( cxvi ) 



will explain the changes of conditions of life in time ; and the 

 laws of variation, diversified in details as are the species 

 themselves, will exjilain the rest."- 



Mr. Bethi;ne Baker in his Address had occasion to refer 

 to the genera Ichthyurus and Psalidura, but he could hardly 

 have suspected how interesting an illustration of the modifi- 

 cation of parts those genera afford. Ichthynrus is a genus in 

 which I had, myself, previously been very much interested 

 for another reason. It belongs to the family Telephoridae, 

 and several years ago I had discovered in nearly all the beetles 

 of this family a series of small apertures, distinct from the 

 si)iracular openings, along the sides of the first eight dorsal 

 ])lates of the abdomen, a pair to each segment. In some 

 genera they lie well within the lateral margins ; in others 

 they are placed close up to, or quite upon, the postero -lateral 

 angles, excepting the first pair, which always retain their 

 position inside the margin of the first tergite ; and in a few 

 genera they are situated at the apex of very distinct lateral 

 processes which point outwards and slightly backwards. In 

 appearance these apertures are not unlike some forms of 

 spiracles ; each has a circular chitinous rim bordering a small 

 pit lined with a pale membrane in which is a still smaller 

 opening fringed with fine hairs, and which evidently is the 

 external opening of a gland. Segmentally arranged glandular 

 apertures of this kind are known in the larvae of some Coleo- 

 ptera, Lepidoptera, and otlier insects, and the secretion is 

 considered to be distasteful and protective. J\Iiss Olga Payne, 

 with whom I was in corres^^ondence when she was working 

 on the structure and life-history of one of our species of Tele- 

 phorus, has found the glands also in the larva of that genus, 

 and in the three thoracic as well as in the first eight abdominal 

 segments, and has given a description of them in a paper since 

 published ; but she has expressed a doubt as to whether they 

 are really functional, since the openings were very small and 

 no liquid secretion seemed to come from them. So far, how- 

 ever, as the imago is concerned, there can be no doubt that 

 they are functional; for in handling some living specimens I 

 have myself seen drops of a clear liquid of pretty considerable 

 size issue from the pair of apertures on the eighth segment, 



