Surveying Invertebrates: Sampling Sites and Methods

Submitted by Olivia Watts on Tue, 14/12/2021 - 12:28

 Surveying Invertebrates Blog Post Advert. Dragonfly close up image and text.

There is a diverse array of invertebrates across the UK, and there are many reasons why you may need to survey them.  Join FSC BioLinks and Pete Boardman to learn more about the 'why' and 'how' of invertebrate surveying...

Why Survey Invertebrates?

Surveying invertebrates is an essential practice that helps inform conservation decisions and land management practices that are best for wildlife.
Where possible, species are identified in the field or from photographs, although this is only an option for a small selection of taxa. Many invertebrates are so small, or have very microscopic features between species, that it makes microscope use essential for identification. Unfortunately, this does mean that specimens have to be taken, killed, and preserved. However, once they have been identified and recorded, they become vital data for scientists and conservationists to evidence wildlife and environmental trends. In addition to this, preserved specimens are used as a reference to aid the identification of future samples.
It is important to remember that ethical guidelines and laws must be followed with any surveying or collecting. You can find the Wildlife and Countryside Act of 1981 here, which details any species that are protected by law. You can also find 'A Code of Conduct for Collecting Insects and Other Invertebrates' by JCCBI, the Joint Committee for the Conservation of British Invertebrates here.

Sweep Net Sample Collection

Selecting a Site to Survey

The site you are surveying will depend on the reason for a survey, permissions and target species. Sampling for a range of invertebrates would require sampling in as many different habitats as possible over a considerable period of time and using different methods. Invertebrates have complex life cycles, and things such as time of year, time of day, temperature, weather, and sampling method will affect the species you collect – even the colour of traps can alter the species you find.

Invertebrate Sampling Methods

Much like site selection, the sampling method used will also be determined by the reason for the survey and any focus taxa. Some techniques you may encounter are listed and described below, alongside the taxa that can generally be collected from them.

  • Sweep Netting – This method involves waving a sweep net through vegetation. Invertebrates can then be removed from the net using collection pots or pooters. It's a great method for collecting sheild bugs, leaf hoppers, hoverflies, spiders and flies - to name a few.
  • Direct Searching – This is more than likely a technique every entomologist has used, especially when we spot something that sparks our curiosity. It is one of the easiest surveying methods, as when the desired habitat is identified, it can be investigated. This can include looking under shelters such as rocks and logs, or searching through vegetation- just remember to put logs and stones back where they were. A pooter can also be useful to aid capturing invertebrates as you find them. Using this method, you can find a huge variety of invertebrate species, from earthworms to harvestmen and millipedes to beetles.
  • Sieving – Comparable to direct searching, sieving can help extract invertebrates from small debris such as leaf litter and rotting wood. This is another method that can pick up a vast range of invertebrates. For example, it can be useful to find larvae of flies or beetles, plus adult organisms such as worms, pseudoscorpions and earwigs.
  • Pitfall Traps – These traps are set to capture surface-living invertebrates in areas with low vegetation or bare ground. Containers are dug into the ground, with the top becoming level with the ground's surface which invertebrates will fall into. However, we discourage pitfall trapping unless it's essential, as it is an indirect trapping method resulting in lots of by-catches. If you use this method, please ensure that any by-catch is identified and recorded either by yourself or pass specimens onto someone else. Pitfall Traps typically collect taxa such as spiders and harvestmen, millipedes, centipedes and woodlice. However, it is particularly useful for surveying ground beetles and their larvae.
  • Light Traps – The use of light will attract many night-flying insects. These traps can range in complexity, but essentially they emit white/blueish light, and the insects it attracts can then be temporarily or permanently trapped. This method is perfect for monitoring moths; although you can find surprises in the traps, read more about the other species you may encounter here.

Moth Trapping

Sampling Sites for Invertebrates - by Pete Boardman

This webinar continues to cover why invertebrate sampling is a valuable method of site assessment when looking to improve or manage sites for biodiversity. Pete discusses what sort of surveys are needed to find invertebrates, how to undertake or commission these surveys, and what kind of outputs are needed to analyse the survey results. It also looks at sampling invertebrates in local site-based and larger landscape-scale surveys.

 Q & A with Pete Boardman

Can you poot specimens out of water?
Pete hasn't tried it but expects it would be difficult. Care would need to be taken to not ingest the water due to potential illness.

Are there any publications that have used Pantheon to compare habitats or habitat types?
Lots of consultant survey reports will highlight this. There are some publications in the Dipterists Forum, and some others are listed on the Pantheon website.
Some examples of Reports include:

Where can we find the lists of high-fidelity species for each habitat type? Are they available online anywhere?
It is a matter of interrogating the Pantheon website, with some examples at the bottom of this page.

How granular can Pantheon be? e.g. Comparing different grassland assemblages vs areas within one grassland habitat?
It depends upon the habitat type; different types of grassland are less well represented in Patheon than other habitat types such as heathland (open structured heathland v scrubby heathland).

Are there any alternatives to Pantheon?
There is nothing directly comparable with Pantheon. Instead, it uses some of the previous habitat and species quality indicators within it [in Patheon – click “Glossary” and then “quality index” from the tags column on the right-hand side for a list].

Can Pantheon be used to assess or compare habitat quality?
Yes- but it is only ever as good as the information you put into it.

Does the use of a net, e.g. sweep net, without the collection of specimens, count as a damaging activity and therefore require permission from Natural England if on an SSSI?
The vast majority of entomological work that might be carried out on SSSI’s and other protected sites will be useful for informing NE and their work, and it should be approved. It may need more thought if the target species are rare or protected, but generally, it shouldn’t be classed as a damaging activity as long as NE know about it and landowner permission has been granted.

Is there a good book or reference guide that lists invertebrate sampling methods and the pros/cons to help decide what would be best?
George McGavin’s book, Essential Entomology, is highly recommended. Pete is putting together a list to share. (ISBN 9780198500025)

Other useful resources on this topic:

  • Studying Invertebrates: Naturalists’ Handbooks – 28. Wheater, Cook & Phillips. Pelargic Publishing. (ISBN 1784270822). In fact, all of the Naturalists’ Handbooks act as great little introductions to the various areas of entomology they cover
  • For Diptera – A Dipterist’s Handbook (2nd Edition) Chandler, 2010. Amateur Entomologist. Though it contains no information on sampling methods, The Royal Entomological Society Book of British Insects by Peter C Barnard is a great introduction to the UK’s insects and highly recommended. (ISBN 1444332562)

In terms of a guidance book, I’ve heard that there isn’t one specific book, but one is currently in development?
An old research report is being updated to inform new methodologies and published in the near future. John Webb has been heavily involved in this version. The original document is;
Surveying terrestrial and freshwater invertebrates for conservation evaluation – Natural England Research Report – NERR005 (2007). Available here.

What factors do I need to consider when commissioning someone to come and survey my site as a contractor?
Ask to see previous reports they’ve compiled and ensure they will survey at an appropriate time of year. If you want a really detailed site survey, be aware of the time element (and associated costs) of carrying that out.

Useful Resources

Surveying Methods Literature: