What Bugged the Dinosaurs?: Insects, Disease, and Death in the Cretaceous

9. Sanitary Engineers of the Cretaceous

9. Sanitary Engineers of the Cretaceous On an alluvial flood plain near the amber forest, a large ornithopod dinosaur momentarily stopped grazing among the fern fronds, raised its tail, and defecated. Before the last of the waste even reached the ground, the air was crackling with the vibrating wings of thousands of dung beetles of all sizes and shapes. From large and round to small and oval, the beetles landed directly on or adjacent to the evacuated material. Not a moment was lost, and some began burrowing into the pile of waste even before the dinosaur had moved away. In order to get a head start, a few small brown females began laying their eggs immediately in the mound of partially digested plant material. Their robust cream-colored larvae would dwell in the dung heap for several days, hopefully developing fast enough to avoid predacious rove beetles and slender parasitic wasps that would eventually be searching for them, along with pecking birds, scratching lizards, and other vertebrate predators. A few dung beetle larvae ate some eggs of a parasitic nematode worm that had lived in the dinosaur’s intestine. The nematodes would remain inside the beetles for life but could only finish their life cycle if another dinosaur came along and gobbled down the infested insects. Some of the larger dung beetles were more protective of their progeny and after reaching the bottom of the pile, continued tunneling into the ground. No eggs were laid until the females packed the tunnels with dung fragments dragged in from above. The developing larvae would feed on these brood balls in relative safety since if the dung pile was broken apart by predators, the buried brood was hidden from view. Other beetles never entered the dung mass, but broke off and molded small portions into balls that could be rolled far away from the original source. Using massive jaws to clip away a small portion of dung from the original pile and their front legs to shape the prize into a ball, the beetles turned around and used the two back pairs of legs to push the sphere along the ground. A latecomer suddenly appeared and attempted to steal a ball away from one of the females. She viciously defended her future brood cell, grabbing the opponent with her mandibles and flipping it over. After successfully fending off several additional marauders, the exhausted female dug a hole into which she rolled her prize, deposited an egg on the fecal mass, and buried them together by refilling the hole. Soon mites and nematodes that had hitched rides on the adult beetles would begin multiplying in the remains and moving through and over the dung pile, encountering various stages of flies and beetles that were finishing their development and would provide transportation to yet another fecal deposit. A group of immature garudimimids, looking like horny-crowned cassowaries, moved out of the forest and onto the plain under the watchful eyes of their parents. When they encountered the ornithopod dung, they paused and began to scratch through the mass, using their hind legs, sending feces flying while pulling the pile apart. The strong claws at the end of each toe sliced through the soft fibrous material and exposed scurrying adult beetles and unwary grubs which they snatched up in their toothless beaks. After only a few minutes of feeding on the exposed plain, they rushed off to seek cover in a nearby patch of shrubs. Deep in the forest, an old, infirm dinosaur took a final breath and slowly sank to the ground, leaving his body to the whims of nature. In less than a minute, several large carrion flies that had detected death in the air landed on the still body and began depositing masses of eggs on the face, especially around the mouth opening. 80 – CHAPTER NINE Within the day, white legless maggots hatched from those eggs and began squirming into the mouth cavity, creating a hot, fetid environment that other insects couldn’t tolerate. Eventually, the wriggling larvae finished feeding and left the cadaver, crawling some distance away before burrowing into the soil to pupate. As the corpse dried, small brown beetles began feeding on the skin, dried flesh, and even on the surface of some of the bones. The eggs these oval insects laid hatched into minute larvae with long, stiff hairs that served both as camouflage and defense from predators on the lookout for insect prey. These beetle...