The microbats constitute the suborder Microchiroptera within the order Chiroptera (bats). They are most often referred to by their scientific name. Other English names are "insectivorous bats", "echolocating bats", "small bats" or "true bats". All these names are somewhat inaccurate, because not all microbats feed on insects, and some of them are larger than small megabats.
The distinctions between microbats and megabats are:
Most microbats feed on insects. Some of the larger species hunt birds, lizards, frogs or even fish. Microbats that feed on the blood of large mammals (vampire bats) exist in the Americas south of the United States. Microbats are 4 to 16 cm long. Many species have chitinase enzymes in their intestines that are produced by symbiotic bacteria. These help in digesting the insect prey.
Bats are one of the most famous examples for echolocation among animals. All microbats use echolocation. The only megabat which is known to echolocate is the genus Rousettus, which uses a different method of echolocation than that used by microbats. The echolocation system of bats is often called biosonar.
Microbats generate ultrasound via the larynx and emit the sound through the nose or the open mouth. Microbat range in frequency from 14,000 to over 100,000 hertz, well beyond the range of the human ear (typical human hearing range is considered to be from 20Hz to 20,000 Hz). The emitted vocalizations form a broad beam of sound that is used to probe the environment. See the main article on animal echolocation for details.
Some moths have developed a protection against bats. They are able to hear the bat's ultrasounds and flee as soon as they notice these sounds, or stop beating their wings for a period of time to deprive the bat of the characteristic echo signature of moving wings which it may home in on. To counteract this, the bat may cease producing the ultrasound bursts as it nears its prey, and can thus avoid detection.