OP ARTS AND SCIENCES. 2G5 



appearance of the red color, which was formerly coTered. If the 

 grasshopper or its wings are subjected to stronger heat, both pigments 

 disappear at the same time. Krukeuberg believes it to be very proba- 

 ble, after his experiments, that the light has a prominent influence 

 on the color of insects, and that the light turns to red the insects 

 which were green during the summer. Spectral analysis makes it 

 evident that the green color has no connection with chlorophyll. 



It is often denied by entomologists that food has any marked 

 influence on color, as it is observed that in many cases caterpillars of 

 the same species feeding on the same plant show very different colors, 

 as, for instance, many Sphingidoe, cankerworm, and others. 



Perhaps Coccus cacti derives its coloring matter from the cactus; 

 but I was puzzled to find that some grubs of a beetle from Peru, 

 preserved in alcohol, had colored the alcohol rather intensely with 

 cochineal color. I do not know whether they live on the cactus, but 

 it can hardly be presumed. Tiiat other insects prepare a coloring 

 matter is well known from the May-beetles in Europe. An umber- 

 brown color, good for use, was prepared from them by distillation, and 

 used at the end of the last century. Mr. G. B. Buckton * and Mr. 

 Sorby f have published very interesting notes and experiments upon 

 the coloring matter of the Aphides. The somewhat condensed con- 

 clusions are : — 



1. The purple coloring matter appears to be a quasi-living prin- 

 ciple, and not a product of a subsequent chemical oxidizing pro- 

 cess. Mounted in balsam or other preserving fluids, the darker 

 species stain the fluid of a fine violet. 



2. As autumn approaches and cold weather reduces the activity of 

 the Aphides, the lively greens and yellows commonly become con- 

 verted into ferrugineous red, and even dark brown, which last hue in 

 reality partakes more or less of intense violet or purple. These 

 changes have some analogy with the brilliant hues assumed by maple 

 and other leaves during the process of slow decay. 



3. Aqueous solution of crushed dark-brown and yellow-green varie- 

 ties of Aphides originate different colors with acids and alkalies. The 

 chief difference consists in an alkali changing the solution of green 

 Aphides into a gamboge-yellow, instead of a purple, as in the brown 

 Aphides. 



* G. B. Buckton : Monograph of the British Aphides, vol. ii. p. 167. 

 London, 1879. 



t Sorby : On the Coloring Matter of some Aphides. Quart. Journ. Microsc. 

 See. vol. ix. p. 352. London. 



