It has long been believed that at the very least some insects can hear. Chef attention has been offered to those that make distinctive sound (e.g., katydids, crickets, and also cicadas) because it was normally assumed that these insects develop signals for interaction purposes. Organs perfect for hearing have actually been discovered in insects in ~ various locations on the thorax and also abdomen and, in one team (mosquitoes), top top the head.

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Among the countless orders that insects, hear is known to exist in only a few: Orthoptera (crickets, grasshoppers, katydids), Homoptera (cicadas), Heteroptera (bugs), Lepidoptera (butterflies and also moths), and also Diptera (flies). In the Orthoptera, ears are present, and also the capability to awareness sounds has been well established. The ear of katydids and also crickets are found on the very first walking legs; those the grasshoppers are on the first segment of the abdomen. Cicadas are noted for the intensity of sound produced by some species and for the elaborate advancement of the ears, which are located on the first segment of the abdomen. The waterboatman, a heteropteran, is a small aquatic insect through an ear top top the very first segment that the thorax. Moths have straightforward ears the are situated in certain varieties on the posterior component of the thorax and in rather on the an initial segment of the abdomen. Among the Diptera, just mosquitoes are known to own ears; they are located on the head together a component of the antennae.

All the insects just mentioned have actually a pair the organs for which over there is good evidence of hear function. Other structures of simpler kind that often have been considered to be sound receptors take place widely within this insect groups and in others. Over there is strong evidence that some type of hearing exists in two various other insect orders: the Coleoptera (beetles) and also the Hymenoptera (ants, bees, and also wasps). In this orders, however, receptive organs have actually not yet been positively identified.

Types the insect auditory structures

Four structures discovered in insects have actually been taken into consideration as perhaps serving an listening function: hair sensilla, antennae, cercal organs, and also tympanal organs.

Hair sensilla

Many specialized structures top top the bodies of insects it seems ~ to have a sensory function. Amongst these room hair sensilla, each of which is composed of a hair through a base part containing a nerve supply. Because the hairs have actually been viewed to vibrate in response to tones of details frequencies, it has actually been argued that they are sound receptors. That seems an ext likely, however, that the sensilla generally mediate the feeling of touch and also that their solution to sound waves is only incidental to the function.

Antennae and also antennal organs

Many sensory functions have been attributed to the antennae of insects, and also it is believed that they offer both together tactual and also as smell receptors. In part species, the advancement of intricate antennal plumes and also brushlike terminations has led come the pointer that they additionally serve because that hearing. This suggestion is sustained by positive proof only in the case of the mosquito, especially the male, in which the basic of the antenna is an increased sac containing a big number that sensory units recognized as scolophores. These structures, uncovered in plenty of places in the body of insects, commonly occur throughout joints or body segments, wherein they more than likely serve together mechanoreceptors because that movement. When the scolophores are connected with any kind of structure that is collection in activity by sound, however, the arrangement is the of a sound receptor.


In the simple structure the the scolophore, 4 cells (base cell, ganglion cell, sheath cell, and also terminal cell), along with an extracellular body referred to as a cap, constitute a chain. Expanding outward native the ganglion cell is the cilium, a hairlike forecast that, since of the position, acts together a trigger in an answer to any type of relative motion in between the 2 ends of the chain. The sheath cell v its scolopale provides support and also protection because that the delicate cilium. Two varieties of enclosing cells (fibrous cells and cells the Schwann) surround the ganglion and sheath cells. The ganglion cell has both a sensory and also a neural function; it sends forth its very own fibre (axon) the connects come the main nervous system.

In the mosquito ear the scolophores are connected to the antenna and are engendered by vibrations that the antennal shaft. Since the obelisk vibrates in response to the oscillating waiting particles, this ear is the the velocity type. That is an alleged that stimulation is greatest when the antenna is pointed toward the sound source, thereby allowing the insect to determine the direction that sounds. The masculine mosquito, sensitive only to the vibration frequencies that the hum do by the wings of the female in his very own species, flies in the direction of the sound and also finds the female because that mating. Because that the male yellow heat mosquito, the most effective (i.e., apparently best heard) frequency has been found to it is in 384 hertz, or cycles every second, which is in the center of the frequency range of the hum the females the this species. The antennae the insects other than the mosquito and also its relatives probably do not serve a true auditory function.

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Cercal organs

The cercal organ, i m sorry is discovered at the posterior finish of the abdomen in together insects as cockroaches and crickets, consists of a thick brush of numerous hundred well hairs. As soon as an electrode is placed on the nerve tribe of the organ, which has actually a rich nerve supply, a discharge of impulses can be detected once the brush is exposed come sound. Sensitivity extends over a reasonably wide variety of vibration frequencies, from listed below 100 to perhaps as high as 3,000 hertz. Together observed in the cockroach, the responses come sound waves up to 400 hertz have the exact same frequency as that that the stimulus. Back the cercal organ is report to be extremely sensitive, an accurate measurements continue to be to be lugged out. That is possible, nevertheless, that this structure, which is another example of a velocity form of sound receptor, is primarily auditory in function.