The branch of zoology concerned with the study of insects.
With nearly an estimated 3 million species, insects account for approximately two-thirds of all known organisms. Because of this enormous amount of species in the Insecta class, even entomologists have difficulty identifying the differences, as those are often subtle or even invisible without the use of a microscope.
The Insecta class belongs to the phylum Arthropoda (animals that have an exo-skeleton), as do spiders, or Araneae, which are often mistakenly classified as insects but actually belong to the Arachnida class along with scorpions, ticks and mites. The same goes for millipedes and centipedes, earthworms and snails and slugs, who belong to the Myriapoda, Lumbricina and Gastropoda classes respectively.
The word consists of the Greek words entomos, meaning ‘insect’, and logos, meaning ‘study’ or ‘science’.
The Greek entomos and the Latin insectum both mean ‘divided’ or ‘cut in half’ – the affix sect- is also used in words like section and sector, both meaning ‘division’.
The word insectology does exist, although entomology is more widely used. Entomology originated in the 18th century, when specialists started using that name instead of the less elegantly sounding insectology. Moreover, the word insectology is a combination of Latin (insectum) and Greek (logos) roots, whereas the word entomology is entirely Greek. Insectology is recorded in the New Oxford Vol. I English Dictionary as a synonym for entomology.