PAMMEL — POLLINATION OF PHLOMIS TUBEROSA. 263 



hairy as in Monarda, Pedicularis, and Castilleia, is very effective, 

 especially against rain and dew. The same is true of the over- 

 arching spathe in Aroids. 



Ants, which from this standpoint must be regarded as entirely 

 injurious to flowers, are prevented from getting at this nectar in 

 various ways.* 



I. Aquatic plants arc protected by their isolation in water. Land 

 plants have occasionally secured for themselves the same ad- 

 vantages in that certain leaves form cups around the stem, in 

 others there is a leaf-cup at each joint, while in some there is a 

 single basin formed of the rosette of leaves at the base. In these 

 rain and dew not only collect, but are retained for a considerable 



* Loew has made the following very convenient classification of insects and their rela- 

 tions to flowers : 



i! I. Eutropic C'Eutrope"), Polytropic ('' Polytrope "J, Oligotropic ("Oligotrope"). 



o I 2. Hemitropic (" Hemitrope"). 



« I 3. Allotropic (" Allotro, e"). 



;^. I 4. Dvstropic (" Dystrope"). 



X J 



Eutropic includes all Apida with the exception of Prosopis and Sphecodcs. In these we 

 have reciprocal adaptations ; they cqllect both honey and pollen. On the whole they 

 must be regarded as useful ; in a few cases they are somewhat destructive. 



Hemitropic includes Prosopis and Sphectdes ; they are highly developed and have con- 

 siderable freedom of movement, but these only collect nectar, like Sphegida. 



Alio ropic includes the social Vespidce, the Ichneumonidce and TenikreJinidte. The mem- 

 bers of this group feed not only on nectar and pollen, but are also carnivorous. 



Dystropic includes the Formicidce; they are entirely destructive. The mandibles are strong 

 and well developed : the development of small teeth upon the mandibles enables them 

 especially to bite and gnaw. 



w J Hemitropic (Conopidae. Bombylida>, Syrphida?). 



^ 1 Allotropic (Muscida;, Empida;, Tabanidae, Stratiomydae). 

 P I 



. f Dystropic (Curculionidae, Melolonthidae, Chr)Somelid3e). 



£ Allotropic (Lepturida>, Melyridae, Cttoniaridse, Phalacridae, some Cleridas, and 



§•-( Dermestidx). 



~ I Hemitropic (Nemognatha and perhaps also some Euchirida?, Hoplidae, and Tele- 

 ^ I phorida.'. 



Most of the Lepidoptera are Hemitropic. Loew uses the word "Heterotropic" to desig- 

 nate the unequal selections that insects display in going to flowers. 



Anthophora pilipes and Anihidium manicatum visit few species, and confine themselves 

 to bee and humble-bee flowers of Labinta, Scrophiilariacece, etc., and are called Oligo- 

 tropic, as opposed to the many-sided visits of the species of Bombus which are called 

 Polytropic. 



