Over 50 percent of all living organisms are insects. Early fossils show flying insects lived as long as 300 million years ago during the Carboniferous Period. These small invertebrate animals, familiarity known as bugs, are six-legged creatures with segmented bodies. Some also posses one or two pairs of wings. Insects that live under rocks, on plants or around other animals are present in almost all ecosystems.

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Lift up a rock, and you may find some ants.

Woodlice

The Woodlice family of insects that live under rocks include "rolly-pollies," or bugs that roll into a tight ball to escape enemies. These flattened bugs with an armored shell-like body covering enjoy the damp environment under rocks because they breathe through gills. Woodlice are beneficial bugs for gardens, because they recycle dead plant matter into organic nutrients and return these to the soil. They're less welcomed by gardeners when large populations infest greenhouses and damage plants like immature ferns.

Ants

Ants are hard-working, social insects that live in colonies. Their presence in gardens is appreciated by homeowners who benefit from ant control of less desirable insects like termites. Worker ants, who make up the majority of a colony, leave chemical trails that help their co-workers to find sites with food. Some foraging ants travel as far as 200 meters away from their nests in one day. Fire ants, also known as red ants, build almost invisible nests under rocks. Their bites are very irritating to the skin and colonies are often eradicated when found in gardens, since multiple bites are dangerous to young children, small animals and those with weakened immune systems.

Beetles

Beetles are insects with strong jaws and hard, retractable covers to protect their wings. Types of beetles are found living under rocks in almost all areas of the world, except oceans and polar regions. The ladybird bug is a colorful spotted beetle that eats destructive garden insects like aphids and scale insects. One ladybird beetle eats an estimate 5,000 aphids during its lifetime. These red, orange or yellow insects with black spots hibernate under rocks during the cold winter months. Ladybirds escaping the harsh winter weather band together for warmth in groups of between 50 to 100 beetles.

Crickets

Crickets are long-legged jumping insects, related to grasshoppers. Male crickets seeking females to mate with make the a loud chirping call by rubbing their fore-wings together. Crickets live under rocks, as well as in burrows, and feed on fungi and decaying plant matter. Gardeners do not encourage crickets because they also eat young seedlings. Colonies of mating crickets are very loud and considered a noise nuisance by some homeowners. If you count the number of "chirps" in 15 seconds of their mating song, then add 37, the result gives you an approximation of the air temperature, expressed in degrees Fahrenheit.