Its exoskeleton.
Thorax
the thorax
the tympanum
their eyes
Abdomen
It is the tongue.
Insects have three body parts, Head, Thorax and Abdomen. I therefore believe Thorax is the correct answer to your question.
Skull bones protect your brain.
The heart is a common part of the body that is found in snakes and insects. Eyes are another common feature between insects and snakes.
The body part that insects have and cat fleas do not is wings. Fleas are wingless insects that feed on the blood of animals including cats.
skin
the nervous system