158 Mr. Robert M'Lachlan un the 



antennas, there was seen a small rounded raised object, 

 of polished texture, differing from the ordinary integu- 

 ment. If this be an ocellus, and I am not prepared to 

 say it is not, then its position is at variance with anything 

 yet recorded for these organs. 



My principal object here, is to explain the results of 

 an investigation of the structure of the external sexual 

 apparatus in the males, and its bearings on the question 

 of the supposed specific differences in the genus. And 

 in making this investigation I entered a new field of 

 enquiry, for this was my first essay at an examination of 

 this apparatus in Lejjidoptera. Many years occupied in 

 analogous observations in TricJwptera and Neuroptera, 

 have rendered me tolerably conversant with the infinite 

 variety of forms to be found in the sexual parts of those 

 insects, and have, probably, enabled me to form a tolerably 

 correct idea of the amount of difference necessary to 

 establish specific separation ; but it is very possible that 

 the same differences are not always present in Lepidop- 

 tera, and I am aware that the few Lepidopterists who 

 have attended to this much neglected, though essential, 

 part of their studies, affirm that these characters are more 

 of generic than of specific value in that Order. On this 

 point I am not competent to form any opinion, but having 

 had the curiosity to carry my examination a little beyond 

 the genus more especially under consideration, I have 

 been amazed at the complex and beautiful structure 

 revealed by denuding the scales of the anal extremities 

 of various Lepidopterous insects. 



In Acentropus I have endeavoured to make an exami- 

 nation of specimens from various localities. The only 

 places in which I have personally found the genus are 

 Hampstead near London, and on the Canal near Burton- 

 on-Trent. Besides those, I have seen specimens from 

 Ringwood in the New Forest, and from Cheshunt (taken 

 by Mr. W. C. Boyd) . Also individuals from Continental 

 Europe sent by Dr. Staudinger to my friend Dr. Knaggs 

 (to whom I express my obbgation for the permission to 

 make any use of the insects that I thought fit) , consisting 

 of two males (without female) sent as ^. niveus, and a male 

 (with am ply- winged female) sent as A. Jatipennis. Of 

 the English specimens all were accompanied by amply- 

 winged females, excepting those from Ringwood, of 

 which I have seen only males. 



