THE ENTOMOLOGIST. 133 
M. Capronnier was entrusted with carrying out these experi- 
ments, 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 obtain insects of the 
year’s hatching, but could only obtain sufficient quantities of 
Euchelia Jacobee, Z. 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 spectrum 
are the yellow, the red, and the 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 days 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. Yel/ow.—During the ninety days 
the yellow alone left the carmine colour almost intact. 
M. Capronnier says a/most, for a slight alteration in the tint 
could be noticed at the end of the nivety 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. 
Nevertheless, it is evident from the above that the yellow is 
the best preservative against alterations in the colours of 
insects. M. Capronnier consequently concludes that a 
