Different kinds of true bugs can be very different sizes. The smallest are only a few millimeters long. The largest, the cicadas, can sometimes be 50 millimeters long.
True bugs have lots of different shapes. They may have long or short antennae having four or five segments. Their legs are adapted for grasping or for walking, and sometimes for swimming. Some can fly, some have lost their wings. Many true bugs have scent glands on the sides of the thorax. These glands make stinky chemicals that repel predators.
The mouth parts of true bugs have evolved into a long thin beak. They only eat liquid foods. The beak extends back between the legs to rest against the underside of the bug, and they swing it down and forward for use during feeding. The beak is made up of thin blades that are sharp at the end, and have a segmented cover. There are two channels in the beak, one spitting out saliva to keep the food flowing, and one for sucking in liquid food. Some true bugs can give a painful bite.
Adult true bugs have two pairs of wings, except for a few groups that have evolved to lose their wings. In one big group of true bugs, the front pair of wings are partly leathery, partly clear.
In most true bug species, males and females look similar.
There are over 82,000 species of true bugs, including about 134 families, and they are found all around the world. Nobody knows exactly how many species there are in Michigan, but it is at least 2,000.
True bugs are found in nearly all land and freshwater habitats, except very coldest. The only group of insects that have evolved to live on the ocean are true bugs. True bug groups are most diverse and abundant in habitats on land that are moist and have a lot of plant life.
True bugs go through a simple metamorphosis. After they hatch, the young bugs look very much like their parents, but they don't have wings. They grow and shed their skin five times. After the last time they shed, they have wings and are mature and can reproduce. They don't grow any more. In cold climates like Michigan, some true bug species survive the winter in the egg stage, some in the adult stage.
Some true bugs, like aphids, have more complicated life cycles, where females can give birth without mating during the summer, and then at the end of the summer, produce offspring that mate and go to another plant to spend the winter. In the spring their offspring go back to the original kind of plant and start the cycle again.
Most species live for a year or less.
Some true bugs are active in the daytime, others hunt at night, it varies by species. Most true bugs are solitary and don't come together except to mate, but some species live in groups. They don't interact very much, they seem to stay together just for protection (the group-living species usually have strong chemical defense which is probably even stronger when a whole bunch release their chemicals together).
The larger true bugs don't travel far, they tend to live in the place where they are born. Some of the aquatic bugs live in ponds that dry up though, and they will fly to new ponds. Some of the very small true bugs, like aphids, get blown on the wind and can travel very far that way.
Like all insects, true bugs use scent and touch to communicate. They may also use their vision, but many species can't see very well. Many true bugs use sound and vibrations to communicate. The cicadas are one group of true bugs that are famous for the sounds they make. They gather in large numbers and form choruses, where thousands of insects call from one place. Their smaller relatives also communicate to each other. They don't have the special sound-producting organ that cicadas do. Instead they drum their bodies on branches and twigs.
Some species of true bugs are mimics, they pretend to be ants, and sneak into ant nests to eat ant larvae.
True bugs take liquid food from plants or animals. Some suck plant sap, others dissolve seeds, some sip out the juice from cells in the leaves. Many true bugs are predators, stabbing their prey (usually other insects, sometimes other animals including vertebrates, like mammals and birds, snails, or spiders) and sucking out their blood or body fluids. For example, stink bugs feed on caterpillars and some aquatic bugs feed on mosquito larvae. Bed bugs are a parasitic member of the true bug group -- the feed on mammal blood, including humans.
Since true bugs are so diverse and so common, they have many predators.
Different true bugs have different defenses against predators. Most true bugs have camouflage colors so predators can't see them easily. Many have glands that produce chemicals that smell or taste bad. This repels predators. If they have strong chemical defense, they may have warning colors instead of camouflage. A few true bugs mimic other more dangerous insects, like ants or wasps. Some of the predatory true bugs can bite. Adult true bugs will fly away if they can.
True Bugs are consumers. Some are herbivores, some are predators, some are parasites.
Some species of true bugs feed on the blood of mammals, including people. Bed bugs are true bugs. One group of species in Central and South America carry a dangerous disease from one person to another. The bites and droppings of other species cause skin irritations.
Many plant-sucking bugs cause damage to crops and landscaping. For example aphids are major pests of many food plants.
A few true bug species keep harmful insects under control. In addition, gall-producing true bugs are potentially useful in controlling particular weed species.
Some true bugs include blood-sucking bed bugs, kissing bugs, assassin bugs, ambush bugs, stink bugs, chinch bugs, backswimmers, water boatmen, and marsh treaders. Aphids, cicadas, leafhoppers, planthoppers and scale insects are also in this large group.