February — March iSSg. 



PSYCHE. 



173 



volved upon Uelpino ( 8 ) , whose 

 evidently thorough studies are now in 

 course of pubHcation, the results already 

 printed occupying over 150 quarto 

 pages. 



Broadlv speaking, this class of extra- 

 floral nectar-glands, by their secretion, 

 attracts to the plants which bear them 

 hordes of ants (rarely wasps), which 

 constitute a temporary and changing 

 body guard, disputing the presence of 

 all other insects with the exception of 

 their prot^g^s the sugar-excreting 

 aphides, coccids, etc., and resisting, 

 often furiously and effectively, the on- 

 slaughts of ruminants and other large ani- 

 mals. That this is a true explanation of 

 the reason for the existence of these 

 structvu'es, is generally admitted, today.* 



The plants which possess such glands 

 are phaenogams and ferns, chiefly of the 

 tropics and subtropics ; yet the number 

 in our own and other temperate floras 

 is rather surprisingh* large. 



The ants attracted by extra-nuptial 

 nectar are mainlv the omnipresent, om- 

 nivorous species. Protection is often 

 aflbrded against various caterpillars and 

 other leaf-eating larvae, as Ratzeburg 

 (24) and others have observed; but 

 the body-guard appears primarily des- 



* For a general negation of the prevalent notions 

 concerning nectaries of all sorts, coupled with a good 

 histological study of many of these organs, reference 

 should he made to Bonnier's essay- - Les Nectaires — in 

 Annales des sci. nat., Bot., 1S79, v. S. also published 

 separately at Paris, — which reverts to the theories of 

 the last century. 



It is also to be observed that Kerner von Marilaun, 

 the learned Viennese biologist, quite recently describes 

 -the petiolar glands of Populus as organs of absorption 

 Pflanzenleben, v.1.215), — but without giving reasons 

 for his belief nor an indication that anotlier function 

 had been previously ascribed to them. 



tined to resist the depredations of otlier 

 members of their own group, — the leaf- 

 cutting ants, — which swarm in tropical 

 and subtropical regions, and cpiickly 

 defoliate plants not provided with this 

 defence unless efficient senice is ren- 

 dered by colleters or alkaloids, which 

 prevent the access of these insects to im- 

 mature and tender parts, or render these 

 distasteful to them. Delpino was at first 

 inclined to explain the occurrence of 

 protective nectar in regions where no 

 leaf-cutting ants are fovmd, solely with 

 reference to herbivorous larvae. But 

 it has been showm several times that 

 such larvae are permitted in large num- 

 bers on plants provided with a body- 

 guard of ants attracted by nectar. I 

 have myself observed this in the case of 

 Gossyphim, which suflers notoriously 

 from the attacks of Aletia and Helio- 

 tJiis^ although it is unusually well sup- 

 plied with extra-nuptial nectar that at- 

 tracts numerous ants which to a certain 

 but insufficient extent do attack the cat- 

 erpillars of the moths named. The 

 same thing is also to be seen on Populus 

 monilifera in the west and south, where 

 this tree is subject to very disastrous at- 

 tacks from the larvae of a chrysomelid 

 beetle, Plao-iodera scripta^awiXa moth, 

 Acronycta poptiJi. Careful obsei-va- 

 tions of the behavior of insects attracted 

 b}' extra-nuptial glands, carried through 

 a number of seasons, and on plants with 

 differing surroundings, accompanied by 

 correct identification of the insects are 

 possible to local entomologists eveiy- 

 where, and are much to be desired. 

 There seems little reason to doubt 



