No. 5 - Argentine Ants
Sometimes,
the grass is greener on the other side of the hill. Ants often relocate to new
regions, even new continents, where they find the conditions to be particularly
amenable. Such is the case with Argentine ants (Linepithema humile). Once
native to South America, these dark-bodied ants now live in vast colonies
across Europe, the United States
and Japan California
No. 4 - Fire Ants
Like Argentine ants, fire ants (Solenopsis invicta)came to the United States from South America, probably as stowaways on freighters and other ships. Since the 1930s, the aggressive ants have spread slowly but steadily across the U.S. Sun Belt. Today, fire ants occupy more than 330 million acres in 12 southern states and Puerto Rico, and there is evidence they've become established in California and New Mexico.
Fire ants organize themselves into two types of colonies. Single-queen, or monogyne, colonies have only one egg-laying queen and may contain as many as 100,000 to 240,000 workers. Multiple-queen, or polygyne, colonies can have as many as 60 egg-laying queens and 100,000 to 500,000 workers. Multiple-queen colonies won't fight with each other, so they often live in close proximity. As a result, some areas can have as many as 800 fire-ant mounds per acre.
If a person or animal disturbs one of these mounds, the ants swarm and attack aggressively, delivering painful, burning stings. Most attacks occur outside, but they can also occur in homes and health care facilities. In 1999, the Annals of Internal Medicine described two cases of fire-ant attacks in Mississippi nursing homes. Ants invaded the facilities, climbed from the floor to the patients' beds and delivered hundreds of stings. Both patients eventually died.
No. 3 - Africanized Honeybees
No social insect is more notorious than the Africanized honeybee, the so-called "killer bee" (Apis mellifera scutellata). It has earned this reputation, not because of its size or the potency of its venom, but because of its defensive nature. While European honeybees — the gentler version introduced to North America by European colonists in the 1600s and 1700s — defend their nests, they do so with just 10 or 20 individuals. Africanized honeybees mount much larger attacks, recruiting 1,000 bees or more to drive intruders away. A single attack can result in hundreds of stings, which can cause the deaths of pets, livestock and even people.
If a single assault squad is a thousand strong, what's the size of a colony? Like all members of the Apis genus, Africanized honeybees can have colonies with 50,000 to 70,000 insects. What makes them special, however, is how they run their colonies. Those of the African bee tend to grow faster, with one queen able to produce 1,500 eggs a day. But they rely on swarming — when a single colony splits into two — even more. African colonies commonly swarm more than 10 times a year versus their European counterparts, which may swarm only one to three times a year. This helps to explain why Apis mellifera scutellata has spread so rapidly since the 1950s, when African honeybees introduced to Brazil escaped into the wild and began their slow and steady spread through South America and into North America.
No. 2 - Yellow Jackets
Yellow jackets, wasps of the Vespula andDolichovespula genera, are familiar visitors to summer picnics and family cookouts throughout North America. They buzz near food and drinks, hoping for an easy meal. But the two or three yellow jackets we see on our soda cans are sure signs that others are lurking nearby. Some species locate their colonies underground, often in the abandoned burrows of rodents. Others build their basketball-sized nests in trees, barns or abandoned vehicles. Either way, colonies typically contain 15,000 workers and a single queen.
Unfortunately, population explosions of yellow jackets have become increasingly common, especially after warm winters or in areas, such as Hawaii, where temperatures remain higher throughout the year. In such conditions, scientists speculate, colonies may keep active workers all winter long and begin the breeding season with a head start. Some of these colonies may even have multiple queens, resulting in much larger nests supporting an unusually large number of individuals. In 2006, scientists discovered several of these super-sized yellow-jacket nests in the Southeast. One nest in South Carolina had 250,000 workers and 100 queens. Another filled the interior of an abandoned 1955 Chevrolet.
No. 1 - Mound-building Termites
Utter the word "termite" to a homeowner, and he or she will instantly fill with dread. In North America, this reaction is caused by the subterranean termite, a successful social insect that lives in colonies with thousands of hungry, wood-devouring animals. Just as spectacular are the mound-building termites (Macrotermes sp.) common to tropical Africa. These insects house their colonies in large, elaborately constructed mounds, some of which can last 20 years and weigh several tons. A colony's queen lives with her king deep inside the mound, cocooned in a royal cell tended to by thousands of workers and attendants.
The queen is a marvel of reproduction. She can lay 5,000 to 30,000 eggs a day, which will amount to some 200 million eggs over the course of her 20-year life. Colonies aren't this large, of course, because the mortality rates of workers and soldiers can be quite high. As a result, colonies typically contain 200,000 termites. That's still enough to wreak havoc. Mound-building termites eat the stems and roots of plants, often cutting the base of a plant at ground level. In certain regions of Africa, they are considered pests because they destroy important crops, such as barley, maize, wheat, millets and sorghum.