Insect. ... Insect, (class Insecta or Hexapoda), any member of the largest class of the phylum Arthropoda, which is itself the largest of the animal phyla. Insects have segmented bodies, jointed legs, and external skeletons (exoskeletons).Insects all have a hard external covering made of something called chitin. Their bodies are made up of three sections called the head, the thorax, and abdomen. All insects will have a pair of antennae on their head. They all have six legs connected to the thorax (arachnids will have eight legs). Viewers can enjoy different activities of several types of insects in this video.