After a sleepy start to summer, the sun has begun to show its face and a wonderful array of insects have emerged. Bees buzz in and out of flowers collecting yellow dustings of pollen, ants march in formation following the trails of pheromones left by members of their colony and flies dart about in the sky. Aside from the more charismatic species these critters often go unnoticed or are batted away by an irritable hand, yet they are, in essence, what makes the world go round.
Insects evolved around 480million years ago and have become the most diverse and dominant group of living things on the planet. Out of the 2.16 million known animal species a whopping three quarters are insects and experts suppose that there are millions more to discover (1). Without them ecosystems would collapse as they are integral to almost every food chain, and they play vital roles in many important processes.
Insects are key pollinators; 75%of crop species, 35% of global crop production, and up to 88% of flowering plant species depend on insect pollination to some extent (2). They are also incredibly efficient at decomposing animal and plant material which is important for soil health (3). Decaying matter improves soil structure, aids water retention and nutrient cycling which ensures the growth of healthy plants. Insects help us with pest control too! Ladybirds munch through thousands of aphids in their lifetime and parasitic wasps sneakily lay their eggs on caterpillars which eventually results in their death. The benefits that insects provide are endless and these are just a few of the many examples.
Over the last century, insect populations have declined drastically (4) with the primary reasons thought to be climate change, chronic exposure to pesticides and habitat loss (3). Wild Oxfordshire are working alongside Earth Trust, Church Farm Partnership and Lower Farm on the Yellow Wagtail Partnership (YWP; Yellow Wagtail Partnership) which, in part, aims to address these insect declines. Together, we are working to restore four miles of wetland meadows and pastures along the river Thames to reverse the declines of invertebrates, birds, and riparian grassland.
To get an idea of the insect populations and assemblages currently using the land in the YW Parea, a small group have been conducting research. Over the last five years Robin Buxton, and Sophie Cunnington, the YWP project officer, have been catching insect samples using a variety of traps from different sites along the river Thames. Equipped with dissecting microscopes and insect keys Mary-Emma Hermand and myself have been sorting the samples and identify them to family, and where possible, species level.
Despite the enormous amount of diversity amongst insects, they can be distinguished by three simple characteristics: six legs, three distinct body parts (head, thorax, and abdomen), and a pair of antennae. The broadest classification are groups called Orders of which there are 29 for insects. The largest and most diverse are Coleoptera (beetles), Lepidoptera (butterflies and moths),Hymenoptera (ants, bees, and wasps) and Diptera (true flies).
As many bird species, including the Yellow Wagtail and House Martins, forage on flying insects we have been focussing our efforts on Diptera (true flies) caught in emergence traps. Although no data analysis has yet been done, we have seen changes in insect assemblages between different months and the dipteran families that dominate, such as Phoridae, Cecidomyiidae and Sciaridae.
Often referred to as ‘dung flies’ as some species lay their eggs on animal dung, although this is for the minority. The most common species in Britain is Scathophaga stercoraria, the common yellow dung fly. If you take a closer look at a cow pat, you might see groups of furry golden yellow flies 3mm to 12mm in length sitting on the dung. These are male S. stercoraria waiting patiently to copulate with the greeny-grey and bristly females which land on the dung to lay their eggs(5).
One of the largest dipteran families and known as scuttle flies as they run in short bursts. They have diverse lifestyles and habitat preferences but are often associated with decaying matter. I have found this species easy to spot due to its humpback and reduced wing venation. These flies are very small ranging from 0.4 mm to 7 mm.
Peering down the lens of a microscope you feel as though you are entering an alien world. Suddenly hairs and bristles are revealed, big googly eyes are staring back at you and beautiful wing patterns emerge. The keys used to identify different families and species are based on these morphological features. Antennae are the starting point – antennae usually long and thin, no less than six free segments and uniform, or are there less than six segments? Moving down the key, differences in wing venation become a primary route to identify the correct family or species. At times, it can be very challenging and time-consuming judging the morphological features due to the diversity amongst the same families and species and sometimes the specimens are damaged from being caught and stored.
A group of predatory and blood sucking insects, the snipe flies are medium to large in size and are nicknamed ‘down looker’ flies after some species perching with their head downward on tree trunks (7).
Spending time inspecting and identifying insects has increased my appreciation for them, especially for the tiniest ones which usually look like black pin prick dots to the naked eye. After a fleeting bout of annoyance at all the bugs hitting my face as I cycle from a to b, I remind myself that we might not be here if it wasn’t for insects and how great it is that there are so many flying around this year!
If you want to do more for insects check out the guidance below:
· Helping Nature on Your Patch
· How to build an insect hotel - People's Trust for Endangered Species (ptes.org)
· How to grow a wildlife- friendly vegetable garden | The Wildlife Trusts
· How many animals are there in the world? Updated insect statistics
References
1. Intricacies of insect evolution revealed | Natural History Museum (nhm.ac.uk)
2. Widespread losses of pollinating insects in Britain. 2019 Mar 26; 10(1018)
3. The insect apocalypse, and why it matters. 2019 Oct7;29(19).
4. More than 75 percent decline over 27 years in total flying insect biomass in protected areas. 2017 Oct 18;12(10).
Read our August blog and marvel at the insect world with Jess...
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