Wasps Populated Rotting Dinosaur Eggs
(Side view of egg cocoons and fractured dinosaur egg shell. Credit: Jorge Genise)
Jorge Genise of the Argentine Museum of Natural Sciences and colleague Laura Sarzetti came to that conclusion after finding exceptionally well-preserved fossils of insect cocoons in a broken, 70-million-year-old titanosaur egg.
Several eggs for this huge sauropod were found, but the broken one contained tiny, sausage-shaped structures that were about 1-inch long and .4 inches wide. These were later determined to be cocoons, most similar in size and shape to cocoons created by wasps.
The researchers wrote, "The wasps may have been attracted to the egg because of the presence of scavenging insects feeding on the decaying organic matter, or they may have been attracted to spiders feeding on the scavenging insects. In either scenario, after attacking the insects or spiders inside the sand infillings of the egg, the wasp larvae produced the cocoons described herein."
Using a bit of CSI-type investigating, Genise and Sarzetti discovered that the big 8-inch dinosaur egg was broken by force. Subsequent fractures permitted scavengers to feast on the egg's impressively sized yolk. Still other creatures arrived later, to feed on the scavengers.
The scientists concluded, "The presence of wasps, which are at the top of the scavenging food webs, suggests that a complex community of invertebrates would have developed around rotten dinosaur eggs."
This might seem like a problem for dinosaurs, but such carrion communities helped to clean up decaying material in advance of new nesting seasons. It's believed that many dinosaurs revisited the same nest sites year after year, so the gorging scavengers kept everything clean, readying nests for the next clutch of eggs.