^ ( cxx ) 



metamorphose est aussi problematique que celui des cocardes 

 des Malachius." 



These interesting explanations of the movable spines of 

 Acrocinus longitnanus should serve to remind us how far from 

 infallible are even the most trustworthy of authorities, and 

 how careful we should be in our statements to make sure 

 beforehand of our facts. Many of you are. doubtless, familiar 

 with the Harlequin-beetle, and know what the truth in regard 

 to its prothoracic spines really is : that they are not in the 

 least movable but are absolutely fixed and as firmly consoli- 

 dated with the sides of the thorax as the corresponding spines 

 in many other Longicorn beetles. The idea that they were 

 movable arose from superficial observation and was due to 

 the fact that they are surrounded each at the base, but on 

 the upper side only, with a rather deep narrow groove ; it 

 began with Linnaeus himself when he described the beetle, 

 and was never questioned until, just about a century later, 

 the mistake was discovered and set right by James Thomson. 

 Mr. Crampton evidently had no knowledge of that fact, 

 and he is hardly to blame for having accepted as true a state- 

 ment made on such excellent authority. 



But though one of the instances on which he relied is gone, 

 there is no reason why he should not find in the forcipate tail 

 of Ichthyurus another that would answer the purpose of his 

 argument almost as well. For if I am right in the interpreta- 

 tion I have given to it, you have there a pair of movable 

 appendages developed from what were once fixed lateral 

 processes, comparable with the prothoracic processes of the 

 Harle quin -bee tie . 



In the long forcipate tail appendages of Psalidura, a genus 

 of Curculionidae, we have another example of perfectly mov- 

 able structures which have apparenlly developed from fixed 

 rigid processes. I say apparently, because, while they are 

 free from the eighth tergite, to which they are attached by 

 membrane on the dorsal side, in one species of a related genus, 

 they seem to be more or less iiniily united to the sternal 

 j)late on the ventral side. But whether developed as processes 

 from the tergum or from the sternum, it is fairly certain that 

 they have not originated in any other way, and 1 have little 



