Prawns in the house?

02 August, 2009

Land Hopper - Arcitalitrus sylvaticus.
Land Hopper - Arcitalitrus sylvaticus.
Image: David Staples
Source: Museum Victoria

Question: I don’t live near the beach but keep finding prawns in my house – why?

Answer: These invertebrates are not prawns but a species of amphipod, commonly called land hoppers or lawn shrimps. There are thousands of species of amphipods, the majority of which live in the marine environment. However a number of species are terrestrial and they all require a moist environment in which to survive.

Amphipods are laterally compressed meaning they are taller than they are wide. It may be for some of the marine species that this aids in moving through dense plants. If you have ever lifted a pot plant or raked through leaf litter in a forest or even your garden you may have noticed these land hoppers jumping around. They can achieve this by a sudden flexing of their abdomen and the random and rapid way in which they jump around makes it hard for predators to catch them.

Amphipods are an important food source for many animals in the sea and on land; amphipods themselves generally feed on decaying plant material but there have been some cases of cannibalism.

Sometimes following heavy rain amphipods can be flushed from their usual home in leaf litter and end up coming into peoples homes or garages or falling into their swimming pools. Usually on coming inside they rapidly dry out and die and many become a red or pink color, again contributing to people thinking of them as prawns or shrimps. These invertebrates should not cause any damage to the contents of a house and present more of a nuisance value than anything else. If they come inside and die, simply sweep them up and throw them out.

Try not to have moist, deep leaf litter near doors as this may encourage populations of amphipods and if you get repeat incursions of amphipods into your home try making the cracks under the door smaller by using draught excluders.

References

Melbourne’s Wildlife: a field guide to the fauna of Greater Melbourne.
Published by Museum Victoria and CSIRO Publishing, 2006.

Comments (12)

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Hubert 23 October, 2010 02:46
Thank you thank you. It has just rained here for past week and I found these everywhere outside. All over our patio and in dogs bowls and jumping all over the wet dirt. I am so glad they are harmless even though they are ugly
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Anita 29 May, 2011 22:27
Thank you for this information! I keep finding them at my back door and under the mat as well. I have started to clean up my backyard and I found some live ones. Now I know what they are i'll just keep sweeping them up.
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loretta dodds 29 September, 2011 13:32
these seem to come in my house at night..can I get rid of them springwood qldeight
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Discovery Centre 29 September, 2011 15:17
Hi Loretta, these creatures can be hard to keep out, have a read of the last couple of paragraphs which has some suggestions on how to try and keep these invertebrates out of the home. Remember that even if they do come in, they pose a nuisance value only, they don't bite people and usually die very quickly after coming into homes. If this does happen you can just sweep up the bodies and throw them out.
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Jodie O'Connor 28 October, 2012 20:28
My boyfriend plus a couple of other friends have been bitten by something we cannot see . Myself, Mother and daughter have not. I have sprayed, washed everything but to no avail. Finally, i had the pest man and come to spray. Today i have found these lawn shrimps which i swept up. Do they bite or cause very itchy raised lumps? We have not had any rain here in Brisbane for a long period. In fact it is extremely dry. My dogs scratch also and they have been bathed. Please help! I have never seen these things in my life. J
Discovery Centre 29 October, 2012 10:07
Hi Jodie, no these invertebrates don't bite and shouldn't cause the problems you describe. The best thing may be for your friends to visit their doctor and show them the physical evidence they have; they may have an allergy to something that a doctor or dermatologist can assist with. 
Nina 8 March, 2012 14:21
Hi, I have these too however they are biting my dogs quite nastily and have covered them in bites, do they live on animals? what do they feed on? please help
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Discovery Centre 9 March, 2012 14:42
Hi Nina, we have never heard of these amphipods being a problem for dogs. Terrestrial amphipods are usually found in moist areas, feed on decaying plant matter and don't live on dogs. I doubt that they would seek the dog out; has it been lying in mulch or something similar. Are you sure the bites are from amphipods and not fleas or ticks.
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Lisa Tillott 19 March, 2012 13:13
I find these landhoppers only in our dogs water bowl how do they get there? Someone said they might be in his food and get in the water when he drinks would that be right?
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Discovery Centre 20 March, 2012 09:22
Hi Lisa, terrestrial amphipods generally feed on decaying plant matter and require a moist environment to survive. They would not survive in dry dog food and I doubt would be attracted to it. It may be that the dog has been scratching around its water dish and disturbing the amphipods. When they are exposed they jump in the air and may be ending up in the water bowl? If the dog were to drink a few of these they shouldn't pose any risk.
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Helen Watret 20 August, 2012 17:46
Thank you so much for the information. We are currently on holiday in Fife in Scotland and have been infested with these little critters for the past 3 nights. Never seen anything like them before. We have put tape over the crack in the front door so now only a few get in. At least they are harmless but are a bother to hoover up every morning.
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LeStryge 7 September, 2014 09:08
These critters are a real nuisance in my swimming pool. It is not unusual to have to scoop out three cupfulls or more of pink corpses after a little rain. This huge amount of rotting organic material puts a huge strain on water sanitation. Is there any way I can eliminate, or at least reduce the population of these pests? There has to be some sort of a spray? They seem to live in the cracks between the pavers.
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