An introduction to Quaternary Entomology

"One may not doubt that somehow, good
Shall come of water and of mud"
"Heaven" by R.C. Brooke (1913)

Beetles are the most diverse group of organisms on earth today. Despite this success they are geologically young, first fossils appear in the Cretaceous and only in the following Cainozoic the group experiences a rapid diversification and radiation. During the last 2 million years of the Quaternary beetles remained relatively stable and didn't experience significant changes or extinction events.
The study of fossil remains of beetles in Quaternary sediments provided both for geology as for biology interesting results.
The fossils provided insights into modern faunas, development as species longevity and population dynamics. In geology beetles are well suited to study the palaeoenvironment of quaternary sediments - their body is highly sclerotized and parts of the exoskeleton can be preserved in organic deposits.

Fig.1. The most sclerotized parts of beetles, like head, thorax and the cover wings (elytra) have the greatest prospect to become preserved in sediments (from BUCKLAND 2000).

Early research on fossil insects of the ice ages was carried out mostly not by professional entomologists, but by geologists, archaeologists or naturalists. This caused a proliferation of new described species with evocative names as Helophorus pleistocenicus (LOMNICKI 1894), Olophrum interglacialie (MJÖBERG 1904) or Lathrobium antiquatum (SCUDDER 1900).
Modern work by entomologists revealed in most cases that the supposedly extinct species are identifiable as modern ones, for example from five Helophorus species described in the early 19th century in the Pleistocene sediments of the Borislav site (Ukraine) as new, today no one remains, and all the specimens were collocated in four extant species.
In 1877 Samuel H. Scudder, entomologist and palaeontologist at the U.S. Geological Survey, published a first paper about fossil insects from the Late Quaternary deposits at Scarborough (Ontario) - he will subsequently dedicate the next 20 years of his life to the research of such remains all over North America.
Scudder following the tradition of the time was a very prolific species seeker, he described more than 1.144 insect species, however already in his lifetime he was criticised for many of these nominations, especially the use of very fragmentary or bad preserved specimen as immortalized in the name he gave to some of them, like Bembidion fragmentum.

Fig.2. Fossil beetles identified by Scudder from the Scarborough Formation, illustrated by Henry Blake in Scudder (1900). (A) Bembidion expletum, (B) Badister antecursor, (C) Pterostichus depletus, (D) Patrobus decessus, (E) Bembidion damnosum, and (F) Patrobus frigidus (from ELIAS 2010).

It was the Swedish entomologist Carl H. Lindroth (1905-1979) who reformed the field of paleoentomology.
By studying taphonomic processes affecting the preservation of insects and by establishing the most useful taxonomic characters, as for example the cuticular microsculpture (microscopic lines and meshes covering the surface of the exoskeleton), he introduced a serious taxonomic comparison between fossil and extant species, clarifying that most beetle species survived unaltered the last 2 million years.

The first work to use insect species to reconstruct a paleoenvironment was carried out by STROBEL & PIGORNI in 1864 on an archaeological site in northern Italy, many other paleontological studies followed in the next decades in Europe.

Fig.3. A tiny fragment of chitin emerging in situ from turf, found in the sediments of a former pond in the central Alps.

In 1955 the English geologist Russell Coope began to study the Upton Warren site near Birmingham (U.K.), searching for fossil mammal bones. The sediments were extraordinary rich of shiny, small fragments of chitin and insect bodies, so Coope tried to delve into this to him completely unknown subject. Patiently he compared the recovered remains with the collection of bugs hosted in the Natural history collections of Birmingham.
Coope was one of the first to compare fossils to recent species, without assuming from the beginning that all Pleistocene insects are extinct species. He published his results of the site of Upton Warren and others in 1959 and 1961.
Today his output counts more than 200 papers, even after retirement he continues his research and his contributions in paleoentomology provided the establishment, diffusion and acceptance of Quaternary entomology in the scientific community and geologists from the 1970 onwards.

Bibliography:

BUCKLAND, P. (2000): An introduction to Palaeoentomology in Archaeology and The BUGS Database Management System. Institutionen för arkeologi och samiska studier, Umea universitet: 62
ELIAS, S.A. (ed.) (2010): Advances in Quaternary Entomology. Developments in Quaternary Science 12: 288
SCUDDER, S.H. (1900): Canadian fossil insects. Geological Survey of Canada, Publication No. 710, Contributions to Canadian Palaeontology 2 (2):67-92
STROBEL, P. & PIGORNI, L. (1864): Le terremare e le palafitte del Parmense, seconda relazione. Atti della Societa italiana di Scienze Naturali, Milano 7: 36-37