PROGRESSIVE MELANISM IN LEPIDOPTERA. ] G5 



Progressive Melanism In Lepldoptera. 



The attention of working lepidopterists is called to the collective 

 inquiry into progressive melanism, which has been set on fooc by the 

 Evolution Committee of the Royal Society. This inquiry was begun 

 in 1901, and, in response to the circular then issued, a good deal of 

 information was sent by collectors in various parts of England, to- 

 gether with a few returns from continental entomologists, some of 

 exceptional value. 



To assist in the maintenance of systematic records a coloured plate 

 has now been prepared, showing the most characteristic varieties of 

 the melanistic s^Decies. A copy of this plate, with forms for recording, 

 has been sent to a large number of those who might be interested in 

 the subject of the inquiry. Anyone who has not received these circulars 

 and would wish to see them is requested to communicate with W. 

 Bateson, Grantchester, Cambridge. 



As an investigation of this kind is one in which the help of local 

 organisations for the promotion of the study of natural history may be 

 of the highest value, the circular and the coloured plate have been sent 

 as far as possible to the secretaries of all natural history societies and 

 field clubs which were believed to have entomological members. 



To students of evolution the subject is one of exceptional import- 

 ance. It is well known to collectors that, within the last 50 years, 

 melanism has rapidly progressed in the case of some thirty species, and 

 that the change is steadily going on. It is certain both that within 

 the last decade many new species have become affected, and that the 

 distribution of the melanic varieties formerly known has extended to 

 districts where no such varieties formerly occurred. The melanics, 

 therefore, provide an unparalleled opportunity of watching an evolu- 

 tionary change proceeding at a sensible rate under our very eyes. It 

 is obvious that a record of the steps by which such a significant change 

 is being accomplished will give evidence of great weight in any attempt 

 to ascertain the nature of evolutionary processes in general. 



Collectors are, therefore, urged to miss no opportunity of noting 

 the first appearance of melanism in their districts, and, as far as 

 possible, to ascertain the proportions of melanic to non-melanic indi- 

 viduals in cases where both are already present. Precise numerical 

 information is, of course, most desired, but general statements as to 

 the present condition of any given species in a district are also of great 

 interest in view of the certainty that some ten years hence, at least, 

 an alteration will have become perceptible. 



As to the state of things in the districts most affected, which may 

 be spoken of as the northern midlands, the information received is 

 fairly complete, but records, ichether neiiatire or posifin', in regard 

 to the counties south of this area are greatly desired, and particular 

 information is wanted regarding Derbyshire, Leicestershire, Lincoln- 

 shire, Nottinghamshire, Shropshire, Staffordshire, Warwickshii-e, and 

 Northamptonshire. 



In view of the belief, to some extent supported by the facts, that 

 the spread of urban conditions favours the spread of melanism, the 

 appearance and spread of these varieties in the metropolitan area is 

 worthy of special study, and a good deal of important information on 

 this point has already been received. It is not a little remarkable that 

 June 15th, 1904. 



