As Halloween approaches and thoughts turn to vampires and things that go bump in the night, it's fascinating to explore the real-world blood feeders that remind of the incredible diversity of life and the fascinating adaptations that have evolved in nature. Some can transmit diseases and require appropriate precautions, but all are remarkable examples of natural selection at work, each playing their own unique role in the web of life.

Here's a list of some blood-feeding specialists. 

Mosquitoes are the most well-known of blood-feeding insects. The females are the ones that take blood meals. With the protein they obtain from human blood, they develop eggs, said Dawn Gouge, a medical entomology professor at the University of Arizona Cooperative Extension. With the chemical scents of humans and the carbon-dioxide plumes that they exhale, mosquitoes follow humans and puncture the human skin. Their saliva has anticoagulants and anesthetizing chemicals so that humans don't feel mosquito bites until later, Gouge said. 

"If you think about blood in itself, it's an incredible protein rich substance," Gouge said. 

Bed bugs are small, oval-shaped insects that feed exclusively on blood, primarily during nighttime hours. These resilient creatures can survive for months without feeding, thanks to their remarkable metabolic adaptations. They use an elongated beak to pierce the skin and withdraw blood, often leaving characteristic lined patterns of bites on their hosts. Their ability to hide in small crevices and multiply quickly has made them highly successful in urban environments.

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Ticks are not insects. They belong to arachnids that have segmented bodies divided into two parts. Humans can get Lyme disease from the bite of the tick that carries Borrelia bacteria. Untreated Lyme disease can cause symptoms such as fever, rash, facial paralysis, irregular heartbeat and arthritis. 

"Their mouth part is like a harpoon that slowly pushes into you – it can release various chemicals to make it not hurt as much as you think it would," said Kathleen Walker, associate professor in the Department of Entomology in the College of Agriculture, Life and Environmental Sciences. 

Unlike mosquitoes that bite and leave after sucking blood, ticks hang on, suck blood and also drool out. That's how they can transmit things. People notice a tick because they notice a foreign object stuck to them, not because it's painful, Walker said. 

For those concerned about ticks, Walker emphasized prevention over panic. The main way to have protection from ticks is to protect pet dogs from ticks. Medications or tick collars that are recommended by veterinarians can be used. 

"When we go out hiking, we should always check ourselves, because there are other ticks besides the dog tick," Walker said. 

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Vampire bats are particularly fascinating as the only mammals that feed exclusively on blood. They use sharp incisors to make small, precise cuts in their prey's skin and then lap up the blood that flows. Their saliva contains powerful anticoagulants, and they display social behaviors such as sharing blood meals with hungry roost mates.

Many bat species, including vampire bats, can carry rabies and transmit the disease to humans. Less than 1% of bats carry rabies. That said, bats that act strangely or contact humans are 10 times more likely to be sick with rabies. 

Body and head lice are tiny parasitic insects that have evolved to live either on the human scalp or in clothing. They feed multiple times daily and, while they cannot jump or fly, spread efficiently through direct contact between hosts. Different subspecies have adapted to prefer different areas of the human body, with head lice specialized for gripping hair shafts and body lice adapted to living in clothing seams.

Fleas, unlike lice, are remarkable jumpers that feed on blood through specialized piercing-sucking mouthparts. The cat flea is the species most encountered by humans. The agile insects have laterally compressed bodies that allow them to move easily through hair and fur, while their powerful legs enable them to jump impressive distances relative to their size.