EXCEPTIONAL PRESERVATION OF FOSSIL INSECTS IN LACUSTRINE DEPOSITS

Insects represent the most species-rich group today and although they are often thought of as fairly fragile, they have an extensive fossil record that begins in the Early Devonian. All extant orders of insects, representing a range of morphologies and ecologies, are found preserved in the fossil record, and this is due to their preservation in lagerstätte deposits. Insect body fossils are found in several different types of depositional environments, but their preservation in amber and in lake sediments have proven to be most important – in terms of the temporal and geographic extent recorded, the diversity captured and the quality of preservation. By using datasets compiled from the fossil insect literature, conducting comparative studies within well-known lagerstätte, and by conducting actualistic studies in the field and in the lab, we now have a greater understanding of the processes that influence the preservation of insects in lacustrine environments. Although insects preserved in lacustrine deposits do not have the quality of preservation found in amber deposits, these compression fossils can be quite detailed and informative. In general, lacustrine environments preserve a primarily allochthonous assemblage with a bias towards those groups which are smaller and more robust. In addition, the type of lake and the region sampled within a lake can influence the quality and representation of fossil insect groups preserved. Examples of well-known North American lacustrine deposits will be reviewed to highlight common taphonomic processes and the important role that continental lagerstätte deposits play in our understanding of insect ecology and evolution.