The question of whether wasps are invasive is complex. Wasps encompass tens of thousands of species, most native to their environments and playing significant ecological roles. However, some specific wasp species have become invasive in new regions, causing disruption to local ecologies and economies. This article clarifies what defines an invasive species and identifies those that fit this designation.
Understanding Invasive Species
An invasive species is defined as a non-native organism that, when introduced to a new environment, causes or is likely to cause harm to the economy, environment, or human health. Not all non-native species are invasive; many can thrive in new areas without causing negative impacts. The harmful characteristic distinguishes an invasive species from a merely introduced one. Such introductions often occur due to human activities, including global commerce and accidental transport.
New environments often lack natural predators, parasites, or diseases, allowing introduced species to establish breeding populations and proliferate rapidly. Invasive species can then outcompete native organisms for resources, disrupt food webs, or introduce new pathogens. This ecological disruption can reduce biodiversity.
The Diverse World of Wasps
The perception of wasps as universally aggressive pests is largely due to a misunderstanding of their ecological functions. Most of the approximately 33,000 known stinging wasp species are native to their habitats and perform beneficial services. These insects are diverse in appearance and behavior, ranging from solitary species to social colony dwellers. Most native wasps are predators that help regulate populations of other insects, including common garden and agricultural pests like caterpillars and aphids.
Wasps also contribute to pollination, visiting a variety of plants as they forage for nectar. While their pollination efforts might not be as widely recognized as those of bees, wasps are essential pollinators for certain plant species. Some species, known as parasitoid wasps, lay their eggs on or within other insects, with the developing larvae consuming the host. This natural pest control helps maintain ecological balance.
Identifying Invasive Wasp Species
Despite the beneficial roles of most wasps, several species have become invasive outside their native ranges. The European paper wasp (Polistes dominula) is native to southern Europe, North Africa, and temperate Asia. It was first detected in North America in the 1960s and has since spread across much of North America, New Zealand, and Australia. This medium-sized wasp is yellow and black, often nesting in protected cavities like wall spaces or under eaves. Its ability to emerge earlier in spring and monopolize resources may contribute to its success.
The German yellowjacket (Vespula germanica) is another invasive species, originating from Europe, Asia, and North Africa. This social wasp was introduced to Canada in the 1960s and the eastern United States in the 1970s, rapidly spreading to regions including California, New Zealand, and Australia. German yellowjackets are black and yellow, often nesting in structural cavities, and are known for their scavenging behavior, which brings them into frequent contact with humans.
The Asian giant hornet (Vespa mandarinia), now known as the northern giant hornet (NGH), is native to parts of Asia. This large hornet, up to 2 inches long, gained attention after its detection in North America in 2019. While its establishment in North America is not yet widespread, its presence is a concern due to its predatory nature, particularly towards honey bees. The yellow-legged hornet (Vespa velutina), native to southern Asia, has similarly invaded parts of Europe and preys on honey bees.
Impacts of Invasive Wasps
Invasive wasp species can have far-reaching negative consequences across various domains. Ecologically, invasive wasps compete with native species for food resources, such as nectar and honeydew, and can disrupt local food webs. For example, the European paper wasp is a generalist predator that competes with native predatory insects for prey, reducing native biodiversity. In New Zealand, invasive Vespula wasps have been observed to outcompete native bird species for food and prey on native invertebrates.
Economically, invasive wasps can cause significant damage, particularly to agriculture and beekeeping industries. Species like the German yellowjacket and the Asian giant hornet prey on honey bees, leading to losses for beekeepers. In New Zealand, invasive wasps have caused direct financial loss by robbing beehives and killing bees, costing beekeepers substantial amounts for hive replacement. These wasps can also become a nuisance around outdoor activities, affecting tourism and recreational areas.
Invasive wasps also pose public health concerns. Species like the European paper wasp and German yellowjacket are more aggressive than many native wasps, increasing stinging incidents. Increased human-wasp interactions can lead to painful stings, allergic reactions, and even secondary infections. The presence of large numbers of aggressive invasive wasps can deter people from enjoying outdoor spaces, impacting quality of life in affected areas.