Unusual fly found in Museum garden nature bioblitz

26 May 2011

An unusual fly has been found in the Natural History Museum’s Wildlife Garden after a nature bioblitz to celebrate the International Day for Biological Diversity last Sunday 22 May.

The larvae of the scarce drab wood soldier fly, Solva marginata, feed on rotting wood under bark, which is quite unusual. Most species of fly have larvae that feed on other decaying or living plant tissue, fungi, micro-organisms or dung. Others are parasitic or predatory, and some are aquatic.

Although more well-known, the percentage of fly species that breed in dead or decaying flesh (carrion) is very small. We know about these species because of their association with people, either contaminating food, spreading disease or because of their use in murder investigations.


The fly was found while Museum scientists and visitors were counting as many species as they could in the Big Nature Count 24-hour census, or bioblitz. 

This was part of the Big Nature Day to highlight the importance and loss of biodiversity and help visitors get up close to the nature around them and understand more about it.

Stuart Hine of the Museum’s Identification and Advisory Service took part in the Big Nature Day and says, ‘The drab wood soldier fly seems to be associated with poplar trees more than anything else, so the tree in the wildlife garden is probably where this fly came from.’

Like a sawfly

The drab wood soldier fly was identified by its size and characteristics such as the pattern on its wing-veins and its short multi-segmented antennae. ’In its general appearance it looks quite like a sawfly,’ says Nigel Wyatt, fly expert (dipterist) at the Museum. 

‘It has a largely blackish body with bright yellow markings at the tip of the thorax and at the base of the abdomen, and narrow pale bands on the abdomen.’

It is the first time that the drab wood soldier fly has been recorded in the Museum’s wildlife garden.

Scarce species

The drab wood soldier fly is uncommon in the UK. Although quite widespread, found mostly in the southeast England, East Anglia and East Midlands, populations are only found in specific local areas, making it quite scarce overall.

It is a Nationally Notable B’ Species, which means it is one of 2 categories of nationally scarce species that are monitored to assess how their populations are changing.

70 years since the last fly found

Records of the drab wood soldier fly are low in the UK. The last time one was found at the Museum was nearly 70 years ago, as Wyatt explains. ‘Another specimen was collected at the Museum in 1942 by Ralph Coe, who was then a curator of Diptera in the Entomology department.’

This new fly specimen will be a valuable addition to the national natural history collections at the Museum. Wyatt explains, 'Especially with smaller insects such as flies, which usually cannot be identified accurately in the field, collecting and preserving specimens is essential so that they can later be examined under a microscope, which is usually the only way to get them positively identified'. 

The new specimen will also help to provide a permanent reference for this fly species, which other specimens can be compared against to check identification. 'The reference collection at this Museum plays an important role in conserving scarce insects such as this,' says Wyatt, 'because the collecting data on the specimens helps to record distribution, and to determine which areas need to be conserved for their survival. 

'If these insects are collected in a limited and responsible way this causes much less damage to their population than if their habitat were to be destroyed.'

Identifying species in the big nature count

Hundreds of other plant and animal species were found in the Big Nature Count but it will take more time for most of them to be identified. The specimens collected from the bioblitz will be studied and added to collections and will give a much better understanding of the biodiversity right on the Museum’s doorstep.

  • by Yvonne Da Silva
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