Nature’s Recycling Squad – the role of dung beetles

Nesting by the Horned Dung Beetle (Copris lunaris): 1 – Initial stage, male (left) and female (right) working the ‘dung cake’; 2 – Female alone, making brood-balls of the ‘cake’ for laying eggs. Illustration by V.A. Timokhanov (Almaty, Kazakhstan).

Waste disposal is a growing problem for any industrialized nation. The UK alone generates about 100 million tonnes of waste each year, the majority of which is still being disposed of through landfill. The present story is about dung beetles or scarabs (family Scarabaeidae) that are involved in processing and decomposing dung.

On average, about 40% of the food intake of mammals is either excreted as urine or passed out of the body as faeces. This waste is decomposed and returned to the soil by insects that use dung as food for themselves and for their larvae, thereby preventing it from building up. How this is accomplished is best known for cattle dung.

A cow’s fresh dung pat is colonized by a succession of dung-breeding insects, numbering several dozen species and often exceeding 1000 individual insects. A total of 275 species has been reported to occur in cattle dung in Britain. The majority of them are dung beetles that feed directly on dung. There are three main ecological groups of dung beetles. First, small-sized beetles (Aphodius species) usually feed in the main dung mass. Others, like the horned dung beetle, dig burrows beneath the pat and pack pieces of dung into them for feeding their larvae (see figure above). The third group includes beetles that make spherical dung balls, roll them away and bury them intact in shallow burrows. The Sacred Scarab is the most famous of the rollers. As well as dung beetles, the pat is colonized by dung-feeding fly maggots, predatory beetles which feed on eggs and larvae of other insects, small parasitic wasps, fungus-eating insects and mites, etc. At the advanced stage of degradation, soil invertebrates, including earthworms, begin to move into the dung pat. The natural rate of dung degradation depends on temperature, humidity, habitat and season of deposition. In Britain, the complete natural disappearance of a dung pat is achieved in two to three months.

Sculpture of the Sacred Scarab in the Natural History Museum in Stokholm, Sweden. © Dmitri Logunov, Manchester Museum.

It is known that each cow produces an average of 12 dung pats per day, or over 9000 kg of solid waste per year. It is estimated that each year approximately 200 million tonnes of waste are produced by livestock in England and Wales, and about 900 million tonnes in the USA. About third of this is recycled by dung beetles. In the USA alone, the annual economic value of this service is at least $380 million.

Unfortunately, the activity of dung beetles is severely disrupted by current agricultural practices, such as the treatment of livestock with persistent anti-helminth drugs given to kill parasitic worms or helminths. Residues of these drugs can persist in the dung and are lethal to the beetles. As a result, the dung pats of animals treated with anti-helminthes remain biologically undegraded for months, fouling available grazing area. If left unprocessed, livestock wastes may present a health risk to humans, because they can contain some pathogenic microorganisms.

By recycling the nutrients locked up in dead organic materials such as dung, insects make these nutrients available to new life. As recyclers, they do an indispensable job for our planet. Without organisms breaking down dead organic materials and recycling nutrients in the wild, as well as in gardens and on farms, the planet would soon be piled deep with the waste products of its inhabitants, and potential spread of diseases would be unavoidable. Whether we like it or not, our own existence directly depends on insects and their ecological services. As M. Telfer (2004) put it: “Not everyone welcomes having ‘creepy-crawlies’ around but we should be grateful for what they do.”

In the following video, our special guest, Ms Roisin Stanbrook from the Manchester Metropolitan University, is taking about the ecological role of dung beetles in Kenya.

The presented story is based on: Logunov D.V. 2010. Nature’s recycling squad. Biological Sciences Review, 22(3): 22-25.

Further reading:

Berenbaum, M.R. (1995). Bugs in the system. Insects and their impact on human affairs. Helix Books.

Waldbauer, G. (2003). What good are bugs? Cambridge-London: Harvard University Press.

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A decade of invasion – a story of Harlequin Ladybird in the UK

The Manchester Museum’s collection of Harlequin Ladybirds recently acquired under the ongoing museum project ‘Thematic collecting’.

