The smallest animal in the world, which is also the smallest insect in the world (so far) is the Megaphragma caribea otherwise known as a fairyfly. It is a parasitic wasp that lives on the island of Guadalope and feeds off the eggs of other insects. Specimens have been found between 0.10 mm to 0.17 mm in length. If your eyesight isn’t what it once used to be, you could have this little guy thread your sewing needle for you. Want to know what is the biggest insect in the world?
Like many of the smallest/biggest questions that I have encountered, this question is more complicated than it first appears. The smallest animal in the world must have more than one cell according to many different definitions of the world animal, so although protozoa are considered by some to be an animal, they are only one cell in size, so they are out.
The smallest vertebrate animal in the world is the Paedocypris fish found in the dark, swampy waters of Sumatra. It lives in an environment that is only slightly less acidic than the human stomach. This species also has the distinction of being the smallest fish in the world.
Last, but certainly not least, the smallest mammal in the world is the Bumblebee Bat or the Etruscan Pygmy Shrew, depending upon who you ask. The bat measures between 2 and 3 centimeters in length. Like many of the coolest creatures on Earth, this bat is listed as Endangered by the IUCN. The shrew measures about 3.5 centimeters and weighs more, but of course, the status of smallest mammal really depends on the age and gender of the species in question.