Northern Georgia has been besieged by millions of giant arachnids called Joro spiders. These brightly coloured East Asian spiders have draped parts of more than 25 counties in the State with their thick webs. Porches, mail boxes and gardens have all been taken over by the spiders, prompting a flood of anxious social media posts by the residents.
Joro spiders are part of a group of spiders known as “orb weavers” common to China, Taiwan, Japan and Korea. They spin symmetrical circular webs and use their venom to immobile prey that get caught in their webs. The venom, however, poses no threat to human beings.
How did the Asian spiders end up in the U.S.? Scientists believe that the spiders hitch-hiked to Georgia through shipping containers. The spiders were first spotted here in 2014 and since then their population and range have expanded steadily across the state, but nothing prepared residents or researchers for the number of spiders they would face this year. Experts believe that the invasive species could spread even farther into other parts of the United States.
Invasive? What does that mean?
Invasive species are organisms that migrate to or are introduced to a new geographical location, where they pose a threat to the environment. They could be insects, plants, animals or pathogens. These species start to grow and multiply quickly in the absence of natural predators from their original homes.
How do invasive species spread?
- Some species arrive in a new area through migration.
- Some are spread unintentionally by human activities. When people travel they often inadvertently carry alien species along. For instance, insects may arrive in a new place by travelling on luggages.
- Some species are introduced on purpose as pets or to combat pests, which turn out to be invasive in the new place.
Why are they considered threats?
Invasive species cause harm to the ecosystem in many ways.
- In the absence of natural predators, a new and aggressive species can breed, spread quickly and overrun the local habitat. Native species may not have evolved defences against the invader, further boosting the invaders growth.
- The threats from an invasive species also include preying on native species and outcompeting them for resources, thereby restricting the growth of native species. Some invasive species are capable of changing the conditions in an ecosystem, such as the soil chemistry.
- Invasive species can change the food web in an ecosystem by destroying native food sources. People who depend on the ecosystem’s native resources will also be affected.
However, some scientists are optimistic that the Joro spiders, though invasive, could actually bring unexpected benefits. They could act as natural pest control as they kill off mosquitoes, biting flies and stink bugs that damage crops.
Picture Credit : Google
