Description

Mollanidae sp. and Chironomus kirklandi

Pliocene

Rita Blanca Formation

Oldham County, TX USA.

5mm caddisfly larval case and 4mm Chironomid on 65mm slab.

Insect.

The Mollandidae is a family of caddisflies which are not classified among true flies.  They belong to their own order, Trichoptera and are actually more closely related to butterflies and moths.

One remarkable fact about the group is that the aquatic larvae of some families build protective cases for themselves out of sand grains, gravel, wood bits, and other debris (all cemented by silk they produce).  These cases can be quite ornate and are also portable.  Another remarkable fact is that these larval cases have survived as fossils dating back to the Jurassic.  There is even a report of a case from a Permian-age site.

Chironomus is a genus of non-biting midge (a tiny fly) that dates back at least to the Eocene as it is known from Middle Eocene-age Baltic amber.  It belongs to the Family Chironomidae which goes back much further in time to the Triassic.

Here is an association piece with two different orders of insects and two different preservation types.