Insects have the most abundant species of all living things on the earth; they are typically adapted to various environments and have rich diversity.<br>The author noted the indicative characteristics of the fossil insects, and collected them at the following sites: Tomizawa site (Sendai City, Paleolithic to Kofun period), Matsukawado site group (Kasugai City of Aichi Pref., middle Jomon to Edo period), Asahi site (Kiyosu-cho and other three towns of Aichi Pref., middle and late Jomon to Medieval period) and Ikegaya site (Shizuoka City, end of Jomon to Heian period). In order to make use of restoring the paleoenvironment, these fossil insects were classified under a microscope and compared with present insect specimens. I succeeded in identifying a total of nearly 13, 000 of them from the four sites.<br>Many phytophagous beetles, such as Scarabaeidae and Limnobaris sp., and some aquatic beetles such as Dytiscidae were found at the Tomizawa Paleolithic site, indicating that at that time it was a shallow marshy area surrounded by woods. It is also assumed that the climate was colder than at the present, judging from the presence of northern species such as Ilybius poppiusi.<br>Aquatic and marshy insects were found in the water area, and terrestrial and phytophagous insects in the land area at the Tomizawa site, clearly confirming the supposed paleo-geographical features based upon the diatom analysis. Fossil insects were accumulated nearly at the same places where those insects were living.<br>At the Matsukawado site group, there were many forest-inhabiting insects in the peat layers of the middle Jomon period, indicating that the people lived surrounded by trees. It is assumed that the climate at that time was a little colder than of the present, judging from the presence of northern species such as Donacia ozensis. In the layers of the Kamakura period to the Edo period at the Matsukawado site group, there were a lot of phytophagous beetles such as Anomala rufocuprea, Anomala cuprea, Anomala sp. and Rutelinae. This shows that fruit trees and vegetable crops were planted by people around their residences.<br>Samples from the Asahi site of the middle Yayoi period were characterized by the existence of many coprophagous and ground-wandering insects gathering on filth. These urban insects indicate the possibility of the existence of breeding animals and the concentration of people in the Asahi moated circular settlement. It is thought that the Asahi site was an artificical open space, where natural vegatation was cut down.<br>At the Ikegaya site, a number of paddy pests such as Donacia provosti and Scotinophara lurida were found in the deposits of the late Yayoi period to the beginning of the Kofun period and from the Heian periods. During these periods, paddy fields must have been commonly cultivated.