354

r DYEING AND CALICO PRINTING.

abdomen of the inseds becomes surrounded by a viscous transparent liquid,which glues them to the plant, and which, continuing to be secreted, formsa cellule surrounding the animal. The substance composing this celluleis the stick-lac. The cellule attains its full size in March, and the insedthen exhibits the appearance of a red oval-shaped, smoothly-polished, lifelesssack, entirely filled with a beautifully red liquid; its size is then about thesame as the full-grown cochineal. So it remains for some months, untilin Odober the liquid will be found to contain twenty to thirty young inseds.The old inhabitant of the cell dies, and the young brood leave the cell bypiercing the top. The stick-lac when carefully viewed will be seen to containthe pierced, empty, somewhat hollow cells. The young brood is so closelypacked together that out of a number of six only one finds room to constructits cells by being enabled to pierce the twigs of the trees; the remaininginseds die or are devoured by birds. The young twigs of the trees, which areinhabited by the inseds, appear as if dusted over with a red powder, and thepresence of the insed causes the death of the twigs by exhaustion. Theinseds are carried from one tree to another by the feet of birds.

When an incision is made in the softer branches of any of the trees uponwhich this insed lives, a milky juice exudes, which coagulates instantaneously,yielding a glutinous material, which after drying resembles stick-lac. Thestick-lac of commerce is chiefly gathered along the hilly banks of the Ganges,and in sufficient quantity to supply all demands. The stick-lac best suitedfor dyeing purposes should exhibit a deep red colour; the pale-coloured per-forated kind is only fit for varnish-making, because it does not contain theinseds. The stick-lac covers the branches of the trees to a thickness of somemillimetres, the cellules being placed longitudinally. Their diameter is5 millimetres, and each contains the carcase of a dead insed. The resinobtained from this material is amber-coloured, and is known as shellac. Wedo not know whether the lac is secreted by the animal after it has beenmodified by passing through its organs, or whether it is diredly produced fromthe vegetable parenchyma of the tree by the piercing of its bark by the insed.

In India the lac, that is to say the resin, is applied by the natives for variousornamental purposes, viz., the making of bracelets, neck-chains, and the like;also as sealing-wax, and for preparing varnish. In Europe it is used fordyeing and varnish.

Shellac, the main constituent of our sealing-wax, is, as already noticed,produced by the insed, but the shape it is met with in trade is due to artificialpreparation.* The tree known as Celastrus ceriferus, a native of India andthe warmer part of China, and producing a wax largely used in these countriesfor candle-making, supports an insed of the same kind known as Coccusceriferus. The Chinese cultivate this insed, and it yields a waxy red-colouredsubstance, known as pela.t Of stick-lac the following varieties occur:—

i. Stick-lac in sticks gathered in March and Odober. The cellules arefastened to the twigs upon which they were formed. It is a hard, dark red,transparent resin, which shines when broken ; if chewed it colours the saliva

* Kerr, “ Phil. Transadions,” lxxi., 1781, p. 374, Figs. 1 to 6. Kerr, “ Roxburgh Transac-tions,” Ixxxi., p. 228. “ Asiatic Researches,” ii., 1799, p. 361. Virey, “ Journal Complexdu Didt. des Sc. M6d.,” x., 1821, 193, Figs. 1 to 7.

t “Anderson, “ Monographia Cocci Ceriferi,” 1791. Pearson, in “Phil. Transactions,1794 . P- 383*