TO MAKE A MEADOW IT TAKES A CLOVER AND A BEE - THE ENTOMOPHILOUS FLORA OF NW EUROPE AND ITS INSECTS

An analysis of the anthophilous fauna of N.W. Europe is presented, str essing the role plants play for insects. The study is based on some 29 ,000 relations between about 2,600 insect species and 1,300 plant spec ies (569 general. The data are derived from our database (''CrypTra'') of biotic relations between Cryptobiota and Tracheophyta, that is bas ed on published sources. It is suggested that a ratio of 2 to 5 anthop hilous insect species per entomophilous plant species is the rule in N .W. Europe, where other types of zoophily are virtually absent. A smal l minority of the plant species/genera play a disproportionally import ant role as hosts to flower visitors; many of these so-called cornucop ian taxa belong to the commonest entomophilous plants in the region, a nd occur also in moderately disturbed habitats. There is a significant positive correlation between the commonness of a plant species and th e fraction this plant represents of the trophic resources exploited by an insect species. There is, on the other hand, a significant negativ e correlation between the number of insect species visiting a given pl ant species, and the number of plant species visited by a given insect species. These two elements together demonstrate that the anthophilou s fauna and the entomophilous nora of N.W. Europe as a whole form a lo ose system, not predominantly characterised by specialisation. In acco rdance with this, factor analysis suggests that there is no ground to recognise more than three visitor types, viz., the allotropous, hemitr opous, and eutropous visitors as defined by Loew. A minority of the pl ant taxa - essentially the cornucopian ones - can with some difficulty be associated with these three types of visitors, and a very few narr owly specialised plant taxa can be associated with more specific visit or groups. However, the large majority of plants cannot be fitted in a ny typology. These results have practical implications for the nature management of the anthophilous fauna, in that the important role of th e cornucopian floral element is underlined. The fact that the majority of the cornucopian species are perennial, or even woody, places const raints to agricultural practices intended to foster beneficial anthoph ilous insects.