Land Hoppers from Australia

What bug is this?
Location: Sydney Australia
April 9, 2012 2:44 am
We found hundreds of these on the floor of our family room (all dead) next to two walls – from corner to corner.
Shiny gold/brown with a soft shell. Look like a giant flea.
Climate – warm. Fairly dry after 2 years of wet.
Signature: Mike of Epping

Dear Mike of Epping,
These terrestrial Crustaceans or Amphipods are native to Australia and they are known as Land Hoppers.  Most of our reports come from California and occasionally UK and Florida where the species has been introduced at the beginning of the twentieth century, or perhaps even earlier, most likely with the introduction of Australian plants that were imported to grow in foreign gardens.  In North America, Land Hoppers are known as House Hoppers or Lawn Shrimp.  They live and thrive in damp soil where they generally go unnoticed due to their drab coloration.  After heavy rains however, they often migrate in great numbers to drier areas like garages and homes where they promptly die and turn pink or red in color.  You may read more about Land Hoppers on the Victoria Museum website and on University of Florida IFAS website where their dampness requirements are explained as:  “Terrestrial amphipods live on the surface (top 1/2 inch) of mulch and moist ground. After rains, large numbers of amphipods can migrate into garages or under the doors of houses. There they soon die. Amphipods do not have a waxy layer on their exoskeleton as do insects. They lose or gain moisture from their environment. Too much of a water loss results in desiccation while too rapid a gain is also lethal. This is why they migrate out of rain-soaked soil to drier areas where they usually end up dying anyway. Most species are active at night.”