RSPB Trainee Ecologist Kirsty Godsman explores the parenting skills of insects after finding out some fascinating facts about carrion beetles.
Do insects make good parents?
Last month, I discovered something fascinating about a closely related group of species commonly known as the carrion beetles or Sexton beetles (all belonging to the genus, Nicrophorus). This is a group of beetles that anyone with a moth trap might be familiar with as they are attracted to light. But if you have never come across them before, here is a photograph of one of the 6 species that occur in the UK.
Nicrophorus vespilloides (www.eakringbirds.com)
At first glance, these beetles may seem a little gruesome. They are known as carrion beetles because they feed on carcases as adults and larvae. As a result of this association, they can be covered in mites and usually smell unpleasant. However, delve a little deeper into the lives of the carrion beetles and you might find yourself warming to them.
In order to find a mate, adult beetles must find the carcass of a small vertebrate. This can be a difficult task in itself as it is a very limited resource. Once a carcass has been located, they will then need to fight off any competitors. Once there is only one male and one female left, they remove the hair or feathers of the carcass and bury it in the ground. This is an incredible feat for something that is no bigger than 3cm. What is possibly even more amazing is that, if the ground is unsuitable for digging in to, they will drag the carcass to a more suitable substrate. They will also form a sphere or brood ball with the carcass, onto which they secrete a liquid which is thought to preserve it. The female then excavates a corridor from here where she will lay her eggs.
Then it gets really interesting.
At this point, the male and female wait for the eggs to hatch and continuously guard the nest from predators and competitors. Once the eggs hatch, the males of some species leave but the rest continue to guard their nest. The females begin provisioning the brood and will not leave until her offspring have left. Initially, the female has to lead the newly hatched larvae to the carcass by “chirping” or stridulating her wing-cases on her abdomen. She then must feed her young directly by regurgitating. It has been suggested that many species must do this after every larval moult or the young will never make it to adulthood.
Although the circumstances may seem grisly, this behaviour is far more sophisticated and complex than most people would expect from an insect. However, they are not the only insects to provision their offspring in some way. For example, the tiny pot beetles (Cryptocephalus species) build a case for each egg that they lay which prevents predation of their offspring. It is very common for herbivorous beetles such as leaf beetles and weevils to lay their eggs on the larval host plant so that, as soon as they hatch, the larvae are able to feed. Some weevils even go as far as to roll a leaf up to protect their eggs. The care provided by Nicrophorus mothers, however, is the most involved of any non-social insect.