340 THE MICROSCOPE. 



regarded as perhaps the most marvellous thing in nature ; although 

 recent researches have shown that the history of many of the lower 

 animals presents us with circumstances equally if not more wonderful, 

 nevertheless the metamorphosis of the higher insects is a phenomenon 

 which cannot fail to arrest our attention. To see the same animal ap- 

 pearing first as a soft worm-like creature, crawling slowly along, and 

 devouring every thing that comes in its way, and then, after an inter- 

 mediate period of death-like repose, emerging from its quiescent state, 

 furnished with wings, adorned with brilliant colours, and confined in 

 its choice of food to the miost delicate fluids of the vegetable kingdom, 

 is a spectacle that must be regarded with the highest interest; especially 

 when we remember that these dissimilar creatures 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 may be, in point 

 of organisation, there are few insects that exceed them in commercial 

 importance. The finest red dyes known to our manufacturers are de- 

 rived from these creatures. The Lecanium Ilicis, which inhabits the 

 Ilex Or evergreen oak of the countries round 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 Porphyrophora polordca, which lives on the roots of 

 the Sderanthus perennis in Central Europe, was much used for the 

 same purpose. The Mexican cochineal, which has driven the others 

 out of the field, is also a species belonging to this group, the Coccus 

 cacti (fig. 139), which lives as a parasite upon the Nopal, or Cacttts 

 opuntia — a plant very common in Central America. The commercial 

 importance of this insect is shown by the fact, that in 1850 no less 

 than 2,514,512 lbs. of cochineal were imported into Great Britain 

 alone (value about 7s. per lb.) ; and as about 70,000 insects are sup- 

 posed to be contained in a pound of this substance, we may form some 

 idea of the numbers annually destroyed. For many years the culti- 

 vation of cochineal was entirely confined to Mexico ; but the insect has 

 lately been introduced into Spain and the French possessions in Africa, 

 with some prospect of success. A fourth species, of great importance, 

 is the lac insect {Coccus lacca), an inhabitant of the East Indies, where 

 it feeds upon the Banian-tree (Ficus religiosa), and some other trees. 

 To this insect we are indebted, not only for the dye-stufis known as 

 Zac-c?2/e and lac-lake, of which upwards of 18,000 cwts. were imported 

 iu 1850, but also for the well-known substance called sIiell4ao, so 



