H 
Indian Forest Records. 
[Vol. VIII 
only (or mainly) on plants more or less afflicted with “ gummosis,” 
a disease involving an abnormal growth of gum-producing bacteria 
in the tissues of the plant; the suctorial activities of the insect, by 
removing the gum and the bacteria that produce it, thus actually 
promote the welfare of the plant by reducing the disease. 
“ The more ordinary view, to which I confess I still adhere, is 
that a diseased condition of the plant is in no way essential to its 
successful colonization by lac insects, whose sensory, suctorial, diges¬ 
tive, and secretory apparatus has in the course of several million 
years become fitted to find, extract, and digestively deal with certain 
compounds that are normally present in the sap and cambial layer 
of many plants, the plants being, in the ordinary sense of the word, 
the insect’s victims. If the larval lac insect finds itself on a branch 
(whose bark is not too thick to pierce) of any plant whose juice 
suits its digestion, it will, I believe, attack it, even though the plant 
itself may be perfectly healthy and vigorous. It is generally 
believed that if the number of lac insects on a tree be large, their 
combined attack may kill the tree, just as does that of any other 
ordinary “ pest There is in short no reason as yet to attribute to 
the lac insect any beneficent role, or to doubt that its attack tends 
to hurt rather than help its “host ” or victim. In other words, from 
the point of view of the tree ,the lac insect is a pest and not a physician, 
and no definite symbiotic tendency has yet been demonstrated. 
“ In this connection it is also appropriate to point out that our 
comprehensive ignorance of the insect’s physiology does not justify 
Mr. Mahdihassan’s assumption that lac is produced from the water- 
soluble gums present in the plant. Lac itself is far from being a 
simple substance, but is a complex of some half a dozen by no means 
simple compounds, and at least some of these compounds may very 
probably be derived from fatty acids and essential oils or terpenes 
rather than from gum. Until therefore the digestive and secretory 
physiology of the insect has been investigated, it is unprofitable to 
make any positive statements as to the genesis of lac.” 
A fact which at first sight seems somewhat remarkable is that 
the lac insect is able to pass through two generations in a single 
growing season of the host; for it seems a priori unlikely that the 
peculiar conditions necessary for the welfare of an insect with so 
involved a life-history as the lac insect could recur at two different 
