Space Grant Consortium - University of Wisconsin - Green Bay

Various modes of fossilizations of insects are reviewed (Grimaldi and Engel, 2005). We
are interested the most i n the fossils that are pr eserved in chert, such as in the Rhynie
chert (from t he O ld R ed S andstone i n S cotland; P ragian; a bout 396 -407 millio n years
ago). The R hynie ch ert contains t he f ossil o f what i s b elieved t o b e t he o ldest i nsect
(Engel and Grimaldi, 2004). Chert is microcrystalline silica, SiO2. It is translucent and
provides good qua lity fossils, c omparable t o t hose i n a mber, but f rom a m uch ol der
period. The insects were trapped in ancient shallow pools created by hot springs which
then rapidly silicified. Similar to chert is the Tertiary onyx, which is also a form of silica.
In the initial stages of our project we attempted to silicify insects in the laboratory with
sodium silicate at room temperature. We believe that the chitin is a good candidate to
undergo silicification due to its hydroxyl groups that can both hydrogen-bond to the silica
and can be entombed inside the silica gel. D ue to the fact that proteins are also present
together with the chitin, the probability for silicification is increased, since proteins are
known t o i nduce pol ymerization of s ilicates to s ilica ge l. Below are s hown ou r
experiments.
Experimental
For experiments JB1-JB4B, beetles were collected in Shawano, WI on May 29, 2008, and
had originally been preserved in 70% EtOH. Before the experiments, the beetles were
removed from the alcohol and allowed to air dry for one week. At the time that
experiments JB1-JB4B were started (after the week of drying) there was still some
moisture remaining inside of the beetles--either due to water or residual alcohol.
JB1: 24. March. 2009
Phyllophaga anxia (adult); 0.41g. The beetle was placed in scintillation vial and 4 ml of
Na-Silicate w ere a dded. This v ial w as k ept ti ghtly sealed to prevent desiccation.
Initially the beetle floated in the milky, viscous fluid. A rubbery gel appeared after 48
hours. The gel w as milky and translucent. The beetle w as embedded i n gel, with the
dorsal s urface of t he be etle e xposed a bove t he surface of t he gel. A s mall a mount o f
clear, yellowish liquid was present above the gel. This liquid has pH of ~11. More liquid
was noticeable above the gel after 5 more days (7 days total). The gel became discolored
near th e to p ( slightly yellowish). S lightly mo re liq uid w as n oticeable o ver t he n ext 7
days (14 days total). Observations were carried out for another week (21 days total) but
no more changes were noted.
JB2: 24. March. 2009
Phyllophaga anxia (adult); 0.25g. The beetle was placed in a scintillation vial and 4 ml of
Na-Silicate w ere ad ded. The cap of t his vi al was ke pt l oosely s ecured t o allow for
desiccation. Initially the beetle floated in the milky, viscous fluid. After 22 hours, a fine
ring of whitish gel was observed on the side of the vial at the surface of the Na-Silicate.
This ring increased in thickness over the next 20 hours (42 hours total). The main mass
of the Na-Silicate was also noticeably thicker at this time, but still flowed. This increased
viscosity resembled that of our alcohol-gel experiments (Liesch and Kolb, 2007). By the
third day of observations, a gel had formed and the beetle was embedded in the gel, with
part of the beetle exposed. The gel was milky and translucent. A small amount of liquid
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