Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [73]
Biparental care, in which both parents cooperate to take care of the offspring, is at least as rare as male-only care among animals. It is seen in a few insects, however, including some that have the unfortunate attribute of being able to clear a room better than any other species. When I was doing my doctoral research at the University of Michigan Biological Station, the state-of-the-art Alfred H. Stockard Lakeside Laboratory had recently been completed. It was a lovely building, with excellent facilities for studying all kinds of local flora and fauna, from algae to woodpeckers. I was lucky enough to have a room to myself on the second floor, where I housed my crickets and recording equipment. Most days I worked happily at the microscope or with my experimental subjects, chatting with the other students and faculty, and generally having a grand time. But sometimes one of us would see David Sloan Wilson or one of his helpers walking toward the building with a white bucket, and we all knew to scatter. A multitalented evolutionary biologist, at the time Wilson was working on burying beetles, and the stench was enough to make paint peel.
As their name suggests, burying beetles locate recently dead animals by smell. If a male arrives at a carcass first, he sends out a chemical signal to attract a female. The pair then prepares the carcass as a nursery by stripping off any fur or feathers and shaping it into a ball. They cover their prize with specialized secretions that deter mold from growing (though this does nothing to deodorize the body, as we discovered to our regret). They then dig in the soil underneath the carcass, allowing it to sink into the forest floor. Once the carrion ball has been safely sequestered underground, the pair mates. The female then lays her eggs in the soil surrounding the carcass, and when the eggs hatch, the larvae beg for food from their parents by turning their heads toward mom or dad and waving their tiny arms. They are fed with either bits of carrion carved off the carcass like slices from a roast, or regurgitated meat that has been partially digested by a parent.
Although this lifestyle has much to recommend it (a steady and nourishing food supply, protection from predators once the carcass is buried), burying beetles face a daunting problem: finding a suitable dead animal, and once it is found, defending it against rivals. Even avid hikers and wilderness lovers rarely come across a dead animal at all, much less one that is both small enough to handle and still fresh enough to provide the right environment for raising young. The beetles have extraordinarily sensitive odor detectors on their antennae, and can sniff out a carcass from miles away, but even so it is an extremely difficult undertaking. Recently acquired carcasses are therefore highly sought after, and if a burying beetle comes across a carcass that has already been colonized by another individual, pitched battles may result. Both parents participate in defense of their property, and if the male happens to be away from the carcass when a male intruder threatens, the invading male will kill the offspring and mate with the female. Female intruders are not as successful in taking over a carcass. If both parents are present, they can usually fend off the invaders and hang onto their prize. It is thought that this advantage of pair defense is what led to the evolution of parental care by both the mother and the father in this insect group. If the carcass is large enough, multiple females may stay and lay their eggs, although one of them is generally dominant over the others.
Perhaps because of this difficulty in finding carcasses, one species of burying beetle has abandoned the role of "nature's undertakers," as one website refers to them, entirely. The substitute for dead birds and