Hi, I’m Zoe! I’m a third-year Geography BSc student at the University of Lincoln and am just finishing a placement with My Square Metre. At the end of 2024, I wrote a couple of blog posts about the importance of invertebrates and how I was using pitfall trapping to investigate their population on some of My Square Metre’s land. If you missed these, Part 1 and Part 2 are linked here.
Identifying the Invertebrates
When I wrote my last blog post, I sorted through the invertebrates collected at each sample location and stored them in a preservative solution ready for identification.
Over the last month, I have been working through these samples to investigate the terrestrial invertebrate community in two different locations: My Square Metre’s existing wildflower meadow, and a field which is going to be sown later this year to create a secondary meadow. I split the secondary field into three separate distinct sections for my investigation: an area with longer grass, an area with shorter grass, and an area with short grass where the ground level dipped.
Using a stereo microscope with a zoom capacity of 20-80x, I set to work examining each invertebrate closely. I settled on classifying each invertebrate to the taxonomic level of class, order or family where appropriate, for instance into ‘Coleoptera’ (beetles) and ‘Opiliones’ (harvestmen). I used a range of taxonomic keys and pictorial guides to help me with this. I noted and photographed each distinct species found but decided not to scientifically identify to species level due to the high level of difficulty involved in this – there are so many different insect species that even specialist entomologists can struggle to name them!
Findings
In total, across the ten pitfall traps, we sampled 726 invertebrates from 74 different species. These fit into 13 different taxonomic classifications: Coleoptera (beetles and beetle larvae), Collembola (springtails), Araneae (spiders), Opiliones (harvestmen), Hemiptera (true bugs), Diptera (true flies), Diplopoda (millipedes), Lithobiomorpha (stone centipedes), Hymenoptera (bees, ants, and wasps), Acari (mites), Onsicidae (woodlice), worms, and slugs. Across the entire study, the most frequently encountered invertebrate classification was springtails (297 individuals), followed by slugs (130) and beetles or beetle larvae (117).
Firstly, I calculated the abundance (total number of individuals), and species richness (total number of species) for the samples at each location. The abundance ranged from 27 individuals in the meadow to 121 in the long grass section of the field. Species richness was also highest in the long grass area at 28 species, and lowest in the meadow at 14 species. The short grass and dipped short grass sections of the field ranked between the two for both metrics.
Following this, I analysed the average community composition in the four different areas, which revealed some interesting trends. For example, we found no slugs in the meadow, but they made up around 40% of the invertebrates sampled in the ‘short grass dip’ section of the secondary field. Additionally, around 57% of the invertebrates in the meadow and the long grass section of the field were springtails, but they made up only 11% in the ‘short grass dip’ section of the field. Springtails are tiny invertebrates which live close to or in the soil. They perform important ecosystem services such as breaking down organic matter, as well as acting as a food source for larger insects like spiders and beetles.
Some further statistical analysis suggested that the taxa identified may be exhibiting habitat-specific preferences. For example, the dipped area of the field may have been damper or more shaded which would create a more suitable habitat for slugs. Seeing that some important invertebrates preferred the areas where vegetation was longer highlighted how crucial it is to let areas of grass grow tall, as opposed to keeping it all mown short.
So, what does this mean?
Whilst some of the meadow’s lower-scoring metrics may appear negative, it is important to remember that this wildflower meadow is currently at the beginning of its journey – it was only planted two years ago. Preparing land to sow seeds inherently causes some level of soil disturbance, which will have a temporary negative impact on terrestrial invertebrates living close to the soil. Additionally, when I set the pitfall traps in mid-October, the wildflowers had already died back and gone to seed – the results may have been very different if the study had been done in June or July during peak flowering times.
Wildflower meadows are a very valuable habitat with high plant diversity, which provides many important ecosystem services. As such, the invertebrate community should bounce back and become even healthier than it ever was in years to come. Many insects have a short lifespan and high reproduction rate, so this recovery should happen on a relatively short timeline.
By writing a detailed report of the methodology I used in this study, My Square Metre will be able to repeat the investigation in several years, to assess how the invertebrate populations have recovered and benefitted from their work, both in the existing meadow and in the secondary field once this has been planted in the Spring. In the meantime, this study has given My Square Metre a valuable peek into the lives of many small invertebrates on their land, which are so important yet could otherwise have easily gone unnoticed.
