520 THE MICROSCOPE. 



most delicate fluids of the vegetable kingdom, is a spec- 

 tacle that must be regarded with the highest interest ; 

 especially when we remember that these dissimilar crea- 

 tures are all composed of the same elements, and that the 

 principal organs of the adult animal were in a manner 

 shadowed out in all its previous stages. 



Nor is the singularity of their natural history the only 

 claim that these insects have upon our attention. Lowly 

 as they seem in point of organisation, there are few 

 animals that exceed them in commercial importance. To 

 give an instance or two ; the finest red dyes known to our 

 manufacturers, are derived from insects. The Lecanium 

 ilicis, an inhabitant of the Ilex, Evergreen -oak, growing in 

 countries near the Mediterranean, was employed for this 

 purpose by the ancient Greeks and Romans, as it is still 

 by the Arabs ; and, until the introduction of the Mexican 

 cochineal, another species, the Coccus polonicus, living 

 on the roots of the Scleranthus perennis in Central Europe, 

 was much used for the same purpose. The Mexican cochi- 

 neal, which has driven all other kinds out of the field, is 

 the species Coccinia, represented in fig. 251 ; this was long 

 regarded as a parasite upon the Cactus opuntia, Prickly- 

 pear a plant common in Central America. The com- 

 mercial importance of this insect is shown by a single fact : 

 in 1850, no less than 2,514,512 Ibs. of cochineal were im- 

 ported into Great Britain alone (value about 7s. per Ib.) ; 

 and as about 70,000 insects are required to weigh a 

 pound, we may form some idea of the almost countless 

 numbers annually destroyed. For many years the culti- 

 vation, or rather feeding, of cochineal was entirely confined 

 to Mexico ; but the insect has lately been introduced into 

 Spain, and the French possessions in Africa, with every 

 prospect of success. A fourth species, of great import- 

 ance, is the Lac insect, Coccus lacca, an inhabitant of the 

 East Indies, where it feeds upon the Banian-tree, Ficus 

 religiosa, and other trees. It is to this insect we are 

 indebted, not only for the dye-stuffs known as lac-dye 

 and lac-lake, of which upwards of 18,000 cwts. were 

 imported in 1850, but also for the well-known sub- 

 stance called shell-lac, so much used in the preparation 

 of sealing-wax and varnishes. It is somewhat remark- 



