The burying beetle, Nicrophorus vespilloides, also known as the common sexton beetle, is a remarkable insect. Its unique life cycle and interactions with its environment make it an intriguing subject.
Introducing Nicrophorus Vespilloides
Nicrophorus vespilloides is a medium-sized beetle, measuring 1.2 to 2.0 centimeters. It has a flattened, squarish body with prominent orange-yellow and black markings on its wing cases, known as elytra. Its antennae are clubbed and entirely black, which helps distinguish it from similar species.
These beetles are widespread across temperate regions, inhabiting diverse environments such as forests, grasslands, and urban green spaces, as long as small vertebrate carcasses are available. The common name “sexton beetle” comes from the historical role of a church sexton, who cared for the churchyard, a fitting name for an insect that attends to the deceased in nature.
The Unique Burying Behavior and Its Ecological Role
A defining characteristic of Nicrophorus vespilloides is its carrion-burying behavior. Upon locating a small dead animal, such as a mouse or bird, which they detect from a distance, both male and female beetles work together to move the carcass. They prepare the carrion by removing fur or feathers and shaping it into a compact “brood ball.” This ball is then moved underground, often by digging out the soil beneath it, creating a secluded chamber.
The purpose of this burial is multifaceted. It safeguards the carrion from larger scavengers and protects it from rapid decomposition by other insects, particularly flies, which would compete for the resource. Parents also apply antimicrobial secretions and beneficial microbes from their gut to the carcass, which slows decay and prevents the growth of harmful bacteria and fungi. This creates a preserved, nutrient-rich food source for their developing offspring.
These beetles play an ecological role as natural decomposers. By burying and processing small carcasses, they prevent the accumulation of decaying organic matter. Their actions help return nutrients to the soil, facilitating the natural cycle of decomposition and nutrient flow within their habitats.
Remarkable Parental Care and Life Cycle
Nicrophorus vespilloides exhibits extensive parental care, a rare trait among insects. Both male and female parents are involved in caring for their young, a behavior known as biparental care. After the carcass is buried and prepared, the female lays her eggs in the surrounding soil near the brood ball.
Once the larvae hatch, they migrate to the prepared carcass. The parents feed their offspring by regurgitating predigested food, a process called oral trophallaxis. This direct provisioning ensures the larvae receive adequate nutrition, though larvae can also self-feed from the carcass. Parents also defend the brood ball from predators, competing insects, and microbes.
The life cycle continues as the larvae develop within this protected “nest,” feeding on the carrion. After about a week, when the larvae have completed development, they disperse from the carcass remnants and burrow into the soil to pupate. New adult beetles later emerge from the pupae.