Entomology is the branch of science that studies insects. It covers everything from how insects are built and how they behave to their role in spreading disease, pollinating crops, and shaping ecosystems. With roughly 1 million described insect species making up about half of all known life on Earth, entomology is one of the largest and most practical fields in biology.
What Entomology Covers
Entomology splits into two broad categories: basic and applied. Basic entomology focuses on understanding insects themselves, including their anatomy, physiology, genetics, behavior, ecology, and evolution. Applied entomology focuses on the ways insects affect human life, from agriculture and forestry to medicine and urban pest control.
Within basic entomology, several sub-disciplines tackle different questions. Insect taxonomy is the work of identifying, describing, and naming species, then organizing them into a classification system that reflects evolutionary history. Phylogenetics traces how different insect groups are related through shared ancestry. Biogeography maps where insects live and why, drawing on environmental and geological factors. Other specialists study insect cells and tissues under microscopes, or investigate how insect bodies carry out chemical and physiological processes.
What Entomologists Actually Do
Professional entomologists work in research labs, universities, government agencies, conservation organizations, and agricultural companies. Their daily work varies widely depending on their specialty, but common responsibilities include studying the roles insects play in ecosystems, researching insect physiology, developing strategies for controlling pests in agriculture and urban environments, studying insect genetics to understand adaptation, and educating the public about insects’ ecological importance.
Some entomologists spend most of their time in the field collecting specimens and observing behavior. Others work primarily in labs analyzing DNA, running experiments on insect development, or testing pest control methods. In medical settings, lab technicians work alongside entomologists and physicians to study insect-borne diseases, running tests and maintaining equipment used in diagnosing and preventing infections.
Medical Entomology and Disease
One of the highest-stakes branches of entomology deals with insects that transmit diseases to humans and animals. Malaria, dengue, yellow fever, and plague are all spread by insect vectors, and between the 17th and early 20th centuries, these diseases together caused more human death and illness than all other causes combined.
Medical entomologists study the transmission cycles of these diseases: how pathogens move between insects, humans, and animals, and what environmental conditions allow outbreaks to spread. This work has grown more urgent as insect-borne pathogens develop drug resistance and the insects themselves become increasingly resistant to insecticides. At the same time, the number of scientists trained in medical entomology and vector ecology has declined, creating a shortage of experts equipped to respond to emerging threats.
Agriculture and Pest Management
Entomologists are essential to protecting the world’s food supply. Insect pollination alone was valued at €153 billion globally in 2005, representing 9.5% of the total value of world agricultural food production. Research by INRA, CNRS, and UFZ scientists estimated that if pollinators disappeared entirely, the resulting loss to consumers would range from €190 to €310 billion.
On the pest control side, entomologists develop and refine Integrated Pest Management (IPM), a strategy that prioritizes prevention over chemical treatment. IPM programs start with correct identification of the pest species, which is critical for choosing the right control method and avoiding harm to beneficial insects. Entomologists set action thresholds, meaning specific population levels at which a pest becomes a genuine health hazard or economic threat. Only when those thresholds are exceeded do they recommend interventions, starting with the lowest-risk options like trapping, physical removal, or habitat modification before resorting to pesticides.
Forensic Entomology
Insects are reliable biological clocks at crime scenes. Forensic entomologists use the predictable life cycles of flies and other carrion-feeding insects to estimate how long a person has been dead. After the first 3 to 72 hours following death, fly eggs, larvae, and pupae become one of the most reliable tools for determining the age of remains.
The main techniques involve calculating accumulated degree hours (a measure of temperature exposure over time that controls insect development speed), consulting life history tables for specific species, and using species-specific growth curves. In later stages of decomposition, entomologists can also assess the succession patterns of different insect species arriving at remains in a predictable sequence, though this method is generally less precise.
Modern Tools in Insect Research
Two technologies are transforming how entomologists identify and track insects. DNA barcoding uses short, standardized genetic sequences to identify species. Compared with traditional identification based on physical features, molecular methods require less specialized knowledge of insect anatomy and have become widely accepted for confirming species identity. The tradeoff is that DNA barcoding requires laboratory equipment and is more expensive and time-consuming than visual identification.
Artificial intelligence and computer vision are closing that gap. Deep learning models trained on insect images can now perform rapid, automated species identification, which is especially valuable for fieldwork or for operators who lack expertise in morphological classification. Researchers are combining both approaches: using AI for fast initial identification and DNA barcoding to resolve cases where species look nearly identical. This combination is particularly useful in forensic entomology, where distinguishing between closely related fly species can make or break a time-of-death estimate.
How Many Insects Remain Undiscovered
Scientists have formally described roughly 950,000 insect species so far. Several independent analyses over the past three decades have converged on an estimate of about 6 million total insect species when undiscovered ones are included. But even that number may be conservative. A 2023 study in Systematic Biology found that for every insect species defined by physical appearance, there are on average about 3 additional “cryptic” species, genetically distinct populations that look identical under a microscope. Factoring in this hidden diversity, the researchers projected a possible total of over 21 million insect species.
That means somewhere between 85% and 95% of all insect species have never been formally described. This enormous gap is one reason entomology remains such an active field, and why citizen science programs have become valuable. The National Park Service’s Dragonfly Mercury Project, for example, has engaged over 4,500 volunteers across 107 parks, contributing more than 19,000 hours to collecting dragonfly larvae used as indicators of mercury contamination in aquatic ecosystems. Programs like these expand the reach of professional entomologists by putting trained eyes and hands in places researchers can’t always be.