La Brea Insects

3. Impression of small beetle (top) and millipede (bottom)
4.Beetle elytra with purple pigment, as seen when first exposed. The color fades in a few minutes when exposed to air.
Photo: http://www.tarpits.org/blog/2013/09/23

The tar pits at La Brea are best known for bones of large prehistoric vertebrates that were preserved when large animals wandered into the area, died and sank below the tar. Less well known are the fossil invertebrates. The PAGE Museum publishes a list of La Brea invertebrate fossils. The most numerous group is the insects and the most numerous insects are beetles. This is expected since insects are almost 60 percent of all described species and beetles are the most numerous group of insects.

However, beetles are over represented among the recovered fossils. Beetles trapped in the tar have a higher probability of being preserved than other insects. Beetles have thick hardened forewings called elytra that survive in the thick viscous tar. Other insect groups have wings that are thinner and more delicate. Fully developed wings do not contain cells. The cells that form the wings excrete the wing cuticle and structures, and retreat from the fully formed adult wing. The insect wing has no living cells to die decompose and disrupt the structure. Thus wings are the most common type of insect fossil and beetle wings, being more substantial are the most common insect fossil in the tar.

For more pictures of fossil insects and other fossils check out the Page Museum website.