This particular top 5 is not conceived based on which insect kills the most people, which carries the most venom, which is the most vicious, or which is the most brutal. Rather, the classification ranks these little buggers based on their overall nastiness and appeal (or lack thereof).
5. Soldier (Army) Ants
The insect Eciton burchellii is familiar to many, even if they don't remember it by name. Have you ever seen the documentaries on TV, showing a raft made out of living insects, crossing a river because why not? Those are soldier ants, whose soldiers reach as much as half an inch in length.
They are in the nasty habit of not building their own colony, which can be avoided by animals that want to live. They are constantly on the move, trotting on the forest floor in a thick column numbering in excess of one million individuals on occasion.
Now, what makes these ants worse than, say, other ants, is their utter disregard for anything in their path. There have been unconfirmed reports that they have even killed horses that were in their way as they were migrating. These ants tend to consider everything that moves a threat to them.
4. Africanized Honey Bee
At number four in our top, we have the Africanized honey bee (Apis mellifera scutellata), which was obtained by breeding honey bees from Europe and southern Africa, with the purpose of making their offspring capable of surviving in the jungle.
However, someone dropped the ball big time, releasing 26 queen bees of the new species in Brazil. Now they are spread throughout the Western Hemisphere, and no external clues separate it from the normal, European variety.
The differences become quickly visible when they chase any intruder that spends more than a second near their hives for about a quarter mile. What makes them especially dangerous is the fact that they swarm easily, and also that their colonies number in the tens of thousands of individuals.
3. Japanese Hornet
The third spot in our classification is occupied by everybody's friend, the 1.62-inch (4-centimeter) long, venom-spitting Japanese Hornet, known among scientists as Vespa mandarinia japonica. Its best recommendation is this YouTube video
These insects are not particularly violent by nature, in the sense that they would tolerate quite a lot before taking action. However, when they do, there is a high probability that what upset them will no longer be alive within a few hours.
When they sting and release their multi-toxin venom, they also release a pheromone that calls all other Japanese Hornets in the vicinity to take part in the action. Suffice it to say that an enzyme in their venom can dissolve tissue, and that another chemical attacks the nervous system.
2. Tsetse Fly
The reason why the tsetse fly made it to the second position in this top is that it's responsible for the deaths of between 250,000 and 300,000 people every year. This little bugger mastered the art of infecting humans and other animals with trypanosomiases, also known as sleeping sickness.
Currently, it lives in an area of Africa that is inhabited by more than 60 million people. Access to treatment is scarce, and this, too, accounts for the high number of casualties it produces. The insect only feeds on vertebrate blood.
In order to control tsetse fly populations, some projects even sought to capture males, irradiate them, and then release them back into their colonies. But these efforts proved to be insufficient, even if infection rates have decreased slightly over the past couple of years.
1. Bot fly
The “winner” in this top is not an especially vicious insect per se. The thing that really makes it a nasty piece of work is that it puts its larva inside animals. Of the 150 species in the family Oestridae, one is specialized for putting its larvae inside humans.
There are videos showing how a bot fly larva living in a human host looks like, but none will be linked here, out of sheer humanity and compassion for those who fell prey to the fly. Suffice it to say, the larvae constantly eat as they grow immediately under the skin.
The good part about infected people is that they tend to figure this out sooner rather than later, and extract the flesh-eating demon out of whatever part of their bodies the larvae were attached to. In some cases, however, when the larvae grow in the brain, there isn't really that much anyone can do.