Insect Hearing Evolution

When insects first took to land around 400 million years ago, they were presumably deaf (Gopfert & Hennig, 2015). Since then, hearing in insects has evolved independently no less

than 19 times throughout their evolutionary history. Only a relatively small number of insect species can hear, but within that group, “ear” form and location is highly varied (Yager, 1999).

Uses and Advantages of Hearing in Insects:

• Insects use their hearing to help them detect and avoid predators and for intraspecies communication, including the act of attracting a mate by acoustic signaling. Insects have hearing that is sensitive at high frequencies and over a broad frequency range, but these specifications are evolutionarily “tuned” to the range of frequencies that best allow the insect to hear their predator and communicate within their species. Most insects have two widely-spaced ears which aid the insect in determining the direction of sound. Additionally, some parasitoid insects listen to the singing of other insects to locate hosts for their parasitic offspring (Yager, 1999).

Location of Hearing Organs:

• For evolutionary reasons to be discussed later, the location of hearing organs in insects is highly varied. Ears are often located on the legs, mesothorax, metathorax, various segments of the abdomen, wings, mouth parts, and, most commonly, the caudal thorax or rostral abdomen (Yager, 1999).

Method of Hearing:

• Two different types of ears exist within insects: the tympanal ear, a pressure receiver, and the antennal ear, a particle velocity detector.

Evolutionary Driving Factors

• The need for communication, a skill that first appeared around 165 million years ago (Gopfert & Hennig, 2015).

• The need to evade predation by detecting predators. Most prominently, this refers to the detection of bats which use echolocation to locate their prey. Bat predation dates back to around 65 million years ago (Gopfert & Hennig, 2015).

Evolutionary Overview: