Sensillum
A sensillum is an arthropod sensory organ protruding from the cuticle of exoskeleton, or sometimes lying within or beneath it. Sensilla appear as small hairs or pegs over an individual's body. Inside each sensilla there are two to three sensory neurons. These neurons, or receptors, gather information about environment the arthropod is in:
Most sensillum are specially shaped according to the type of information they are gathering.Chemoreceptors
Chemo-reception is one of the most dominant senses in the insect kingdom. Many arthropods use chemical signals to locate food, shelter and mates.
Other invertebrates have similar sensory organs also referred to as sensilla; these consist of various papillae or ciliated areas of the cuticle connected to sensory neurones and occur in velvet worms, tardigrades and leechs.
