V. HUGHES SKCKETIONAKY COVERING OF DACTVI.OPIUS. 141 



APPENDIX 11. 



THE CHEMICAL ANALYSIS OF THE SECRETIONARY COVERING OF 

 DACTYLOPIUS PERNICIOSUS. 



By Frank Hughes, Chemist to the Khedivial Agricultural Society. 



The scale [scale here means both the insects and their ovisacs — F. C. W.] 

 contains a small amount of wax w^hich can be separated by solution in boiling 

 alcohol, or better, petrol. From solution in the latter it yields^ after 

 recrystallization, a considerable proportion of a hard wax melting at 8 3° '5 

 and having a density of 0*970 at 15° C. This is in all probability Ceryl 

 cerotate. There is present a mixture of waxes of lower and indefinite melting- 

 point. 



ThQ fibrous material of the scale [ = ovisac] is insoluble in water or alcohol^ 

 but easily soluble in dilute alkali, from which solution it is precipitated by 

 acids. Its properties agree very closely witli those oi fibroin. 



Cane sugar is present in considerable amount in the " honey dew/' as well 

 as a trace of reducing sugar. 



A colouring matter of a reddish crimson is present. This can be extracted 

 with water, or better, alcohol. In the latter solvent the absorption spectrum 

 resembles, though it is not identical with, that of cochineal. Acids have 

 little eifect on the colour nor has ammonia ; it is, however, changed to a 

 brownish green by the addition of a large excess of alkali. 



