Butterflies, moths and bees as bedfellows

© Butterfly Conservation

© Butterfly Conservation

Katie Cruickshanks

Butterfly Conservation joined the Bee Coalition in 2016 as we were impressed by the messages coming out of the coalition and knew that we had to be a part of it. Our mission is to save butterflies moths and our environment and whilst the Bee Coalition is a natural place for us to be we felt that it was worth talking about butterflies and moths as pollinators, indicators and as part of functioning ecosystems. Our success as a species’ conservation NGO, has rested on a long history and obsession with Lepidoptera among British naturalists, dating back over 300 years and popularised by the Victorian collectors.  Butterflies are incredibly beautiful insects and have been revered and collected culturally for centuries.  They signify beauty and change through metamorphosis and these traits have been a big driver in the amount of research and data that we have at our fingertips today. 

Here at Butterfly Conservation we have worked for nearly 50 years primarily on the conservation of rare and declining species of butterflies and moths in the UK. In the last decade, the plight of more common and widespread species has shifted up our agenda.  In our recent State of Butterflies in the UK report (Fox et al., 2015) we communicated some devastating statistics about our ‘wider countryside’ species. Since 1976 our common species have declined by 25% in the UK and 30% in England.  Five of the 10 butterflies that have suffered the most severe long-term declines are wider countryside species.  These are iconic species which we associate with a healthy countryside such as the Small Tortoiseshell and Wall Brown which have declined by 73% and 77% respectively since 1976.

Our ability to produce accurate annual trends on all UK species is wholly dependent on an army of dedicated UK Butterfly Monitoring Scheme volunteers who walk regular transects at over 2000 sites each year.  This phenomenal data set has been growing since 1976 and it continues to be the most comprehensive and long running invertebrate monitoring scheme in the world.  Coupled with 11 million casual butterfly records and nearly 23 million moth records used to map distribution and model site occupancy over time, we have a uniquely powerful dataset on a subset of invertebrate pollinators.

So what does this mean for the Bee Coalition? Bees are the headline grabbers in these harrowing times of fears over ecosystem services, pesticides and food production.  Bees are undoubtedly the most commercially significant group of insects (followed by hoverflies) when it comes to getting food on to our plates.  But it’s the diversity of pollinators that is important for pollination for all our wild flowering plants.  This underpins all our flower rich habitats and their biodiversity further up the food chain.  Whilst butterflies and moths might not be out there doing the pollination leg work for commercial crops such as soft fruits, beans and apples etc., there are over 2500 species of Lepidoptera most of which are visiting flowers in the adult stage of their life cycle. Such a high level of diversity for one group of flower visiting insects is a compelling case for their importance especially when compared to 270 species of bees and 280 species of hoverflies. 

Butterflies and moths are equally at risk from the impacts of pesticides.  The major focus of the Bee Coalition’s work has been action on neonicotinoids and Butterfly Conservation is in full support of this campaign. We undertook some research with the Universities of Sussex and Stirling and the Centre for Ecology and Hydrology which showed that the number of hectares of farmland where neonicotinoid pesticides are used is negatively associated with butterfly indices (Gilburn et al., 2015). The study found population trends of 15 species showed declines associated with neonicotinoid use, including Small Tortoiseshell, Small Skipper and Wall species. Whilst a causal link between butterfly and moth mortality and neonics use is yet to be confirmed in the UK, there is strong evidence from Monarch caterpillars and their success in the USA (Pecenka and Lundgren, 2015).

The diversity of life stage requirements within the 2500 species of moths and 59 species of butterflies in the UK adds strength to their importance as flower visiting insects and pollinators.  Whilst all pollinators undergo the four stage life cycle (egg, larva, pupa, adult), the sheer number of Lepidoptera species means that conserving habitats for them will go a long way to helping other pollinator groups.  Firstly the larval stage for butterflies and moths is dependent on specific foodplants.  For common and widespread species this may be as generic as polyphagus moths feeding on deciduous trees such as oak, birch and willow species, through to highly specialised species whose larvae feed on only one, often rare, plant species. The range of larval foodplant requirements across Lepidoptera translates into a need for a diverse wider countryside coupled with expansion and conservation of rare habitats and plant species for breeding. 

Most species of butterfly and moth overwinter in a non adult stage (mostly in the larval stage). Moths, in particular, are known to inhabit all habitats from the shoreline to the mountain top and occupy a wide variety of ecological niches.  There are British Moths whose caterpillars feed on roots wood, aquatic plants, lichens, algae, honeycomb, fungi, dung, fur and feathers. However, at least a third of moths over winter inside vegetation as larvae or pupae and around two thirds of butterflies do the same. Once they have completed the larval development stages by feeding on the plant material of choice, many of them seek longer tussocky vegetation, dead seed heads and hollow stems for the winter.  It is these pockets of uncut, untidy vegetation that are supporting the next years populations of butterflies and moths, not to mention a whole suite of other pollinators (bees and hoverflies included) that require tussocky vegetation for nesting and overwintering in the wider countryside.

Beyond pollination services, butterflies and moths are important food sources for taxa further up the food chain.  Birds and bats in particular are documented to consume huge numbers of Lepidoptera especially the larval and adult stages.  There is an estimate of 35 billion caterpillars consumed by Blue Tit chicks annually in Britain alone. All 16 species of bat in the UK feed on adult moths to some extent and for at least 10 species, moths make up a substantial part of their diet. 

Maintaining strong populations of Lepidoptera in a well-connected and diverse countryside will generate multiple benefits for insectivorous species and will support habitats for a wide variety of other pollinators and insects including those commercially important bees. The management tools to delivering these outcomes are well known: conserving priority habitats and species, looking after and buffering the pockets of semi-natural habitats, decreasing the intensiveness of farmland, encouraging better connectivity of habitats (hedgerows and margins), rotational management- leaving areas uncut over winter and creating more flower rich areas to provide vital pollen and nectar resources. With this knowledge, the wealth of scientific evidence and data, coupled with strong partnerships between NGOs, the public and others we can help create a countryside that’s rich and abundant in flower visiting insects. Harnessing public support and ensuring that this message gets through to governments and decision makers is what the Bee Coalition is about. Adding our voice to the Bee Coalition was an easy decision for us at Butterfly Conservation.

References:

Fox, R., Brereton, T., Asher, J., August, T., Botham, M., Bourn, N., Cruickshanks, K., Bulman, C., Ellis, S., Harrower, C., 2015. The State of the UK’s Butterflies 2015.

Gilburn, A.S., Bunnefeld, N., Wilson, J.M., Botham, M.S., Brereton, T.M., Fox, R., Goulson, D., 2015. Are neonicotinoid insecticides driving declines of widespread butterflies? PeerJ 3, e1402.

Pecenka, J.R., Lundgren, J.G., 2015. Non-target effects of clothianidin on monarch butterflies. Sci. Nat. 102. doi:10.1007/s00114-015-1270-y