Mb '2 WjD OF PRESER VING INSECTS. 529 



completely failed. Wherefore, in conclusion, I venture to recommend 

 the preserver of insects not to put much trust in simples. 



"Contra vim mortis, non est medicamen in hortis." 

 Against the deadly moth, can I, 

 From herbs, no remedy supply. 



It having been stated that the solution I have recommended above 

 "cannot be applied to the outside of most insects (especially 

 Libellulae), without, in course of time, injuring their colours," I 

 request attention to the few following observations : There are two 

 grand distinctions to be made in the colours of insects. Those 

 colours which originate from without, as in the moths and butterflies, 

 remain unimpaired in pristine splendour after death, until they are 

 destroyed by force or by accident. On the other hand, those colours 

 which have their source from within, and proceed from moist sub- 

 stances, gradually fade after the death of the insect ; and, in some 

 cases, even totally disappear, when the substances from which they 

 drew their origin have become dry and hard. By long experience, 

 I know that the colours of insects which are produced internally, as 

 in the red dragon-fly of Guiana, cannot be made permanent by any 

 process after the death of the insect ; but those colours can be re- 

 newed with great and durable effect. Suppose your correspondent 

 were to take an English dragon-fly (which I must inform him I have 

 never dissected), and sever the head from the thorax, the thorax from 

 the abdomen, and then subdivide the abdomen at every third ring, 

 this would enable him to clear away all the moist internal parts, from 

 whence the colours draw their source. A nearly transparent shell 

 would remain ; and he would only have to introduce into it colours 

 similar to those which the insect exhibited in life, after having washed 

 it well with the solution. The joining again of the dissected parts 

 would complete the process. All this appears difficult ; still, it may 

 be effected. I have read somewhere of a Frenchman who could 

 harness a flea : I myself have dissected the Cayenne grasshopper, 

 and renewed its colours with great success. In 1808, after dissecting 

 the bill of the toucan, I completely succeeded in renewing the blue, 

 which had been removed by the knife ; and I believe the specimen 

 which I produced was the first ever exhibited in its renewed colours 



2 L 



