LEPIDOPTERA 



173 



androconia in these cases, as in many other butterflies, are situated on the front 

 margin of the hind-wings, where there are spots resembling fungi ('brands'), which 

 consist of brush-shaped erectile structures. To avoid unnecessary evaporation, these 

 organs are covered by the hinder margins of the front wings, and for the same 

 reason the androconia are usually found on the upper surface of the wings of butter- 

 flies, which rest with their wings folded together vertically. Some Lepidoptera 

 possess odoriferous organs on the trunk, e. g. in some male hawk-moths they occur 

 on the under-side of the base of the abdomen. In Sphinx ligustri, S. pinastri, 

 and Acherontia atropos the androconia are well developed, in Deilephila euphorbiae 

 they are considerably less so. Similar organs also occur on the abdomen of some 

 owlet-moths. More rarely they are situated on the thorax (in the hawk-moth genus 

 Chaerocampa), and somewhat more frequently on the legs (many Noctuidae and 

 Geometridae, some Hesperiidae, and others). 



According to my statistical investigations ('Bliitenbesucher,' II, p. 11), hawk- 

 moths confine their visits almost entirely to lepidopterid flowers, the long corolla- 

 tubes or spurs of which correspond to their long proboscis. Occasional visits are 

 also paid to flowers of Class H, from which the insects know how to skilfully steal 

 the nectar. 



Social flowers which can be seen a long way off exercise the greatest attraction 

 on the remaining Lepidoptera, also the lepidopterid flowers which suit their long 

 proboscis, flowers with concealed nectar as deeply situated, and bee flowers. In the 

 Alps, which are particularly rich in Lepidoptera, these insects are compelled to visit 

 even such flowers as possess less conveniently situated nectar. In their necessity 

 they there make trial of even pollen flowers, which off'er them nothing, or from 

 which by boring they are perhaps able to obtain a trace of sap. 



Members of the most diverse groups of the excessively abundant alpine 

 Lepidoptera (H. Miiller, 'Alpenblumen,' p. 524) visit flowers in all stages of adaptation, 

 but they prefer secreted nectar to that which is enclosed in the tissues, concealed 

 nectar to that which is exposed, and social flowers to those which have to be 

 plundered one by one. They display such a preference for the social flowers of 

 Composites and related forms, that these receive from a third to about a half of all 

 their visits, which is almost without exception a far greater number than the lepi- 

 dopterid flowers and bee flowers together receive. 



With increasing length of proboscis (op. cit., p. 525) the Lepidoptera turn more 

 and more away from the shallower to the deeper supplies of nectar. For the silver-Y 

 moth (with a proboscis 15-16 mm. long) social flowers (S) cease to be the favourites, 

 the majority of its visits being made to the more abundant stores of bee flowers 

 and lepidopterid flowers. In the Alps as much as 94 % of the visits of Macroglossa 

 stellatarum (with a proboscis 25-28 mm. long) are paid to such forms, exactly half 

 these visits being to bee and humble-bee flowers, and half to lepidopterid flowers. 



With regard to colour preference, it has been shown both by the observations 

 of Hermann Miiller and by the investigations of E. Loew ('Blumenbesuch,' II, p. 129) 

 that Lepidoptera markedly prefer dark colours to bright ones. Reference has 

 already been made (pp. 124, 144) to the preference of certain Lepidoptera for 

 flowers resembling their own wings in colour. 



