( xvi ) 



this point of view the recent memoir of Dr. Hagen on the variations of 

 Papilio Machaon is of great interest, although the difficulty of the subject 

 has already been manifested by the opposition to Dr. Hagen's views of so 

 excellent a lepidopterist as Mr. Edwards. 



I should be unwilling in this view of the subject to deny the intimate 

 connection of this question with the Darwinian theory of development, 

 but I would earnestly discourage my young hearers from following this 

 attractive theory too far, as it appears to me that it can only end in vague 

 speculations impossible of proof, especially whilst there still remain so 

 many interesting and important points which are capable of solution by a 

 careful and long-continued course of investigation. 



In addition to the systematic labours of the monographer and student 

 of the modern classification and description of species, the life-history 

 researches of such writers as DeGeer and Reaumur ; the special morpho- 

 logical memoirs, such as those of Lyonnet on the Cossns, or Straus Durck- 

 heim on the Cockchaffer, or that of Mr. P. H. Goose on the clasping organs 

 of male butterflies just published in the ' Transactions ' of the Linnean 

 Society, we must now add another special branch of the science, that of 

 Economic Entomology, — that is, the investigation and publication of the 

 natural history of such species of insects as are either beneficial or 

 obnoxious to mankind. The labours of John Curtis, as exhibited in his 

 fine work ' Farm Insects,' must here be referred to, and those of Miss 

 Eleanor Ormerod, whose unwearied proceedings are manifested in her 

 ' Annual Reports ' and in her most useful 'Manual of Injurious Insects.' 

 In America this branch of the subject has been carried much further than 

 in England, the appointment of State Entomologists by several of the 

 leading States of the Great Republic having led to the publication of several 

 very valuable series of annual reports on obnoxious insects by Messrs. 

 Riley, Comstock, and others.. The attention of our own Government has 

 at length been directed to the importance of this branch of the subject, 

 and I believe 1 am at liberty to mention that an important step will be 

 shortly carried out for bringing the subject in an official and satisfactory 

 manner before the general public. 



As 1 have elsewhere ventured to remark, the investigation of the precise 

 nature of the variations in any given species in a state of nature and the 

 causes which have led to such variations are of far higher importance either 

 than the establishment of new and independent species, or the study of 

 analogous modifications produced like those of pigeons under a state of 

 domestication. 



There is still another field of investigation opened to the entomologist 

 by the recent improvements in microscopes, especially in the movable appa- 

 ratus, by which lenses of different powers are brought to act upon objects 

 by means of a simple revolving disc upon which they are fixed. A still 



