Invertebrate zoology is the study of invertebrates—animals without a backbone—a remarkably diverse group that accounts for an astounding 97% of all named animal species, encompassing creatures from sponges and mollusks to arthropods and various worms. Due to this vast diversity, the field boasts numerous subdivisions, such as entomology (insects), arachnology (spiders), and malacology (mollusks).
The early modern period saw significant advancements, notably with Conrad Gessner's Historia animalium (1551-1587), which compiled existing and new observations on insect life. The invention of the microscope around 1599 revolutionized the field, allowing Robert Hooke to publish detailed illustrations of microscopic invertebrates in his groundbreaking Micrographia (1665). Further advancing scientific methods, Francesco Redi famously employed controlled experiments in the 17th century to disprove the long-held theory of spontaneous generation, demonstrating that flies did not spontaneously arise from rotting meat.