I 



THE ENTOMOLOGIST, 133 



M. Capronnier was entrusted with canying out these expevi- 

 tnenls, and the paper referred to contains his report. 

 Everyone knows that among the Lepidoptera it is the green 

 and carmine colours which are most rapidly destroyed by 

 daylight. M. Capronnier wished to ohtiiin insects of the 

 year's hatching, but could only obtain sufficient qiuintilies of 

 Euchelia Jacobeae, L. The inferior wings of this insect are 

 of a deep carmine, uniform in tone, — an important point in 

 the experiments. The principal colours of the solar spectrinn 

 are the yellow, the red, and tlie blue. M. Capronnier rejected 

 the red as giving a tint too dark, and added the mixed 

 colours, violet and green. He had thus four tints chosen 

 with the same degree of tone, and of a moderate shade — 

 yellow, violet, green, and blue, besides a colourless glass. He 

 made five small square boxes of '08 centimetres square and 

 1 centimetre in depth ; the whole surface was covered with 

 one of the above-mentioned glasses. Each wing was fixed in 

 the middle of the box, and floated in a bath of very bright 

 light, but protected from the rays of the sun. Each of the 

 wings was partly covered by a band of black paper, and their 

 position was so arranged as to leave exposed successively 

 each of the parts during a period of fifteen, thirty, and ninety 

 days. The following are the results: — Colourless glass. — 

 After fifteen days of exposure the carmine tint was visibly 

 attacked ; after thirty days the alteration was more sensible ; 

 and after ninety da}s the work of destruction had rapidly 

 advanced, and the carmine had passed into a yellowish tint. 

 Blue. — With this tint the same alterations took place as in 

 the case of colourless glass. Green. — This colour preserved 

 the carmine during the first fifteen days; a change was 

 indicated on the thirtieth day ; and on the ninetieth the 

 alteration was marked. Yellow. — During the ninety days 

 the yellow alone left the carmine colour almost intact. 

 M. Capronnier says almost, for a slight alteration in the tint 

 could be noticed at the end of the ninety days. This last 

 observation proves that there is no absolute preservative, and 

 that collections must be kept in darkness, under penalty of 

 seeing them seriously changed at the end of a given time. 

 Neveitheless, it is evident fiom the above that the yellow is 

 the best preservative against alterations in the colours of 

 insects. iNI. Capronnier consequently concludes that a 



