There are almost 20,000 species of insects in Finland. Insects play an important role in the ecosystem of Finland because of the enormous numbers of individuals within this huge number of species. The many different adaptations of insects in their structure and physiology has allowed them to successfully get established in Finland. 

Most of the insects are plant eaters. Many insects are useful as they pollinate the flowers during the short summers to produce seeds. Some control the population of the pest insects which destroy plants. Bees are prized for their honey production. 

Almost 90% of the insect species belong to one of the following 4 insect orders viz., hymenoptera (ants, muurahaiset), diptera (flies, kaksisiipiset), coleoptera (beetles, kovakuoriaiset) and lepidoptera (butterflies, perhoset). 

Insects are diverse in shape but nevertheless there are some common features in them such as: - Three pairs of legs - Wings - Antennae - Compound eyes - Division of body into 3 parts: head, thorax and abdomen. There are of course exceptions to the above in some insects. Furthermore, insects differ from adults in their appearances during development (ontogeny). The life cycle of different kinds of insects differ in their phases of development . For example butterflies, beetles (Coleoptera, kovakuoriaiset), hymenopteron (Hymoneptera, pistiäiset) and dipterans (Diptera, kaksisiipiset) have a perfect metamorphosis which includes four totally different phases: egg, larva, pupa and adult. The different phases in ontogeny differ from each other not only in physical appearances, but also in the methods of nutrition. LINKS: 

http://www.varasto.uku.fi/departments/ecolensci/uh

http://cc.oulu.fi/~srytkone/srpage/insecta

http://www.uku.fi/~holopain/stt/sttnfrm.htm