Observations on the behaviour and abundance of Tineola bisselliella and
Tinea pellionella were made during 1942 and 1943 in a Brisbane wool store which
remained relatively undisturbed for more than three years. The store contained
c. 10,000 strongly compressed. jute-covered "double dumps" of low-grade, greasy
wool, stacked in large bays separated by passages. Microclimatic conditions were
more equable than in the open and very favourable to the moths. Substantial
vertical gradients in temperature and relative humidity resulted from insolation
of the roof, but there was little horizontal differentiation. The wool tended to
buffer fluctuations of these elements, both in the free air spaces and, still more,
within the dumps.
Larvae of Tinea were confined to loose wool protruding through breaches
in the jute pack. Tineola occurred both there and within the surface 2 in. of the
compressed wool under the pack. By 1943 there was estimated to be an average
of c. 50 well-grown larvae per dump. Adult moths could always be seen sitting or
running on the dumps throughout the stacks.
The moth populations were studied by sampling with tanglefoot traps in
the passages and stacks. Both species had a flight period around dusk, about half
the 24-hr catch being made during the 3 hr after sunset. The peak fell earlier on
cool evenings. A regression of activity on mean flight period temperature was
established, a rise from 65 to 80�F doubling the catch. Females rarely fly: they
normally constituted only c. 0.3 per cent, of the catch, although the sex ratio in
the population as a whole was probably about 23 : 19 for Tineola and 13 : 49 for
Tinea. The density of moths in flight was approximately equal in stacks and
passages at a, given level, but usually increased with height.
By correcting the daily catches for the effect of temperature on activity,
plots of adult abundanoe against time were constructed. The two species fluctuated
in almost identical fashion. Numbers were low in winter, high in spring and summer,
with an indication of two to three generations per annum. From the beginning of
1943 a great decline in abundance set in, the peak for that year being a small fraction
of that for 1942.
The braconid Apanteles carpatus, a parasite of both moths, was also taken on
the traps. It had a flight period at about the time of the daily temperature maximum.
A regression of activity on temperature showed a near-quadrupling of the catch for
a rise from 70 to 85�F. A plot of adult abundance was derived as for the moths.
It showed a single seasonal peak falling after the moth peaks. Several overlapping
generations are postulated. The abundance ratio of Apanteles to moths rose steadily
from spring to autumn in each year, but showed close agreement for corresponding
seasons of the two years: there is no reason to ascribe the 1943 decline in moth
numbers to the parasite.
A spider, Uloborus geniculatus, became very abundant during 1943 and is
believed to have been responsible for the decline of the moths, which represented its
main source of food. Over the relevant period the percentage of female moths in the
catch increased 40-fold, presumably as a result of the differential removal of the
active males by the spider. It is calculated that in this way the number of males
was reduced, by November 1943, to about 1/45 of what it would otherwise have
been. The spider probably also caught adult Apanteles.
It is concluded that, apart from effects of the introduction of additional
species, the moths and spiders would ultimately establish some sort of equilibrium,
probably at a rather low level of density. The factors favouring Uloborus in its
limiting role are discussed.
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