills since 2002.
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Giselle 4 November, 2011 10:13
I live in the Dandenong Ranges (Ferny Creek) and have watched in astonishment as a sighting of two black slugs three years ago became a count of up to fifty on my walk yesterday - and that is just on the path. The walk is right next to the National Park. I've taken photos as they each seem to have a 'hole' in their skin, on the rhs behind the head.
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Jeff 6 November, 2011 11:05
I first saw one these slugs in a plant nursery. Obvious hitch hiker. Recently we moved back to the Dandenongs in Kalorama. I noticed a couple of these slugs with in a short time. The rear of our property is large lawn area where hundreds can be seen during the day. They seem established. Thanks to this site I have come to learn more about them
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Stephen Richards 16 November, 2011 14:27
Kallista Dandenong Ranges Victoria. They are back again with the spring rains. Do not want to hurt these little creatures but expect they might breed up in numbers with the right conditions. Will monitor over next few weeks. These are pests and so I should about how to control them before numbers become alarming like others describe in the blog.
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Phil Went 9 December, 2011 10:13
We are getting these in the blue mountains in NSW for the first time but in large numbers. As the towns are at the tops and junctions of hanging swamps that feed into the national park it is a real worry they will become a serious pest in the park.
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Rob Smyth 17 December, 2011 21:24
I'm in Sassafras (that's the Dandenong Ranges - NOT the same place as Dandenong, which your original answer mentions). We've had these slugs in hundreds in the garden for perhaps the last five years. As noted above, they prefer to stay on the ground and live on rotting vegetation. They appear after rain or when there's dew on the ground and then disappear into cool, moist places until conditions are favourable for them again.
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Rae Mitchell 18 December, 2011 21:37
I've just collected around 50 from our lawn and deck area! We live in Hahndorf on a small property in the Adelaide Hills. Previously we have collected up to two dozen at one time. We've just had quite a bit of rain so it has brought them out in bigger numbers! We find sprinkling a little salt on their backs an effective way of getting rid of them!
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Andrew Chapman 21 December, 2011 20:30
There are hundreds through the lawns along Ridge Rd in Kallista. The crooks like them!
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Denise Dempsey 9 January, 2012 22:20
We live in Sassafras and have had them for about 5 years. They are in huge numbers at the moment - wiped out all of my carrots! Andrew said crooks like them - what are crooks?
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Rob Lawther 11 January, 2012 13:12
Hi, further to other comments, I have a property near Apollo Bay and I had a couple of European black slugs this time last year to hundreds this year, it is something that the authorities need to get their act together on. I have decided to destroy all that I can find to at least protect my property from the invasion. Rob
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Discovery Centre 11 January, 2012 15:03

It sounds like it could possibly be Arion ater, (a large & black slug introducer from Europe) however we really need to examine the specimen in order to provide an accurate identification.

Based on the few records that we have, population explosions of Arion ater seems to occur from around November - March, usually following periods of wet weather.

It is interesting that as recently as 2007, Arion ater was reported as “no longer occurring in Australia”, however contrary to this report, it seems that a few isolated pockets in the Dandenongs & Otways provide suitable conditions to for them to be able to establish breeding populations.

Since they are largely not regarded as being established, there is a dearth of literature available on their potential distribution or their effect on native fauna & flora.  

Unfortunately, Museum Victoria is not qualified to provide advice on how best to eradicate slugs.  

