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Notes on Porthesia chrysorrhcea, L. 



By Robert Adkin, F.E.S. Read November 14//1, 1907. 



Porthesia chrysorrha'a is probably regarded by the average col- 

 lector as a very common species, yet those who have followed it at 

 all closely for a series of years will have noticed that, whereas at one 

 time it may have occurred in the utmost profusion, at another it has 

 been practically, or very probably actually absent. Whether this 

 was always so is difficult to say, but Derham who supplied the text 

 to Albin's plates in ' A Natural History of English Insects,' pub- 

 lished in 1735, savs w ith regard to the " Brown-tail" (of which both 

 larva and imago are figured, thus leaving no doubt as to the identity 

 of the species he is writing about), " The eggs of this caterpillar are 

 hatched in autumn, and the young feed upon the fleshy part of the 

 leaf, leaving the upper skin untouched ; they lay themselves up in 

 webs all winter, and as soon as the buds open they come forth and 

 devour them in such a manner that whole trees, and sometimes 

 hedges, for a great way together are absolutely bare. It will be well 

 worth while for those who value their trees or hedges to have the 

 webs cut off and destroyed during the winter." There can therefore 

 be no doubt that, at that time, the species was very abundant. In 

 1829 Stephens's "Illustrations of British Insects" was published, 

 and we there read of this species that " of late years it has been 

 rather scarce near London." And in Humphreys and Westwood's 

 "British Moths and their Transformations," published in 1844, it is 

 said of this species that it " has at times become so remarkably 

 abundant as to cause a serious panic to the Londoners, especially in 

 1782, when prayers were offered up in churches against the enemy ; 

 and the churchwardens and overseers of the neighbouring villages, 

 after offering rewards for collecting these caterpillars, attended to see 

 them burnt by bushels." 



It is very evident from the foregoing that the species was exceed- 

 ingly abundant in or about the years 1735 and 1782, but that in 

 1829 it was not so. Whether it had fluctuated to any very great 

 extent between those dates is not so apparent, but Westwood's 

 remarks rather incline one to think that it had. 



With regard to more recent times, I am able from the records of 

 my own observations, and such other data as I have been able to 

 obtain from friends, and the published notes of others who have 

 taken an interest in the species, to get together a fairly concise 

 account extending over a period of some thirty years. Commander 

 Walker tells me that when he was living at Sheerness in the early 

 seventies it was very common ; he then went abroad, and on his 



