Survey of Invertebrates in the B-Line
Josh Brown
Josh Brown
One of the goals of the Betchworth B-Line or biodiversity corridor project is to identify the invertebrates inhabiting the wildflower habitats. A baseline survey began in May and will continue through to September. Each of three sites has been visited once a month. To date over 120 species have been recorded at the three sites (Figure 1). The list of species will be documented on the Re-Betchworth Biodiversity website https://rebetchworth.weebly.com/invertebrates.html#/
Figure 1 Sites sampled within the Betchworth B-Line
Survey visits were carried out following guidance produced by Natural England (Surveying terrestrial and freshwater invertebrates for conservation evaluation1), to record invertebrate diversity via a range of sampling methods. This has mainly included direct observations, sweep netting, and ground searching, but plans to carry out some moth trapping will add significantly to the species list and give an insight into the diversity of nocturnal pollinators within the B-Line. Visits will continue into September as this is key to ensuring that species emerging both early and late in the season are not overlooked.
The assemblage of invertebrates recorded to date comprise a diverse range of groups, all with important ecological roles within the food web. This has included members of the following insect orders; Lepidoptera (butterflies and moths), Hymenoptera (bees, wasps, sawflies and ants), Diptera (flies), Odonata (dragonflies and damselflies), Orthoptera (grasshoppers and crickets), Coleoptera (beetles), and Hemiptera (true bugs), as well as 13 species of Arachnid (spiders and mites).
Butterflies are now on the wing in good numbers, and with insect pollinators being the main focus of the B-Lines project, it is great that a total of 19 butterfly species have been recorded within one location along the B-Line alone. Other important pollinators in the form of over 40 species of bee, wasp and fly have also been recorded including a range of eusocial, solitary, predatory and parasitic insects. The provision of other ecosystem services has also been apparent with decomposers (beetles and flies) making up a significant proportion of species recorded.
Figure 1 Sites sampled within the Betchworth B-Line
Survey visits were carried out following guidance produced by Natural England (Surveying terrestrial and freshwater invertebrates for conservation evaluation1), to record invertebrate diversity via a range of sampling methods. This has mainly included direct observations, sweep netting, and ground searching, but plans to carry out some moth trapping will add significantly to the species list and give an insight into the diversity of nocturnal pollinators within the B-Line. Visits will continue into September as this is key to ensuring that species emerging both early and late in the season are not overlooked.
The assemblage of invertebrates recorded to date comprise a diverse range of groups, all with important ecological roles within the food web. This has included members of the following insect orders; Lepidoptera (butterflies and moths), Hymenoptera (bees, wasps, sawflies and ants), Diptera (flies), Odonata (dragonflies and damselflies), Orthoptera (grasshoppers and crickets), Coleoptera (beetles), and Hemiptera (true bugs), as well as 13 species of Arachnid (spiders and mites).
Butterflies are now on the wing in good numbers, and with insect pollinators being the main focus of the B-Lines project, it is great that a total of 19 butterfly species have been recorded within one location along the B-Line alone. Other important pollinators in the form of over 40 species of bee, wasp and fly have also been recorded including a range of eusocial, solitary, predatory and parasitic insects. The provision of other ecosystem services has also been apparent with decomposers (beetles and flies) making up a significant proportion of species recorded.
Figure 2 Some of the butterflies in the Betchworth B-Line (Left to Right): Holly Blue (Celastrina argiolus), Comma (Polygonia c-album), Common Blue (Polyommatus icarus), and Small Skipper (Thymelicus sylvestris).
Figure 3 Some of the bees in the Betchworth B-Line (Left to Right): Early Mining Bee (Andrena haemorrhoa), White-tailed Bumblebee (Bombus lucorum), Gooden's Nomad Bee (Nomada goodeniana) and Common Furrow-bee (Lasioglossum calceatum).
The majority of invertebrates recorded so far have been common and widespread in terms of their conservation status and distribution within the UK. However, the location and underlying geology of the Betchworth B-Line has meant that a few species known to occur only within calcareous grasslands within the south-east have also been recorded. An example of this is a scarce species of False Firefly Beetle that was recorded within the garden wildflower meadow at Chalklands. This fascinating beetle exhibits one of the most extreme cases of sexual dimorphism in insects. The male beetle is approximately 10mm long, being a complete contrast to the flightless, slightly larger larviform female (see adjacent photos). ‘Females are terrestrial, living mostly in the shells of snails which they have killed with a poisonous bite and consumed with the help of injected digested enzymes. Adults appear from late spring until July or early August; males generally occur on foliage, flowers or high up on grass stems but a little later in the season may be seen wandering on pathways or on open areas of soil following the scent-trails of females, a function to which the expanded antennae are thought to be adapted’. (More information on this species can be found at https://www.ukbeetles.co.uk/drilidae)
Figure 4 Male (Top) and Female (Bottom) False firefly beetle (Drilus flavescens).
The more established wildflower areas within the B-Line have certainly yielded a higher diversity of invertebrate life than those more recently sown. This is to be expected, especially considering the poor weather in early spring. This initial survey will provide a useful opportunity to monitor how the assemblage changes as the project progresses and more favourable habitat for invertebrates emerges. The management of these newly created wildflower spaces will be crucial in ensuring that nutrient levels within the soils are kept as low as possible, allowing more species-rich swards to establish and therefore providing opportunities for a greater diversity of invertebrates to colonise them.
Source
1 Surveying terrestrial and freshwater invertebrates for conservation evaluation (NERR005) Available at: https://publications.naturalengland.org.uk/publication/36002