Recently, the Manchester Museum’s Entomology Department acquired some specimens of the Harlequin Ladybird, an invasive beetle species that appeared in Britain (Essex) in 2004 only, but is now a widespread and even dominant species of ladybirds in the UK.

 

Harlequin Ladybird – Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) – is a beetle species in the same family with the Seven-spot and Two-spot Ladybirds, both being considered gardener’s best friends as natural enemies of aphids and other garden pests. Harlequin Ladybird was deliberately introduced from east parts of Eurasia, where it is a native species, to many places of continental Europe as a biological agent to control aphids (=greenflies) and scale insects. As Harlequin Ladybird has excellent dispersal abilities (by means of flight), it was just the matter of time until it could have reached the British Isles.

A number of factors have contributed to the successful establishment and dominance of this ladybird species in the UK, particularly, its high reproductive capacity and ability to live in most available habitats. Harlequin Ladybird is also a voracious predator that can feed on other ladybird species.

The UK Ladybird Survey is a citizen science initiative that was launched in 2005, right after the first records of Harlequin Ladybird in Britain had been done. This programme is aimed at encouraging people across Britain to track the spread of Harlequin Ladybird (and other ladybirds) across the UK and submit their records online. Based on this survey, it is clear that by 2014 the Harlequin Ladybird has extended its range by almost half of the country. A decline of seven native ladybird species, which is correlated with the arrival of Harmonia axyridis, has also been demonstrated.

How to control this species and its spread in the UK is a bit unclear. Harlequin Ladybird produces a special, aggregation pheromone to attract other individuals to overwinterwing habitats. It has been proposed to use this pheromone within a network of traps in order to physically withdraw Harlequin Ladybirds from the environment. However, the cost of managing such traps is potentially too high to be feasible. The use of natural enemies of Harmonia axyridis, such as the ectoparasitic mite (Coccipolipus hippodamiae) that is capable to induce sterility in females of Harlequin Ladybirds, has also been considered, but alas with no practical applications so far. Therefore, this species is likely to be staying in the British Isles, apparently becoming another ‘native’ ladybird species with which we are to live (as it already happened with many other insect, crustacean and mollusc species).

The occurrence of Harlequin Ladybirds in Britain from 2004 to 2014 (one dot is equal to 10-km square), after Roy & Brown (2015).

In the following interview, Don Stenhouse, the Curator of Natural Sciences at the Bolton Museum, will share with us his own experience in studying the Harlequin Ladybird.

A full story of the Harlequin Ladybird in the UK can be found in the following paper:

Roy H.E. and P.M.J. Brown (2015), ‘Ten years of invasion: Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Britain’ – Ecological Entomology, 40(4): 336–348; online at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4584496/

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Taking Wing: curating a collection of Venezuelan hawkmoths

The following report has been prepared by Claire Miles, Honorary Curatorial Associate at The Manchester Museum.

Manchester Museum purchased the Adams and Bernard collection of 300 Venezuelan Lepidoptera in April 1976. Since then, if a curious curator removed the lids from the cardboard boxes to peer at the ghostly silhouettes in their translucent paper packets, the lids were always replaced. Now, thanks to funding from the Natural Science Collections Association (NatSCA), part of this collection – around 175 hawkmoths – can be set out, identified, catalogued, and made useful. This blog is a brief summary of progress so far.

Tantalising shapes – the moths in their paper packets.

In the paper packets, the hawkmoths lie with their wings folded together. With wingspans of up to 17 cm, setting the hawkmoths out will take up quite a bit of expensive storage space. Thanks to the NatSCA funding, the necessary glass-topped drawers can be purchased for the Entomology department’s new metal cabinets.

Entomology cabinets at Manchester Museum.

The entomology collections at Manchester Museum contain more than three million specimens including about two and a half million insects (Logunov & Merriman 2012; Logunov 2010). They already hold around 2000 hawkmoths (Sphingidae) representing around 270 species: 700 in the British collection, 850 in the C. H. Schill Worldwide Lepidoptera collection and 370 in the P. Schill Palaearctic Lepidoptera collection.

