G. T. PORRITT : PRESIDENTIAL ADDRESS. I05 



birch-twig-like larvae of Ennonios autumnaria^ and indeed in the 

 larv£e of all the species of Ennomos and the allied genus 

 Selema, with many others. And how marvellously too do the 

 green larvge of Pseudoterpna cytisaria resemble the shoots of 

 broom ; and young Geometra papilioiiaria, the brown catkins of 

 birch ; those oi Fidonia pin i aria and Thera variata the 'needles' 

 of pines ; Cleora glabraria, C. lichenaria, and Boletohia 

 fuligiiiajia, the respective lichens to which they are attached ; 

 and so on. But the larvae of two of our most beautiful ' Green 

 Emerald Moths,' Phorodesnia hajidaria and P. sinaragdaria, 

 contrive their mimicry in an altogether different fashion. Their 

 natural colours are not conducive to their continuity as species, 

 and so their first performance immediately on quitting the ^gg, 

 even before feeding, is to secure protection by dressing them- 

 selves. P. hajidaria at once cuts out pieces of oak leaf, and 

 fastens them one by one all over its body, whilst P. smaragdaria 

 does precisely the same thing with the leaves of its food plant, 

 Artemisia maritima, until they are quite covered. When the 

 process is completed, they are of course exactly the colours of 

 their food in a fresh state, but even as their dresses gradually 

 become discoloured and finall}^ brown, through the withering of 

 the fragments of leaf, they just as strongly resemble the dead 

 and dying leaves, of which there are always plenty in the same 

 stages of decay, on the trees and plants. For many years the 

 larva of P. smaragdaria completely baffled the close search of 

 lepidopterists, until Mr. Elisha at length discovered it through 

 the moving of a bit of apparently dead Artemisia he had beaten 

 into his umbrella. Time will not permit of my continuing this 

 subject further, but enough has been said to shew the lines on 

 which this single branch of a wide subject is being now pursued. 

 And we know that our botanists and the other scientists have 

 made equally wide and advanced strides in their researches and 

 methods of work. 



A few words on Field Meetings may not be out of place. 

 Our Union is essentially a field meeting association, and 

 indeed almost all the work it does collectively is in this way. 

 During the past 25 years we have explored nearly every part of 

 our county, though it must be confessed in many cases not 

 very thoroughly. Sometimes the weather has been dead 

 against outside scientific investigation, as those of us, for 

 instance, who attended the Arkengarthdale excursion in 

 August last well remember. No doubt this uncontrollable 

 element is a considerable drawback, for it is not pleasant after 

 we have made all arrangements for an enjoyable and successful 

 expedition, and have perhaps already reached our ground, to 

 have all operations stopped by a deluge of rain, as was the 

 experience in the one to which I have alluded ; for even if it 

 clears up shortly afterwards, everything is often so completely 

 soaked, that it requires an exceptionally ardent naturalist to 

 thoroughly enjoy his or her collecting and investigation among 



