Revision as of 10:04, 29 June 2016

Scale Insects

“Scale Insects” is the name given to insects belonging to the family Coccidae of the order Homoptera. They receive this name from the production by the females of a secretion, which often hardens and forms a protective scale beneath which the insect lives; but some species, such as mealy bugs, are invested with a waxy secretion and a true scale is wanting. Scale insects include a number of serious plant pests; on the other hand, some species have a commercial value, notably the Chinese insect Coccus pela, the Japanese insects Ceroplastes spp., the cochineal insect Coccus cacti, the lac insect Carteria lacca, and the so-called ground pearls of the genus Margarodes.^[1].

Family Coccidae

There are a number of genera of the family Coccidae that furnish waxes, although only two have been of economic importance thus far, namely Coccus ceriferus, the source of the Chinese insect wax of commerce, and Tachardia Lacca, furnishing "stick-lac" wax or, in its refined form, commercial shellac wax.

In the family Coccidae there is a subfamily Coccinae, in which the "scale" is merely the thickened surface of the insect, instead of being a separate housing of the body. The Pulvinaria is a genus which secretes a mass of waxy cotton-like material in which the insect places the eggs. The genus (Coccus belongs to the Coccinae, as do also Brahmea, Tachardia, Cerococcus, and Pulvinaria. These insects are referred as "coccins."

The scale insects that have a wax shell housing separated from the body are known as “coccids”. Ceroplastes is the best known genus; others furnishing waxes are Iceria, Sasakiaspis, Prontapsis, and Tachardina. The character of the wax changes somewhat, depending upon the species of host plant on which the insect feeds; in the Far East these plants are privet, citrus fruit, tea, etc. Most of the wax studies have been made in India, China and Japan. The eggs deposited by the scale insects may be transferred from one host to another to secure the best commercial yields, as in the case of the Coccus ceriferus and the ceroplastids.^[2].

References

1. ↑ Warth, A. H.; The Chemistry and Technology of Waxes. Reinhold Publishing Corporation. Second Edition, p. 104
2. ↑ Warth, A. H.; The Chemistry and Technology of Waxes. Reinhold Publishing Corporation. Second Edition, p. 104