Why the world needs Dung Beetles

To celebrate National Insect Week 2016 we thought we would introduce you to the custodians of the Hope Entomology Collection here at the Museum. Our insect collection is made up of a whopping 6 million specimens, so our resident entomologists definitely have their work cut out. However, they have taken a little time out to tell us all about their specialisms and why their favourite insects are the best.

Darren Mann – Head of Life Collections

Darren out in the field collecting Dung Beetles

Dung beetles have been my passion since my late teens. I started with British species and then gradually broadened my interests to encompass the world fauna. But why dung beetles?

Well, they are beautiful insects, exhibiting an array of shapes and colours; they have been around since the dinosaurs, and have interesting biologies and behaviours, from nest-building and parental care, to stargazing. As a group, dung beetles are also very important in the ecosystem, removing dung and recycling nutrients.

Not only that, but dung removal and relocation offers additional ‘ecosystem services’ of fly control, livestock parasite suppression, plant growth enhancement, improved soil structure, reduction of greenhouse gas emissions, seed dispersal, and pollination. Inevitably, they are a source of food for other animals too.

Darren takes a closer look at a collected specimen

Dung beetles are found in all regions of the world, and consist of three main groups: the dor or earth-boring beetles (Family Geotrupidae) of around 600 species; the ‘lesser’ dung beetles (Family Scarabaeidae, subfamily Aphodiinae) of around 3,500 species; and the ‘true’ dung beetles (Family Scarabaeidae, Subfamily Scarabaeinae) of around 6,000 species.

With just over 10,000 species in total you’d think we have found all the dung beetles out there, but not so: it’s estimated that 40 per cent of species new to science are still to be discovered. In the UK we have just 60 species and over half of these are in decline due to agricultural intensification, pollution, use of veterinary drugs, and changes in livestock farming practises. The Dung Beetle Mapping UK Project (DUMP) aims to highlight the importance of this group and promote research and conservation in this area.

Despite their name, not all dung beetles eat dung, with some species preferring fallen fruit, fungi, or even dead animals. The South American roller (Deltochilum valgum) is an avid predator of millipedes and another South American species (Zonocopris gibbicollis) feeds on snail mucus!

So with their high diversity, fascinating ecology, and great economic benefit, perhaps the question really should be ‘why not study dung beetles?’.

Mustachioed Robber Flies

To celebrate National Insect Week 2016 we thought we would introduce you to the custodians of the Hope Entomology Collection here at the Museum. Our insect collection is made up of a whopping 6 million specimens, so our resident entomologists definitely have their work cut out. However, they have taken a little time out to tell us all about their specialisms and why their favourite insects are the best.

Zoë Simmons – Life Collections

Zoe

I have many favourites in the collections that I look after- insects demonstrate an immense diversity of form and behaviour. So much so in fact that I defy anyone that says that there is not one thing that they do not find interesting among the almost one million species described to date.

One of the groups that I often find myself returning to though is the Asilidae or Robber Flies. This is a group of predatory flies that feed on a wide range of insect species. Many species sport heavily bristled moustaches, which are thought to protect their faces as they feed but have the added bonus of making the on-trend hipster insect of the moment.

Mustachioed Robber Fly
A ‘moustachioed’ Hornet Robber Fly in the wild

As is common with predators they have exceedingly good eyesight and will sit, perched until they spot movement, at which point they will strike at the prey item in the air.

The legs are furnished with long spines that help hold the prey and the mouthparts have evolved into a hardened beak-like structure which can stab through even the tough exoskeleton of beetles. Entomologists who specialise in catching Asilids have to be wary as these flies are not afraid to use this to their advantage.

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As it happens, the largest and most striking species of fly in Britain is the Hornet Robber Fly, or as it is more commonly known, Asilus crabroniformis. Superficially, its appearance closely resembles that of a hornet. Seen from a distance it is easy to see how the two species may be confused by the casual observer (pro-tip: look for the antennae. Hornets have long, obvious yellow-brown antennae whereas those of the Robber Fly are dark and small), so much so in fact that the species name for the Robber Fly crabroniformis, translates as ‘hornet-form’. This mimicry of a species that is able to sting affords the Robber Fly a level of protection. It does not have a sting itself but the bluff works well.

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Also of interest, and linked to the next post by Darren Mann, is the fact that this species is one of the top predators of dung beetles. The females require dung from a herbivore such as a horse or cow to lay their eggs in. As a consequence adults can often be found hanging out in fields near to piles of dung, hoping to meet the mustachioed mate(s) of their dreams, whilst snacking on dung beetles that fly in to start their own dung-related romance story. The presence of this Robber Fly species is often indicative of the quality of the dung and its associated beetle fauna, and as such should be greeted with warmth and a hearty ‘hurrah’ if spotted for it means that the habitat is healthy.