534 



ON THE DESTRUCTION OF NOXIOUS INSECTS BY MEANS 

 OF THE PYRETHRUM. 



BY C. WILLEMOT. 



Of all substances hitherto proposed for the destruction of noxious 

 insects, powders have been found the only ones that can he used to 

 advantage on account of their simple and easy method of application. 

 All such powders, too, which have been employed, so far as known, are 

 derived from the vegetable creation. It woidd occupy too great a space 

 to enumerate here all the plants used in the form of powder for this 

 purpose ; it will suffice to mention some which have been more parti- 

 cularly under observation. Among these are the straight-leaved pepper- 

 wort (Lepidium ruderale, Linn., and Thlaspi ruderale, Desfon), found 

 growing in uncultivated places and among rubbish around Paris. This 

 is used in Southern Dalmatia in the form of powder almost exclusively 

 for the destruction of fleas. In some parts of Southern Russia, espe- 

 cially in the Crimea, a plant very common in France, Aristolochia Clema- 

 titis, Linn, (common birthwort) is used exclusively to destroy bugs. 

 Sawdust of aromatic wood, particularly American cedar (Cedrela odo- 

 rata, Linn.), is largely sold for the destruction of insects, and, according 

 to some authorities, most of the powders sold in Paris for that purpose 

 are composed of that substance. But after using and experimenting 

 wiih them we have been fully convinced that the object cannot thus be 

 perfectly attained. Their action is feeble, or they merely stupefy, for a 

 time, the insect, which soon recovers its strength and sensibility to do 

 injury. 



The greater number of the plants which furnish the most satisfactory 

 means for the destruction of insects are of the genus Pyretlmm. Many 

 observers, considering the botanic resemblance (as well as similar pro- 

 perties of this genus) with kindred ones as certain chamomiles, the 

 Anthemis Cotula for instance, have pretended that such indigenous plants 

 (chamomiles) may specifically furnish a powder for destroying insects 

 equal iu every respect to the Pyreihrum. But accurate and detailed 

 experiments by ourselves and other competent observers refute such 

 assertion. All the efficacy of the Anthemis Cotula consists in rendering 

 the insects insensible for a time instead of destroying them. The 

 inhabitants of the regions of Europe and Asia, near the Caucasian 

 mountains, seem to have been the first to discover the properties of the 

 Pyrethrum, ami try on a large scale the powders obtained from these 

 plants. The species employed differ according to the different localities. 



It is easv to comprehend that the inhabitants of the Caucasus choose 

 for their use that kind which is most abundant in their own country. 

 Thus in Armenia they prefer the red Pyrethrum (P. Roseum, Biebers), 

 commonly called Lowizachek, or flea plant. 



The Persian powder which appears most extensively used is 



