When Dead Dinosaurs and Bone-Eating Beetles Meet

May 08, 2008

Once upon a time during the Jurassic, a Camptosaurus dinosaur dropped dead in what is now Medicine Bow, Wyoming. The cause of death remains unknown, but it laid down for its final rest before the following, as told by Brigham Young University geologist Brooks Britt, happened:

"While flying low over a floodplain 148 million years ago, adult dermestid beetles used their antennae to detect the odor or decay and honed in on a decaying carcass.  Flying upwind they arrive at the carcass where the beetles mate (note – the adults have wings and can fly – the larvae lack wings and scurry about on six stubby legs)."

Close-up of a dermestid beetle (all insect photos provided by Brooks Britt)

"The eggs are deposited on the carcass.  The eggs that are not consumed by other insects hatch.  These minuscule larvae feed voraciously on wet, juicy tissues – their preferred food source.  Most larvae, however, are attacked and eaten by predatory beetles and wasps.  To help avoid predation, the larvae avoid light, and remain at depth in the carcass or hidden under the drying tent of the dinosaur's skin.  Aside from their mandibles, their primary protection is their long, multispiked guard hairs."

The beetle guard hairs

"Larvae that survive are subjected to mite infestations.  When the dermestid larvae attain their full size, they rapidly scurry away from the insect laden carcass.  To pupate in or near the carcass would mean almost certain death at the jaws of a predatory beetle or wasp.  At a safe distance from the carcass, the larvae burrow into wood or ground to pupate and later become flying adults.  The wood near the carcass may have been riddled with pupation burrows and chambers."

The dino victim
   

"When the carcass was nearly consumed, most of the other insects that were competing for the putrid flesh mature and depart.  At this stage, in the absence of most competitors and predators, the dermestid larvae are the most numerous necrophagous (corpse-eating) insects.  As the final bits of soft tissues are consumed, the remaining larvae struggle to obtain sufficient nutrients. They are tied to the carcass – it is impossible for them to go for a hike looking for another carcass.  If they pupate too early, they will die prior to emergence, or they will emerge as imperfect adults.  In the warmth of the Jurassic sun, the bones begin to ooze fats.  Some larvae, using their strong, paired mandibles, each armed with two teeth, bore a series of shallow pits probing for a meal.  But the hard, laminar of the bone yields insufficient nutrients.  They probe the bone, boring pit after pit, and each is abandoned.  The larvae lucky enough to probe near the ends of the bone find and consume the remaining cartilage or ligaments.  Beneath the cartilage, they strike a feast of tissue-laden bone, which they mine off, a fraction of a millimeter at a time. Finally, after days of mining, some larvae break though into the marrow-filled interior of the bones, where they feast on fats until they attain sufficient size to scurry off and pupate."

The feaster