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Submodule 4: Invasive Insects
Introduction
Insect introductions into the U.S. have increased rapidly over the past century, largely because of increased trade and travel. Early in the 1820s, most of the insects introduced into this country were beetles buried in soil brought from Europe. This soil was used as ballast for empty ships that, once in the U.S., offloaded the soil and replaced it with freight to be shipped back across the Atlantic. Fire ants (Solenopsis invicta) are thought to have entered the U.S. from South America in the same way. Based on these and other examples, it appears that most introductions of detrimental invasive insects occurred unintentionally. Researchers speculate that the large fraction of insects introduced into the U.S. from Europe became invasive and established because the climates are similar between the two continents.
Since insects are sometimes released into the wild in an attempt to initiate biological control over invasive plants, some data have been collected on the success of introduced insects in a new environment. Still, researchers have little explanation for why some insects are successful in establishing a population in a new environment while others are not. There is some speculation that the size of the initial invading population is a factor in that a large initial population increases the chances of successful establishment.
Invading insects can sometimes cause a decrease in population or even extinction of native insects by out-competing them for resources such as food and habitat. For example, a native Florida wasp, Pseudhomalopoda prima, important for insect control, dangerously declined in numbers after the introduction of another wasp, Chrysomphalus aonidium, from Asia.
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