Can inflict a painful bite. The venom from their bite sometimes increases a victim's body temperature and blood pressure, causing severe sweating and nausea.

Bites over time can become intensely painful, causing fever, insomnia and deep, slow-healing open wounds. If left alone bites can become infected, causing skin tissue to die. Young children and the elderly are especially susceptible.

Some species, including the house centipede, are known to inflict a painful bite similar to a bee sting.

Cockroaches can contaminate food, make humans sick, as well as trigger asthma attacks. The dust created by cast-off cockroach skins, dead bodies and droppings can especially aggravate allergies in children and sensitive individuals.

Transmit the Hantavirus, which causes Hantavirus pulmonary syndrome (HPS). Hantavirus causes flu-like symptoms, and over one-third of cases lead to death. Currently there is no treatment or vaccine for HPS.

Can inflict painful stings and will sting repeatedly. Their sting contains toxic venom that causes blistering pustules and severe anaphylaxis or hypersensitivity. Serious fire ant attacks can produce thousands of stings and be deadly to both animals and humans.

Bites cause irritation, blood loss and itching. Some species can spread diseases such as bubonic plague and typhus. Other species of fleas can be intermediate carriers of tapeworms and can infect humans if accidentally ingested.

Spread diseases readily because they move quickly from rotting, disease-laden garbage to exposed human foods and utensils. In fact, more than 100 pathogens are associated with flies including salmonella, staphylococcus, e. coli and shigella. These pathogens can cause disease in humans and animals including typhoid fever, cholera, bacillary dysentery, hepatitis, ophthalmia, polio, tuberculosis and infantile diarrhea.

Bite is medically significant for humans. Most bites occur when the spider is accidentally crushed or squeezed. The spider's venom is strong enough to cause considerable local pain and may cause tissue death at and near the bite.

Inflict stings that if repeated can result in hypersensitivity in about two percent of the population. Africanized honeybees, also known as "killer bees," are an extremely aggressive subspecies of the European honeybee. They have been known to chase and sting people and pets for hundreds of yards. Deaths can also occur due to allergic reactions from the larger number of stings received.

Some species transmit viruses, such as the West Nile virus, causing encephalitis (swelling of the brain) resulting in seasonal epidemics in North America during summer and fall. Serious symptoms of West Nile disease can include high fever, headache, neck stiffness, muscle weakness, disorientation and paralysis. Mosquitoes have also been known to transmit infectious agents causing malaria, lymphatic filariasis, yellow fever and dengue fever.

Inflict painful stings that can cause swelling and become infected easily aggravating skin conditions and/or allergies. Some species aggressively defend their nest and will sting when disturbed.

Can carry and transmit a number of dangerous diseases including salmonella (food poisoning), murine typhus, hantavirus pulmonary syndrome, and rat-bite fever. They also contaminate food products, damage stored goods, and leave behind distinct droppings of excrement.

Inflict painful stings that may be fatal for those with allergies. Some scorpion bites can also be fatal to young children and the elderly.

Spread dangerous diseases. Ticks feed on blood and transmit diseases including Lyme disease, Colorado tick fever, Rocky Mountain spotted fever, babesiosis, relapsing fever and tularemia. In the United States, ticks cause more illnesses each year than mosquito-borne diseases.

Inflict painful stings that can cause swelling, become infected easily and aggravate skin conditions or allergies. Yellow jackets will defend their nest when disturbed and can release an attack pheromone to other nest mates, launching an aggressive attack on victims. Unlike the honeybee, which stings only once and then dies, a single yellow jacket can sting repeatedly.