Paleontology is the scientific study of life during prehistory. Among the study of paleontology are several subfields that deal with specific forms of life and specific geological eras. Paleoentomology is the study of ancient insects and the environments they lived in. Paleoentomologists use techniques and concepts from a wide range of scientific fields including geology, biochemistry, genetics, embryology, and bioinformatics to paint a picture of insect life in prehistoric eras and chart the evolution of insects throughout history.
How Do Paleoentomologists Study Prehistoric Insects?
Paleoentomologists primarily rely on insect fossils to study the life and history of bugs. Unlike dinosaurs and mammals, Insects lack bones so they don’t leave behind skeletons for scientists to dig up thousands of years later. So, paleoentomologists have to look at other kinds of insect remains. These remains not only tell us about individual insect species but also how insects have evolved over time and the characteristics of the environment during certain geological periods.
Most of what scientists know about ancient insect life is from insect specimens trapped in amber. Tree resins are very sticky, so it traps insects, mites, and small invertebrates. Over time the resin hardens and encases the insects, preserving them for future generations to find.
Most amber insect fossils come from the Carboniferous period, which was characterized by vast swamp forests. Insects contained in amber inclusions tell us important things about the relationship between insect evolution and the development of plant life. Amber fossils tell us that insects and terrestrial plants developed at about the same time, some 400 million years ago during the Ordovician period.
If you place your hand in wet cement you have essentially made an impression fossil. Impression fossils occur when an insect gets trapped in layers of sediment. Over time the insect’s biological remains decompose, leaving behind a “mold” of the insect in the sediment. This mold hardens into rock over time. Impressions are just molds and do not contain organic matter, but they can give important clues about the physiology and morphology of ancient insects.
Compressions occur when an insect or part of an insect is compressed in sedimentary rock. These organic materials are compressed over eons and retain their colors, so they are easily identifiable. Most insect remains found in compressions are chitin from beetle carapaces. Chitin is a very durable substance so it tends to last much longer than other organic materials. Most compression fossils date back to the Carboniferous period.
Mineral replications are the rarest type of insect fossil and offer the most detailed evidence of ancient insect life. Mineral replications occur when dissolved minerals fill in the space after organic material deteriorates. The result is a full 3-D mineralized copy of the insect. Mineral replications can give paleoentomologists a detailed morphology of ancient insects, which they use to chart out evolutionary lines. Mineral replications usually occur in places with water rich in mineral content.
Since mineral replications usually have a different chemical composition than the surrounding material, they are easier to remove. For example, acids will dissolve calcium-based limestone and leave behind the silicate replication intact.