Nina 19 January, 2012 23:00
i live in Wentworth Falls in the blue mountains NSW. We have thousands of these things in our yard. Big infestation. Bane of my life right now.
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Susan Day 2 February, 2012 15:19
We have been seeing more and more of these huge slugs on our property. Wer are at Blackheath in the Blue Mountains, NSW amd have a nursery next door. They started coming from over there.
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John 10 February, 2012 20:13
Add Kilmore Vic to the list, north of the divide from Wallen, have about 30 on the back lawn and one so far at the front.
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Genevieve Jones 16 February, 2012 12:43
I too, have discovered many of these creatures in my garden after wet weather. So many its almost impossible not to step on them. Ive also noticed many have some parasite living and eating huge holes in their bodies. Anybody know what's going on?
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leanne Fewings 15 March, 2012 20:27
FYI have just sighted about 10 of the arion ater at the end of Crabtree rd Huon valley in Southern Tasmania.
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Gail Murphy 16 March, 2012 15:52
I live on the border of Kalorama and MT Dandenong. The slugs are on the increase. Killing is not my forte yet, with an apology I don't hestitate killing them with the nearest stick that is strong enough. Perhaps soapy or salt water is kinder, or freezing perhaps: I will be trying the beer in the dish trick. A friend said there was a segment on the box, that said they were pests that caused a rust/fungus?. All I know at this stage is that a Leculia that is over 50 years old is dying back suspiciously. If a specimen is needed I will be happy to show you many.
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Discovery Centre 17 March, 2012 11:57
Hi Gail, the Museum is not currently researching these slugs but could find no research online that suggests these slugs are capable of transmitting a rust to plants.
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Deanna 31 March, 2012 15:28
I had one of these huge slugs in my yard today. I had never seen Anything like it so I did a little research. They are native in Europe... So why was this little critter in my Texas garden in the USA? Can't figure that one out.
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Discovery Centre 2 April, 2012 10:38
Hi Deanna - as we state above, Museum Victoria is not currently researching these slugs, and we do not have expertise on their distribution outside Australia - you will need to contact a local Natural History Museum or Government Wildlife body for information on this species in the USA.
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Lauren 21 April, 2012 20:31
Hi, I have a record from Jones Park, East Brunswick, in Melbourne's inner north. Single black slug seen in grass on 20 April 2011. No photo sorry, running late for work but I've never seen one before, it was black as pitch and really caught my eye. Will photograph the next one I see. Regards, Lauren
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Shannelle 22 July, 2012 07:02
Well me and some friends went to Whittier,Alaska yesterday for a trip and we were by the water just looking around for shells and stuff laying around. We came across these long black slugs and they are really disgusting. It says they came from Europe? How did they get here in Alaska? I got some pictures and a cpl videos of them.
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Discovery Centre 22 July, 2012 09:25
Hi Shannelle, feel free to send your images to discoverycentre@museum.vic.gov.au We have a slug and snail expert who may be able to confirm the identity for you. It may also be of use for you to contact the Alaska Museum of Natural History, they may also be able to confirm the identity or have some further information on these slugs in your area.   
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Lawrie Yovich 31 January, 2013 19:33
We have just identified a number of these slugs on our property at Wynyard in Tasmania . Just wondering if anyone else has reported seeing these slugs in Tasmania before?
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Shannon 16 February, 2013 09:32
We live in Kallista and the number of black slugs has increased over the past 3 years.
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Renato 28 April, 2013 13:32
UNUSUAL REQUEST: I am urgently looking for BLACK SLUGS and BLACK SNAILS for a photographic shoot. I will pay for each live sample and for the postage. NB URGENT. Thank you!
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Wendy 9 December, 2013 23:46
Thank you for the information on the black slugs. I live in Olinda and after discovering that my vegetable and herb garden were being attacked,I went out with a torch at night and collected about 100 on the first night. Each night now I go out and usually collect about 50 to 100, mostly on the lawn. I feel really cruel but I put them into a plastic bag and freeze them. I am worried about how many there are this year. I first noticed a couple 2 years ago.
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Stephen Richards 5 March, 2014 21:29
Kallista in the Dandenongs. Two in the lawn. First sighting in two years. Will monitor numbers before taking any action.
Mrs M 11 April, 2014 21:20
I found these slugs in lavers hill otway ranges I hope that they don't effect the local native glow worm population. I read that these slugs are also host to the French heartworm.
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Lee 26 October, 2014 17:38
I found one today in Adelaide. Just one though. It potentially hitched a ride with plants from Victoria maybe. I somehow don't think they will like our dry Mediterranean summer though.
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