Athayde Tonhasca suggests that there is more to the sexton beetle Nicrophorus vespilloides than meets the eye.
If you go for a stroll in the woods now and then, you may have come across a dead bird or small mammal. You may have paused to brood over life and mortality. However, that carcass was the end of the line of one life, but by no means the end of the line of life. To us, dead animals (and dung as well, for that matter), are things to be shunned. But we need to keep in mind that these are valuable resources, comprising complex proteins, carbohydrates, fats and sugars. And sexton beetles (also known as burying beetles), have evolved to exploit the life opportunities from a corpse.
Shortly after an animal expires, its body starts releasing the scents of decay. Thanks to their sensitive antennae, sexton beetles such as Nicrophorus vespilloides, a widespread species in Britain, can locate a corpse within an hour of death and from as far away as two miles.
After arriving at a carcass, a male-female pair of beetles examines it to assess its size; bodies that are too big to handle are rejected. If the ground is unsuitable, they drag the body to a better location. Using their heads, the beetles loosen the soil and gradually shove it aside, constructing a burial chamber that eventually sinks the carcass into the ground, a process that may take up to 8 hours. After burial, the beetles strip away any fur or feathers and shape the flesh into a compact ball, dousing it with secretions that act as anti-bacterial agents to slow down decomposition. The female then lays her eggs in the soil nearby.
Watch footage of sexton beetles in action at
BBC videos and National Geographic videos
After hatching, the life of a new sexton beetle becomes particularly interesting. Until they are about three days old, the young beg for food by pressing against the adult’s jaws, which stimulates regurgitation – a behaviour normally associated with birds and their nestlings. Afterwards the larvae feed directly on the carcass, but they are cared for by their parents throughout the entire time they are growing. This is a rare and highly developed behaviour in insects, normally found only in the social bees, wasps, ants and termites. Not only that, males and females increase their brood-care behaviour to compensate for the loss of a mate. The life of a sexton beetle larva is not always rosy, though; if the adults sense that the brood is too big or the carcass is too small, some of the smaller larvae are eaten, so that the remaining ones will have a sufficient food supply.
These complex interactions between parents and offspring represent the highest degree of sociality among Coleoptera, and that is why sexton beetles are considered to have attained the level of ‘subsocial’ on the spectrum of social species. And recently, a new twist has been added to the intricate lives of these beetles.
Females choose to allocate their time and energy to their existing offspring while they are dependent on adults for feeding. Males however, may have other ideas because of sexual competition; given the chance, other males will copulate with the female, which induces the resident male to keep on trying to mate to guarantee his paternity of the offspring. This dilemma has been solved with a chemical solution: during early stages of larval growth, females release a compound called methyl geranate, which has anti-aphrodisiac properties, inhibiting the mating instinct of males.
So there you have it: sexton beetles have created the first anti-Viagra.
For more information on these intriguing beetles, see:
Beetle moms send a chemical signal: ‘Not tonight, honey’
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