Grateful thanks to all persons who contributed to the improvement of our knowledge on the biology and ecology of butterflies. This included dealing with experiences, providing rearing material, guiding to special localities and not at least, growing friendships. The period of research covered a period of twenty years, a period during which the interest in butterflies evolved from just admiring these creatures into promoting them as a subject for nature conservation. In the beginning of conservation practise the environmental requirements of plants and birds were the leading subjects in determining policy and reserve management. The butterflies with their typical requirements of hostplants and space were not integrated. Collaboration with colleagues in conservation research changed this and allowed butterflies to take a more central role as indicators of processes over time and quality of landscape. This resulted in the concept of the four functions, an idea of the late Chris van Leeuwen (Research Institute for Nature Conservation).
The visit to famous butterfly localities in adjacent countries has been made possible by the following persons:
England: Herold Short † (Esher, Hindhead), Eric Duffey † (Monks Wood Experimental Station).
Sweden: Ole Hammarstedt (Södra Sandby), Christer Wiklund (University of Stockholm), Niels Anderson (Nature Centre and Research Station on Öland).
Germany: Sepp Weidemann † (Untersiemau), Wilfried Hasselbach (Alzey), Ernst Urbahn † (Zehedenick).
France: Ferdinand Borde (Annecy).
Special appreciation for Jeroen Voogd for his help in computer queries and for the supply of many of the beautiful photographs.
The following people are thanked for the provision of rearing material:
Jan Burgers (M. athalia, L. megera).
Peter Cribb (E. aurinia).
Nico Elfferich (M. aurelia).
Wim Geraedts (T. action, A. agestis, T. betulae, A. paphia, S. sertorius).
G. Kleinecke (S. w-album).
Pim Kuyken (A. agestis).
Jan van der Made (L. tityrus).
Jan Meerman (D. plexippus).
Ingo Nikusch (P. apollo, T. betulae).
Jan van Oordt (B. aquilonaris, P. optilete).
Jorg Rüetschi (C. palaeno).
Harold Short (L. dispar, A. ilia, A. iris, L. populi, S. pruni, F. quercus).
Piet Sogeler (B. eunomia, L. helle).
Jos Stevens (A. daphne).
Jeroen Voogd (M. phoebe).
Sepp Weidemann (P. apollo, A. ilia, L. populi, S. spini, S. w-album).
Christer Wiklund (C. palaeno).
Rob Zwart (P. brassicae).