Outdoors

Here’s why they are called lawn shrimp

One of the more unusual creatures to find its way into our lives is the lawn shrimp.

These wee beasties, known as house hoppers in Australia, aren’t insects. They’re crustaceans called amphipods. The vast majority of the members of this group are marine or fresh water dwellers, but there are a few that are terrestrial.

As their Down Under name implies, the land dwelling species move about by the spring action of their three pairs of hind legs, they hop. Because of their flattened body, they can manage to enter our homes through the gaps under doors.

Most of the time, the misguided animals wander into our air conditioned houses in the forlorn hope of finding moisture. Needless to say, the rarefied air in our modern homes lacks the water they seek. They die of dehydration and starvation relatively quickly.

Lawn shrimp range from 5 mm to 20 mm in length. Their color, while still alive, can range from pale brown to greenish to almost black. They often turn orange or red after they’ve died. Terrestrial amphipods need a moist environment to live. If it dries out, so do they and they die.

House hoppers are nocturnal living, for the most part, in the top 13 mm of the soil or mulch while feeding on dead organic material, breaking it down into fertilizer for your plants.

They can also be found congregating beneath wood piles, under trash cans, flower pots and other undisturbed objects. Because they lack the waxy coating on their exoskeleton that insects have, too much rain or too little moisture will often drive them by the thousands into our houses, onto our sidewalks and into our car ports.

Land shrimp can occur in numbers exceeding one million per hectare under the right conditions, but their presence poses no threat to humans, pets or vegetation. Few people will even notice them unless the amphipods are forced from their habitat by a heavy rain.

Even then, their accumulation is more of a nuisance and temporary distraction to the average homeowner. On rare occasions, house hoppers will enter ornamental ponds and swimming pools clogging water filters.

For the most part, controlling lawn shrimp isn’t necessary. But, if you feel the nuisance is just too great, most commercially available lawn pesticides will kill amphipods. To keep them from getting inside your home, seal the thresholds of outside doors.

Tim Lockley, a specialist in entomology, is retired from a 30-year career as a research scientist for the U.S. Department of Agriculture. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.

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