Invasive animals and insects are defined by their ability to thrive and aggressively spread outside of its natural habitat. This can be especially true when it is introduced to a new environment. Such animals include mammals, birds and reptiles and insects such as ants, moths, mosquitoes and arachnids.
The first thing that often comes to mind when we think about and invasion, is the invasion of insects and small animals to a home. They can spread throughout the home and completely take it over, using the materials of the home as food, building their nests in available private spaces and can denigrate the home from the inside out.
Insects can also invade whole crops farmed for human consumption and profit. They use crops as a mass source of food for their mass of numbers. It has been known to wipe out millions of dollars of crops and cause a shortage of food. This is usually why farmers are so aggressive in using pesticides in their crops.
Trees can also fall victim to insects and invading animals. Certain species of insects like the Tree Borer, are especially harmful to trees. Like all invaders, they attack in hoards for food, stripping the trees of their protective bark and choking the nutrients the trees need.
Treating these infestations can be high in cost to both the economy and the wildlife. Humans have to pay sometimes billions of dollars to treat and prevent the area infected, we also have to pay higher prices on the effected crop. Animals that used the trees or forests for their home, now no longer have the stability of their surrounding and have to migrate to better land.