THE GYPSY MOTH IN ENGLAND. 271 



others, none of which show any indications of a decline in a 

 foreign country. The idea of Mr. Weir, that they were de- 

 stroyed in England by collectors, hardly seems worthy of 

 consideration. I will not attempt to express an opinion as to 

 the cause of their extinction in that country, but it seems 

 to me that it must be due to causes not yet understood ; and 

 if the profound thinkers in entomological matters, of whom 

 England has so many, have not satisfactorily settled this 

 question, it would be folly for me to express any decided 

 opinion on the subject. I wish, however, to call attention 

 to one or two points. Great Britain, because of its insular 

 position, the prevailing winds and the currents in the sur- 

 rounding ocean, has a far diflerent climate from that of 

 Massachusetts or the interior of Europe and other parts of 

 the old world, where this insect is usually most abundant. 

 I noticed, when in England, that the foliage of all vegetation 

 seemed darker than in this country, or, at least, than in the 

 eastern part of it ; and it occurred to me that this might be 

 due, in part, to the larger amount of moisture in the atmos- 

 phere, especially as quite similar conditions of climate, with 

 darker foliage occur in British Columbia, as I have been in- 

 formed by my colleague, Mr. E. H. Forbush, who also states 

 that the arboreal animals of that region are much darker than 

 those in the eastern parts of the United States. Some years 

 ago, while in England, my kind friend, Mr. C. G. Barrett, 

 gave me a very complete series of British Tortricids, and 

 I never look at my collection without noticing how much 

 darker these insects are than the same species from Germany 

 and other parts of Europe. It seems to me that this dark- 

 ening may have resulted from natural causes, operating 

 through a very long period of years. When these insects 

 first made their way into the British forests and fens, with 

 their darker surroundings, the lighter colored individuals, 

 contrasting the most with the objects on which they rested, 

 naturally fell a prey to their enemies more readily than the 

 dark-colored individuals ; the darker ones were left to propa- 

 gate the species, and, in time, a dark race was formed. I 

 am well aware that I am now trespassing on ground which 

 is far better understood by my English brethren, but T trust 

 that I may be permitted to call attention to this matter for 



