l88 INTRODUCTION 



of a butterfly, but of course incapable of being rolled up.' H. Hagen (Proc. Soc. 

 Nat. Hist., Boston, xx, 1880, pp. 429-30) states that twenty-six species of Nemognatha 

 with thread-like maxillae are known in America. 



These species, as well as perhaps the foreign genus Chauliognathus Hentz. 

 (Telephoridae), with extraordinarily elongated stalk-like maxillae, and possibly also 

 some of the Euchiridae and Hoplidae, are placed by Loew among the hemitropous 

 flower visitors. All our indigenous beetles are allotropous or dystropous. 



Loew describes as allotropous (' Blumenbesuch,' II, p. 140) : — 



(a) Constant flower visitors with distinct structural adaptations for procuring 

 sap, and heterobiotic larvae (Lepturidae, Oedemeridae, some Cantharidae and 

 Lycidae). 



(p) Constant flower visitors with indistinct or no structural adaptations for 

 procuring sap, and heterobiotic larvae (Melyridae, Mordellidae, some Cistelidae, 

 Cleridae, Buprestidae, and Elateridae). 



(c) Flower visitors evolved from dystropous forms, with distinct structural 

 adaptations for procuring sap, and with heterobiotic larvae (Cetoniariae, Trichiariae). 



((f) Constant flower visitors with homobiotic larvae (Phalacridae, some 

 Nitidulidae). 



{e) Occasional flower visitors, of primarily carnivorous habit (some Cleridae, 

 Coccinellidae, and Staphylinidae). 



(y") Occasional flower visitors, of primarily saprophagous or xylophagous habit 

 (some Dermestidae and Ptinidae). 



According to Loew (op. cit.) the following are dystropous: — 



(a) Curculionidae, with proboscis. 



(3) Lamellicomia, with toothed maxillary lobes (Melolonthidae). 



(c) Chrysomelidae, with pronounced homobiosis of larvae and adults. 



• 



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

 tropous beetles occur in by far the greatest abundance on flowers with exposed 

 nectar, which are best adapted to their short proboscis, but they also visit flowers 

 with half-concealed nectar. The more deeply placed nectar of the other classes of 

 flowers is beyond their reach. Their marked preference for pollen induces them not 

 only to visit pollen flowers diligently, but also to devour this sort of food in the 

 blossoms of other classes, especially in social flowers, where it is especially abundant. 

 Loew's results ('Blumenbesuch,' II, p. 144) agree with this. — Flowers with com- 

 pletely concealed nectar, bee flowers, and lepidopterid flowers, are visited only to 

 a small extent by such unskilled flower guests as beetles, and such visits are as 

 a rule merely destructive. Pollen flowers and anemophilous flowers are much more 

 frequently sought out, as they afford welcome food to many beetles. Insects of this 

 order mostly affect flowers with exposed nectar and those which are social, the 

 former on account of the accessibility of their nectar, and the latter because they are 

 rich in pollen. 



In the Alps (Miiller, ' Alpenblumen,' p. 513) the visits of beetles to flowers are 

 divided on the whole very impartially between the different groups, which is to be 

 explained by the fact that many of them not only lick nectar or eat pollen, but also 

 devour any delicate floral structures. But even among them there appears to be 



