Seasonal and Daily Shifts in Substrate Use by Settling Butterflies: Conserving Resources for Invertebrates has a Behavioral Dimension

Arthropod habitats comprise utilities, such as places to rest, roost, locate mates, avoid enemies and thermoregulate, as well as consumables such as food supplies. We investigate the value of incorporating behavioral observations on substrate use within the standard mapping programme of the UK Millennium Atlas for expanding knowledge on resource use in butterflies. We find large differences among species and butterfly families in substrate use, including non-vegetation surfaces and human artefacts, when settled. Substantial differences in substrate use when settled and in settling height also occur seasonally and diurnally; settling height is at a minimum during the mid part of the day, whereas throughout the season there is an increase from spring to summer followed by a levelling off in autumn. Significant seasonal and or diurnal patterns occur for eight of the 13 species for which N≥30. Distinctions in settling height are affected by thermal environment and are related to two aspects of thermoregulation behavior, basking and wing appression, the latter both having seasonal components. These findings demonstrate the wide variety of surfaces required by butterfly species as habitat components over time. They also establish the importance of determining the behavior of individuals in relation to substrate use, biotope and vegetation units during standard recording surveys in order to determine the status of individuals located in recording units such as grid squares.