Published online by Cambridge University Press: 14 August 2009
Insects (Superclass Hexapoda) are arguably the most diverse and successful of all groups of animals. It is estimated that 20 million species could be living today (Jarzembowski & Ross, 1993) but only about 1.4 million have been described. They occupy all main environments except for those that are fully marine, and they have evolved many different feeding and defence strategies (Gullan & Cranston, 1994). Insects are susceptible to climate change, particularly temperature changes, and many are dependant on the plants on which they feed.
The fossil record of insects is based predominantly on their occurrence in non-marine (lacustrine and fluvial) sediments. They are usually preserved as isolated wings or rarely as complete insects. The wings of different groups of insects have a distinct venation which provides characters to enable their identification and classification. The Cretaceous and Tertiary insect record is supplemented by their remarkable preservation in amber.
The richness of the fossil record of insects has only begun to be realized in the last few years with the publication of three main databases. Two of these are of insect families that occur in the fossil record (Ross & Jarzembowski, 1993: updated in Jarzembowski & Ross, 1996; Labandeira, 1995). The third is a database of genera (Carpenter, 1992), although unfortunately this only contains data up to the end of 1983 and it is now out of date. Since 1983, an additional 500 families and roughly 1 000 genera have been recorded as fossils.