Why study learning in insects? What can it contribute to a general knowledge of how learning takes place in a wide variety of animals? There are many potential answers to these questions. This review will focus on the general contribution that can be made to systematic understanding of how learning has evolved and is controlled in a wide variety of vertebrate and invertebrate species. Any systematic study must begin with a well-defined phylogenetic lineage. Insects are in the phylum Arthropoda, which contains animals that have jointed exoskeletons (e.g., insects, ticks, crabs, lobsters, spiders). With at least 2 million extant species (some estimates range as high as 30 to 50 million), the arthropod class Insecta comprises the most diverse group of multicellular organisms (Borror, Triplehorn, and Johnson, 1989). Insects have adapted to a wide array of living conditions, ranging from most terrestrial to many aquatic environments. The diverse insect species...