158 CAROTINOIDS AND RELATED PIGMENTS 



believes that this sexual difference is related to the ability of the 

 females to impart the blood pigmentation to the eggs, for protective 

 purposes, an idea previously proposed by Poulton, who also noticed 

 the pigmentation of the eggs. Although the writer is not in sympathy 

 with the protective notions regarding animal colorations, believing that 

 such phenomena are to be explained entirely on physiological grounds, 

 and not through theories built upon the assumption that colors impart 

 the same sensations upon the retina of the eyes of lower animals that 

 they do upon our own, it is nevertheless an interesting fact that insects 

 apparently have the ability to impart the derived pigments found in 

 the blood to their eggs just as is found in the case of the higher ovi- 

 parous animals. 



Rrjnchota. Among this group of insects, usually called bugs, red, 

 yellow and green colored species are commonly encountered. Caroti- 

 noids are to be expected because the insects are mostly phytophagous. 

 Among the Aphids, or plant lice, the green colors are undoubtedly 

 derived from the food as in the case of caterpillar larvse, as Mao- 

 chiati (1883) first pointed out, Sorby's (1871c) study of this green 

 pigment showed, however, that the yellow pigments accompanying 

 chlorophyll are also present, and may be extracted from the crushed 

 insects with carbon disulfide. The two well-marked absorption bands 

 in the blue shown by these extracts, at once classifies the pigment 

 among the carotinoids. Sorby, himself, called the pigment aphidolu- 

 teine. The pigment of some red aphids may not be carotinoid, be- 

 cause Sorby found that the red color of aphids which he found on 

 apple trees could be extracted with hot water, the extract turning 

 yellow on addition of acetic acid, and red again when ammonium 

 hydroxide was added. The properties of the pigment suggest an 

 anthocyanin-like substance. 



Red coloration in the tegument- among some species of bugs, is 

 unquestionably carotinoid at times, perhaps carotin itself. Thus, 

 Physalix (1894) extracted the red pigment of the hemipter, Pyrrho- 

 coris apterus, from two liters of the insects. The pigment was deep 

 red in carbon disulfide, yellow in alcohol and ether, gave the lipo- 

 chrome reaction with con. H 2 S0 4 , and showed the absorption spectra 

 of carotin. Physalix asserted that the pigment was carotin or a very 

 closely related substance. 



Coleoptera. Green and yellow and red pigments also characterize 

 the tegument of the beetles. Ley dig (1876) first noticed the autumn- 

 like changes in the color of the green beetles Cassidce and the species, 



