Dipteran Larvae

Fossilized larvae of dipteran insects are found at several localities and in different levels of the Green River Formation, locally being “so abundant that they make glossy dark-brown layers or partings between the thin beds of rock” (Bradley, 1931; p. 12). Bradley (1931) illustrates Green River larvae belonging to at least 5 distinct dipteran families. Various types of flies have a larval stage that can be much longer than the adult stage. These larvae are often aquatic, and can feed on algae, plant material, decaying matter in the sediment, or be predatory. Dipteran larvae like the ones in this specimen are elongated, with hints of segmentation and poorly developed head, and lack segmented thoracis legs. Dipteran larvae are soft-bodied, with a flexible and poorly sclerotized chitinous cuticle. Therefore, their excellent preservation is another impressive example of the unique taphonomic conditions documented by fossils of the Green River Formation.

Reference:

Bradley, W.H., 1931. Origin and microfossils of the oil shale of the Green River Formation of Colorado and Utah. US Government Printing Office, USGS Professional paper 168, 58 p. doi:10.3133/pp168.