Over 1.3 million insect species have been described, more than two-thirds all of known species. Some insect species date back to around 400 million years ago. They have many kinds of interactions with humans and other forms of life on Earth.
Plate from Transactions of the Entomological Society, 1848.
Early entomological works associated with the naming and classification of species followed the practice of maintaining cabinets of curiosity, predominantly in Europe. This collecting fashion led to the formation of natural history societies, exhibitions of private collections, and journals for recording communications and the documentation of new species. Many of the collectors tended to be from the aristocracy and it spawned off a trade involving collectors around the world and traders. This has been called the "era of heroic entomology." William Kirby is widely considered as the father of entomology in England. In collaboration with William Spence, he published a definitive entomological encyclopedia, Introduction to Entomology, regarded as the subject's foundational text. He also helped to found the Royal Entomological Society in London in 1833, one of the earliest such societies in the world; earlier antecedents, such as the Aurelian society date back to the 1740s. In the late 19th century, the growth of agriculture, and colonial trade, spawned off the "era of economic entomology" which created the professional entomologist associated with the rise of the university and training in the field of biology.
Most insects can easily be recognized to order such as Hymenoptera (bees, wasps, and ants) or Coleoptera (beetles). However, insects other than Lepidoptera (butterflies and moths) are typically identifiable to genus or species only through the use of Identification keys and Monographs. Because the class Insecta contains a very large number of species (over 330,000 species of beetles alone) and the characteristics separating them are unfamiliar, and often subtle (or invisible without a microscope), this is often very difficult even for a specialist. This has led to the development of automated species identification systems targeted on insects, for example, Daisy, ABIS, SPIDA and Draw-wing.
In pest control
In 1994, the Entomological Society of America launched a new professional certification program for the pest control industry called the Associate Certified Entomologist (ACE). To qualify as a "true entomologist" an individual would normally require an advanced degree, with most entomologists pursuing a PhD. While not true entomologists in the traditional sense, individuals who attain the ACE certification may be referred to as ACEs or Associate Certified Entomologists.
Example of a collection barcode on a pinned beetle specimen
Many entomologists specialize in a single order or even a family of insects, and a number of these subspecialties are given their own informal names, typically (but not always) derived from the scientific name of the group:
^Elias, Scott A. (2014). "A Brief History of the Changing Occupations and Demographics of Coleopterists from the 18th Through the 20th Century". Journal of the History of Biology. 47 (2): 213-242. JSTOR43863376.
"Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name. No man can be truly called an entomologist, sir; the subject is too vast for any single human intelligence to grasp."
Chiang, H.C. and G. C. Jahn 1996. Entomology in the Cambodia-IRRI-Australia Project. (in Chinese) Chinese Entomol. Soc. Newsltr. (Taiwan) 3: 9-11.
Davidson, E. 2006. Big Fleas Have Little Fleas: How Discoveries of Invertebrate Diseases Are Advancing Modern Science University of Arizona Press, Tucson, 208 pages, ISBN0-8165-2544-7.
Cedric Gillot: Entomology. Second Edition, Plenum Press, New York, NY / London 1995, ISBN0-306-44967-6.
Triplehorn, Charles A. and Norman F. Johnson (2005-05-19). Borror and DeLong's Introduction to the Study of Insects, 7th edition, Thomas Brooks/Cole. ISBN0-03-096835-6. -- a classic textbook in North America.