butterflies and moths
The life histories of butterflies and moths are complex, with caterpillars and adults having quite different food and habitat needs. Some species are quite mobile and as adults can easily move to find new habitat to meet their needs, other species are more sedentary/fixed and need to find all their requirements for nectar, larval food plants and over-wintering hibernation shelter within the same location.
Adult insects mainly feed on nectar and need habitats rich in flowers at the time of year they are in flight. Flower rich meadows and grassland offer a diversity of nectar sources which attract butterflies and moths. Nectar rich plants like birdsfoot trefoil, knapweeds, vetches and clover are important, particularly for those species associated with grassland such as meadow brown, gatekeepers, skippers and common blue. Plants whose flowering period coincides with the flight period of particular species are particularly well visited. Later flowering field, small and devilsbit scabious are all very attractive to later broods of tortoishells, peacocks and commas, as are wild marjoram on chalky soils and hemp agrimony and fleabane in wetlands.
Larval food plants
A key habitat requirement for all species will be the availability of suitable food plants for caterpillars. Grasses are larval food plants for a large number of butterfly and moth species. Some species like skippers and ringlets prefer tall coarser grass species, others like gatekeepers, meadow browns and marbled whites prefer fine grasses such as bents and fescues. Other food plants worth noting are birdsfoot trefoil for common blue, garlic mustard for orange tip and green-veined white, and common sorrel for small copper. All these species are easily provided as common components of meadow seed mixtures, or hedgerow/woodland mixtures in the case of garlic mustard. In practice the contribution sowing these food plants makes to population sizes of a given species will vary. We have observed an increase in common blue butterflies wherever we have grown birdsfoot trefoil on our Norfolk farm. Common blue butterflies are a relatively mobile species and its food plant, birdsfoot trefoil, was not common locally until we started growing it. In contrast there is probably rarely any benefit in planting or encouraging nettles as a food plant for small tortoishells, peacocks and comma butterflies as it occurs so widely and abundantly in all environments that it is never in short supply. And finally we sadly cannot make any claims that if you sow milk parsley you will attract a breeding colony of swallowtail butterflies!!
The vegetation structure and management (=disturbance) of a site is also important and requirements can vary from species to species. For meadow brown butterflies the ideal habitat is traditionally cropped hay meadow (hence their name) where eggs can be laid after the hay has been cut mid summer. The caterpillars emerge and feed on the young autumn re-growth until they hibernate as part grown caterpillars at the base of the sward. Gatekeepers need shrubs as well as grassland and can be found at the edges of grassland in woodland rides and hedgerows. Many species overwinter as caterpillars or pupae in the tussocky base of grass plants and will need some areas of rough undisturbed grassland to take refuge in. Continuously mown or grazed grassland is of limited use for many insects and even seasonal cutting of meadows can be quite disruptive for some species. In locations that are not over-managed there are usually rough corners and margins that if left undisturbed can provide a good refuge. In managed landscapes and gardens it is good to leave some grassland uncut through winter or perhaps sow a dedicated area with tall tussocky grasses (mix EM10).