194 INTRODUCTION 



The following belong to the group : — 



1. Hymenoptera. Long-tongued digging-wasps (Fossores, e.g. Bembex, Ammo- 

 phila) and ruby-wasps (Chalcididae, e. g. Parnopes), the solitary true wasps 

 (Eumenidae, e.g. Eumenes, Odynerus, and others), short-tongued bees (Apidae, 

 e. g. Andrena, Colletes, Dasypoda, Halictus, Panurgus, Prosopis, and Sphecodes, 

 to which also may be added Camptopoeum, Dufourea, Halictoides, Melitta, Macropis, 

 Nomia, and Panurginus). 



2. Diptera. Conopidae, Syrphidae, and Bombyliidae. 



3. Lepidoptera. All except the hawk-moths (Sphingidae), which belong to the 

 next group. 



4. Coleoptera. Only a few exotic beetles such as Nemognatha. 



III. Eutropous Insects. Completely adapted flower visitors of the greatest 

 value for pollination. They possess habits and structural modifications which further 

 in high degree their own ends in plundering flowers, while at the same time they 

 unconsciously effect cross-pollination in the most effective manner. They conduct 

 their visits to flowers with the greatest constancy and regularity of movements. 

 Corresponding to them in the plant world is an extraordinary variety of flower 

 adaptations that can only be explained with reference to the regularly occurring 

 cross-pollination effected by their visits. 



To this group belong : — 



1. Hymenoptera. Long-tongued bees (Apidae — Anthidium, Anthophora=Poda- 

 lirius, Apis, Bombus, Ceratina, Chalicodoma=Megachile, Chelostoma = Eriades in 

 part, Coelioxys, Crocisa, Diphysis=Trachusa, Eucera, Megachile, Melecta, Meli- 

 turga, Nomada, Osmia, Psithyrus, Saropoda = Podalirius in part, Systropha, 

 Tetralonia= Eucera (Macrocera), Trypetes=Eriades in part, Xylocopa, and also 

 Rophites). 



2. Lepidoptera. Hawk-moths (Sphingidae). 



IV. Dystropous Insects. Flower visitors not adapted to pollination. They 

 are either — as some beetles (Chrysomehdae, many Lamellicornia, CurcuHonidae, and 

 others), and also earwigs (Forficula) — wholesale flower devastators which devour 

 floral structures, or else their habits are detrimental to pollination, as in the case of 

 creeping flower guests (ants, aphides, thrips). It consequently follows that flowers 

 possess protective arrangements repelling their visits but no adaptations facilitating 

 them. There have in particular been developed in flowers a series of structures 

 serving to prevent the entry of these unbidden guests, which are mostly nectar- 

 thieves. 



Ants, which are described as dystropous by Loew, are not regarded as such 

 by VerhoeflF ('Bl. u. Ins. auf Norderney,' p. 169), but Loew (' Blutenbiol. Floristik,' 

 p. 387, note) calls attention to the fact that Hermann MuUer in his 'Alpenblumen' 

 also described ants as either valueless or harmful ( + ) for flowers, and of forty-three 

 ant-visits he observed thirty-four were dystropous. 



Loew describes as Pseudodystropy the case in which, ' even in completely 

 eutropous forms, adaptations may be secondarily acquired which render their owner 

 a devastator of flowers under special circumstances.' A very well-known example is 

 afforded by Bombus mastrucatus, which in the Alps gets at the nectar of many 



