The world is filled with insects of all shapes, sizes, and colors. Some of them are, dare we say, “cute”—think ladybugs and butterflies. Others, like the ones on this list, are the unsavory characters of the pest world. What’s the creepiest insect on this list?

1. Japanese giant hornets

We live in comfort knowing that most insects are fairly small, but Japanese giant hornets can grow up to three inches in length. They are native to Japan and found throughout the country, including just outside Tokyo.

These hornets are more than just size. Their stings are lethal and contain more acetylcholine—the neurotransmitter that causes pain—than any other stinging insect. One enzyme in the venom is powerful enough to melt human tissue. The venom also contains a pheromone that attracts other hornets to sting you further, and unlike your average honey bee, these hornets can sting repeatedly.

2. Tsetse fly

Native to Africa, the tsetse fly feeds on the blood of vertebrate animals, but they leave more than itchy bites. In the process of feeding on blood, tsetse flies acquire and transmit small, single-celled parasites called trypanosomes.

Being infected by trypanosomes leads to the disease trypanosomiasis. In humans, this manifests as a red skin sore, fever, aching muscles, headaches, irritability, and swollen lymph glands. The disease eventually hits the central nervous system where it affects your personality, circadian rhythms, and speech and causes confusion, seizures, and hampered motor functions. The disruption of sleep cycle gained this disease the nickname the sleeping disease. If left untreated, this can eventually lead to death. Tsetse flies account for up to 300,000 deaths a year in Africa.

3. Triatomine

Alternately known as kissing bugs or assassin bugs, triatomine bugs are bloodsuckers that prey on wild animals and humans. They measure between half and three-quarters of an inch long and are black and dark brown in color. Their bites can cause some swelling and itchiness, but the real danger is Chagas disease.

Chagas disease isn’t spread by the bite but by the insect’s droppings, which can potentially fall into the bite. The disease is characterized by an intense fever, swelling of the face and body, and nervous system disorders. Over time, the disease can lead to some serious chronic issues, including heart disease and malformation of the intestines. If untreated, Chagas disease is fatal.

4. Fire ants

Found in nests of sand or soil, fire ants build surprisingly large mounds. They feed primarily on plant material and small insects. However, a fire ant sting is quite painful, causing a burning sensation and immediate swelling. Although you can easily survive one or two stings, a swarm of biting fire ants can be deadly. Aside from that, fire ants cause millions of dollars in crop damage each year.

5. Mosquito

The mosquito is annoying as is thanks to itchy bites and its tendency to ruin summer barbecues, but mosquitoes can prove to be highly dangerous thanks to their ability to carry blood-borne diseases. The anopheles mosquito is the biggest culprit, capable of spreading the deadly disease known as malaria. Malaria causes fever, chills, and flu-like symptoms. Severe forms of malaria involve cerebral and neurological symptoms. This leads to 219 million cases of malaria and 660,000 deaths a year.