PDF - CES (IISc)

LICHENS AS FOOD 399
A minute organism, Hymenobolina parasitica 1
, first described by Zukal
and doubtfully grouped among the mycetozoa, feeds, in the plasmodium
stage, on living lichens. The parasitic habit is unlike that of true mycetozoa.
It has recently been recorded from Aberdeenshire.
b. INSECT MIMICRY OF LICHENS. Paulson and Thompson 2
give instances
of moth caterpillars, which not only feed on lichens, but which take on the
coloration of the lichens they affect, either in the larval or in the perfect
moth stage. "One of the most remarkable examples of this protective
resemblance to lichens is that of the larva of the geometrid moth, Cleora
/ichenaria,\\\\ich feeds upon foliose lichens growing upon tree-trunks and
palings, and being of a green-grey hue, and possessed of two little humps
on many of their body-segments, they so exactly resemble the lichens in
colour and appearance as to be extremely difficult of detection." Several
instances are recorded of moths that resemble the lichens on which they
settle : perfect examples of such similarity are exhibited at the Natural
History Museum, South Kensington, where Teras literana, Moma orion, and
other moths are shown at rest on lichen-covered bark from which they can
hardly be distinguished.
Another curious instance of suggested mimicry is recorded by G.E. Stone 3 .
He spotted a number of bodies on the bark of some sickly elms in Massa-
chusetts. They were about of an inch in diameter " with a dark centre
and a drab foliaceous margin." They were principally lodged in the crevices
of the bark and Stone collected them under the impression that they were
the apothecia of a lichen' most nearly resembling those of Physcia hypoleuca.
Some of the bodies were even attached to the thallus of a species of Physcia;
others were on the naked bark and had every appearance of lichen fruits.
Only closer examination proved their insect nature, and they were identified
as belonging to a species Gossypina Ulmi, an elm-leaf beetle common in
Europe where it causes a disease of the tree. It had been imported into
the United States and had attacked American elms.
'It is stated by Tutt 4 that the larvae of many of the Psychides (Lepi-
doptera) live on the lichens of trees and walls, such as Candelaria concolor,
Xanthoria parietina, Physcia pulvenilenta and Buellia canescens, and that
their larvae pupate on their feeding grounds. Each species makes a "case"
peculiar to itself, but those of the lower families are usually covered exter-
nally with grains of sand, scraps of lichens, etc. The " case " of Narcyria
inonilifera, for instance, is somewhat raised on a flat base and is obscured
with particles of sand and yellow lichen, giving the whole a yellow appearance.
That of Luffia lapidella is roughly conical and is held up at an angle of 30
to 45 when the larva moves. The "cases" of Bacotia septum are always
upright; they measure about 5-5 mm. in height and 275 mm. in width and
1 See also p. 267.
- Paulson and Thompson 1913.
3 Stone 1896.
4 Tutt 1900, p. 107.