The sensory organ of insects is called the sensilla. These specialized cells are capable of detecting a variety of sensory stimuli and are located beneath the cuticle – the hard outer covering of insects.
Among the possibilities are:
Mechanical stimuli can be caused by the environment, the insect’s interaction with the environment, or the internal workings of the insect. It includes touch, position, gravity, etc. Three examples are:
- Tactile Mechanoreception – Accomplished via the trichoid sensilla which deforms when receiving stimuli and sends an electrochemical signal.
- Proprioception – This is the ability to sense the body’s relative position in relation to its surroundings. This can be accomplished by hair beds or setae, stretch receptors, and the campaniform sensillum.
- Sound Perception – Waves of air pressure cause movement of an organ used in hearing.
Some insects are able to detect infrared radiation. This allows some species of beetle to locate forest fires which provide them with burned wood critical for their mating ritual. They are able to do so by using infrared sensors located underneath their wings to absorb heat, which through a poorly understood process converts this IR heat into a mechanoreceptive signal.
Two types of chemoreceptors are found in insects: gustatory and olfactory sensors. Gustatory sensors can be considered “taste” sensors and are located in the mouths and on the legs of insects. Olfactory is to be considered “smell” and is found on insect antennae and certain parts of the mouth.
These chemoreceptors are further categorized into uniporous and multiporous.
Most insects possess a compound eye, which consists of a varying number of units called ommatidia. The number of ommatidia can be anywhere from a few to tens of thousands. Compound eyes allow a very large visual field and also let the insect focus on objects near and far away simultaneously.
In addition to compound eyes, insects often also have dorsal ocelli and stemmata.