Arthropods You Often See Immediately After Heavy Rain And Why They Appear
|
Published: 2025-Nov-17
|
Heavy rainfall changes activity patterns for many arthropods, and people often notice unusual movement on driveways, patios, lawns, and even inside their homes within minutes to hours of a storm. We are not talking about long-term changes in arthropod community, but rather immediate movements of arthropods away from soil as a survival strategy. Below are four common arthropod groups that frequently emerge after rain and what their behavior means.
Earthworms
Earthworms breathe through their skin, so they rely on oxygen in the soil. After heavy rain, the soil becomes saturated and oxygen levels drop. As a result, earthworms rise to the surface to avoid suffocation. Many of them dry out or die in large numbers once they reach open ground, especially when the sun comes out. Birds quickly take advantage of this and feed on the exposed worms, especially on side walks. This is why lawns often show a sudden spike in bird activity after storms.
Ants
Ant colonies face major risks when their underground nests flood. Workers respond by moving larvae, pupae, and queen(s) to higher and drier areas. This relocation can cause sudden trails along walls, trees, and sidewalks. Some species show remarkable survival tactics. The red imported fire ant (Solenopsis invicta), for example, is known to form a floating “raft” made of interconnected workers, brood, and queens during floods. This raft can drift for long distances until the colony reaches dry land.
Termites
Termite activity often increases after a rain event which triggers swarming behavior in subterranean termites. Subterranean termites live and nest underground, but will come to the surface to feed on wood or to swarm and mate. Winged adults called swarmers (aka alates), fly out to disperse and mate. Homeowners may spot them near windows, doors, or outdoor lights. The presence of swarmers indoors can be a sign that a termite colony is active inside or immediately around the structure.
Crustaceans (lawn shrimps and sowbugs)
Certain small land-dwelling crustaceans, often called lawn shrimp (Arcitalitrus sylvaticus) or terrestrial amphipods, emerge in large numbers after rain. They thrive in moist leaf litter, but when the ground becomes saturated, they escape to drier surfaces like patios, sidewalks, and garage floors. Despite their name, they are not insects. They dry out rapidly and often die in piles once the weather clears, leaving homeowners puzzled by the sudden appearance of "pink shrimp"”" near their doorsteps.
Why these arthropods are more visible after rain
Most of the sightings come from stress caused by flooded soil or the opportunity rain provides for dispersal. Earthworms, ants, sowbugs and lawn shrimps primarily relocate to avoid suffocation, but termites use humidity as a signal to swarm. While the activity can look alarming, these events are normal and usually short-lived.
How to avoid insects and arthropods from entering homes after heavy rain
There is no way to fully stop the arthropods from leaving their homes inside soil. However, one can stop or significantly reduce the entry of these critters into homes by sealing entry points such as the space under doors or cracks on walls and around the window. Door sweeps can be very useful in keeping these pests out of the way.
