Lawn shrimp (Arcitalitrus sylvaticus) are terrestrial amphipods and scavengers usually found living under stones or decaying vegetation. They don’t have a waxy layer of protection over their bodies as do insects. That means that they lose or gain moisture easily from the environment. If they lose too much water, they will desiccate and if they gain too much water, that is also lethal.
These small pests are usually about ½ inch long, are pinkish/brown in color and have a “shrimp-like” form. They have two pairs of antennas, two eyes and they have leg-like appendages. Lawn shrimp are sometimes misidentified as springtails. The way you can tell the difference is that springtails have six legs and only one pair of antennae.
When they are migrating out of rain soaked areas, they are trying to keep from dying from too much moisture. The ones that do escape from moisture, die quickly in the drier environment inside. Dead lawn shrimp can be safely swept or vacuumed up and discarded. There is no need to treat with insecticides.
During rainy weather, you may also find large numbers of these “bugs” in swimming pools and they may even clog pool filters.