A drawer of the Death’s-head Hawk-moth, Acherontia atropos, in the British collection.

To put this in perspective, there are about 1500 known hawkmoth species worldwide, and this collection is a drop in the ocean compared to the Natural History Museum’s holdings of 289,000 Sphingidae. Curating and identifying the Adams/Bernard collection serves multiple purposes. It will extend the range of Manchester Museum’s Sphingidae, it will increase the accessible Sphingidae by about 9%, it will hopefully add some species new to the collection (and who knows, possibly completely new species), it will improve access to the collections, and it will improve their storage and security. In addition, I get to hone my practical skills setting the moths, with expert guidance from Phil Rispin, Curatorial Assistant in the Entomology Department.

Some of the hawkmoths have extremely long tongues. They pollinate flowers which provide nectar at the bottom of correspondingly long flower tubes, such as orchids and petunias.

Hawkmoths are fast-flying moths with streamlined bodies, present on almost every continent except Antarctica. They are pollinators as adults, and can be agricultural pests as larvae, which makes them ecologically and economically important, and their relatively well-understood taxonomy and fast response to environmental changes makes them useful environmental indicators (Camargo et al., 2016). This collection gives a snapshot of the species that were present in Venezuela 40 years ago when Mike Adams and George Bernard collected them in May 1975. This was one of a number of expeditions they mounted to Columbia and Venezuela in the 1970s and 80s, searching the high montane cloud-forests of the northern Andes for Pronophiline butterflies (a subtribe of the subfamily Satyrinae), on which they published a number of papers. The hawkmoths were collected in a region 24km north of Altagracia, Miranda State, at altitude 700m; from Guapo Dam, Miranda, and from Rancho Grande, Aragua, at altitude 1090m. The Museum’s Annual Report of 1976 describes the pair only as ‘University Zoology students’ at the time, although it appears they were recent graduates when they started their explorations (Adams, 1984).

Out of their packets, the hawkmoths were found to be in pretty good condition and the colours are remarkably fresh. Six weeks into the project, we have developed a routine – Phil puts the moths to relax in a damp atmosphere at the beginning of the week, and I (generally working one day a week) set them out at the end of the week.

A moth removed from its packet (Adhemarius species).

Moths relaxing in dessicator.

Each moth is set out, pinned down and left to dry for a fortnight (Adhemarius species shown here).

Once set, the collection data label and accession number are added to the pin. 80 moths have been set so far, and at a quick count those represent at least 20 species. The next step will be to identify them. Ultimately, the aim is to collate the information on all the Manchester Sphingidae collections into a single resource, and these stunning moths will be available for research and provide a fantastic resource for the museum’s teaching, displays, public events and engagement activities.

Erinnyis species before adding labels to the moth’s pin.

Eumorpha species.

Work in progress – some of the Adams/Bernard collection.

Claire Miles, Honorary Curatorial Associate at The Manchester Museum, working with the Adams/Bernard Sphingidae collection

References:

Adams MJ. 1984. Andean Butterflies – Search and Research. Alpine Journal. 89: 90­-96.

de Camargo AJA, de Camargo NF, Correa DCV, de Camargo WRF, Vieira EM, Marini-Filho O, Amorim FW. 2016. Diversity patterns and chronobiology of hawkmoths (Lepidoptera, Sphingidae) in the Brazilian Amazon rainforest. Journal of Insect Conservation. 20 (4): 629–641.

Giusti A. 2014. A whopping private collection – yet something still is missing.

http://www.nhm.ac.uk/natureplus/community/research/life_sciences_news/lepidoptera/blog/2014/03/17/a-whopping-private-collection, accessed 27 Feb 2017.

Kitching, I.J. 2017. Sphingidae Taxonomic Inventory, http://sphingidae.myspecies.info/, accessed 27 Feb 2017.

Logunov DV. 2010. The Manchester Museum’s Entomology Collections. Antenna 34 (4): 163–167.

Logunov DV & Merriman N. (eds.). 2012. The Manchester Museum: Window to the World. Third Millenium Ltd., London.

 

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