Lac insect and its uses

1. BY
A.Maria selva francis
II M.Sc Zoology

2.  Lac is yet another useful product obtained from insect.
 It is a resinous secretion and unique in that it is only
one of animal origin.
 All scale insects secrete a hard encrustation over their
body and the secretion of the lac insect.
 Kerria lacca takes the form of a brown resinous
substance and it is the true lac from which shellac of
commerce in manufactured.

4. Lac insects

5.  Under natural conditions the insect is found growing on
a large number of trees in India and Myanmar.
 The important lac producing countries are India and
Thailand.
 India produces about 42000 tonnes of lac which is
about 65% of the wordl’s total output.
 Small quantity of lac are produced in T.N, Andhra,
Karnataka, Maharashtra,& Punjab.

6.  The female insect lays eggs inside the encrustation.
 They hatch almost immediately and the nymphs crawl
out of the cell.
 Encurstation the nymphs may continue to emerge for
two or three weeks but most of the nymphs come out
during the first five days.
 A single female can produce 300 to 1000 nymphs.
 The nymphs are minute, about 0.6 mm long, soft
bodied, pointed posteriorly, deep red in colour with
black eyes.

7. Encrustation

8.  Even during early stages the male and females cells are
distinguishable since the former has grown up in its
longitudinal axis and is slipper-shaped and the latter
has grown up in its vertical axis and is spherical
shaped.
 Thus the female insect are the chief producer of lac.
 Egg laying ceases when the temperature inside the lac
cell falls bellow 17⁰C and the nymph becomes inactive
at temperatures below 20⁰C.

9.  Lac cultivation can be carried out in forest and
subforest areas where suitable host tees grow.
 Places with annual rainfall of about 75 cm with
moderate temperatures are quit suitable
 The success otherwise of lac cultivation depends
mostly upon climatic conditions.
 The host plants for the lac insect, palas (Butea
monosperma), Kusum (Schleichera oleosa) and ber
(Zizyphus mauritiana).
 Ber is not a lac host of any importance except in West
Bengal and Punjab.

10. Host plant lac insects

11.  Palas is a good host but dose not grow well in
unsuitable area. It occurs throughout India except in
T.N, Karnataka, and Kerala.
 Kusum, through a small tree comes up well in hilly and
jungle areas and it produces best quality.
 There are two srains of the lac insect, the strain that
thrives on Schleichera oleosa (Kusum) called Kushmi
strain,all other host is known as Rangeeni strain.

12.  Rangeeni grown an Shorea tolura in Salem area and
Karnataka gives three crops in 13 months. About 90%
of lac produced in India comes from rangeeni srain.
 In an area all the host trees should not be continuously
cultivated with lac as this will have deleterious effects
on the vigour of the trees.
 Trees are divided into convenient coupes and cultivated
by rotation .
 By this system trees have sufficient rest to put forth
new shoots and they also give sustained lac yields
regularly.

13.  Brood lac obtained from the previous crop of the
particular strain.
 Brood lac should be cut from the parent tree neither too
soon before the crawlers are ready to emerge out nor
very late when swarming has already commenced.
 The best indication of the right time of cutting brood
lac is when the lac cell is red in the anterior half and
orange in the anal region.
 Selected brood lac branches are cut into sticks of 15 –
30 cm.

15.  They are tied by means of a banana or jute fibre either
single or in bundles of two or three sticks each and
either longitudinally or interlaced between two host
branches.
 Inoculation is to be done on a non rainy day.
 The crawlers start moving out in one or two days after
inoculation.
 The brood lac sticks need to be removed within three
weeks of inoculation as otherwise the enemies of lac
insect may spread from brood lac to fresh crop.

16.  Lac is marketed by shellac. It is manufactured
manually and involves three stages viz, ‘crushed lac’,
‘seed lac’, and ‘shellac’.
 The lac encrustations are disloged from the branches
either by twisting them with hand, scraping with a knife
or by feeding the branches through rollers as in a cotton
gin, the space between the two roller so adjusted that
only the encrustations are disloged.
 The scrabing should be done as immediately as
possible after harvest to avoid damage by predator.

17.  The scrapped material is known as raw lac, scrapped
lac, or stick lac and it should be left in the sun for long.
 If there is any necessity for long storage it should be
done after fumigation with sulphur.
 The stick lac is disintegrated and the powdery material
is called crushed lac.
 It is then immersed in water in stone or cement tubs for
three days and often stirred well
 The supernatent crimson coloured liquid is drained off.
The material is then transferred to large vats to which
lime is added at the rate of 1kg / day of 160kg material.

18.  Now the lac dye settles down and is collected. The
bites of twigs, fibrous materials and parts of insect
body that float in the vats are removed.
 The suspended lac is filtered through cloth. The process
is repeated thrice or four times.
 The material is spread in cement floor and allowed to
dry. It is called the seed lac or grain lac.
 Shellac is manufactured either by large scale solvent
extraction process which is adopted by large factories
or by hot melting method which is adopted by small
manufactures.

19.  In some cases rosin like colophony is added up to 12%
to lower the melting point.
 Colouring is given by addition of arcenic sulphide. The
balanced material is put in cloth bag of about 9m long
& 0.6m and diameter and heated over an open fire or
furnace rotating the bag constantly.
 The lac melts and oozes out of the bag. When sufficient
quantity of molten lac has collected outside the bag,
 The bag is twisted and the lac is quickly dropped to
clean cement floor or transferred to glazed porcelain
surface of hot water cylinder.
 It is orange to pale yellow in colour.

20.  Button lac is manufactured by pouring the molten lac
into dyes in a zinc sheet instead of stretching for shellac
preparation.
 This results in buttons of lac 7 cm diameter and 0.6 cm
thick.

21.  Seed lac and shellac find many uses in industry and in
ayurvedic medicine
 They are used in manufacture of french polish and floor
polish, gramophone records, bangles and printing inks,
electrical insulators and sealing wax which contains
about 35% lac in addition resin, turpentine ect.
 It is used in painting wooden toys, shellac mixed with
colouring matters and kept ready as rods of different
colour.
 The shellac is also used for filling hollow ornaments,
for painting sides of ships, for preventing leakage of
water

22.  In ayurvedic medicine lac is widely used both for
external application as well as for internal
administration.
 Powdered shellac mixed with honey is a specific
remedy for haemostasis.
 As a drug lac has germicidal, febrifuge and astringent
properties.
 Lac dye contains some nitrogen and therfore, can be
applied to fields as a manure. It is used for dyeing eri
silk which takes a beautiful red colour.
 Production of lac in India has widely fluctuated over
years from 24000 – 65000.