Spatial dynamics of teak defoliator (Hyblaea puera Cramer) - Cochin ...

6.2. METHODS
In this study, post emergence behaviour ofmoths was studied at the site of
emergence by establishing a floor-less cage within a teak plantation, when in
March 1993, nearly 92 ha of teak plantations at Kariem Muriem was under
infestation. A cage (3m x 2m x 2m) made of nylon net was established at a
suitable site in the plantation in the first week ofApril when the insect population
had reached the pupal stage. The ground within the cage was cleared of fallen
leaves. Pupae were collected from the nearby area and were sexed. A total of 160
pupae (100 female and 60 male) were placed on the floor inside the cage along
with fallen teak leaves so as to provide a relatively natural microenvironment for
the pupae. Once the moths started emerging, diluted honey was provided on
sponge as food. At hourly interval, observations were made on the number of
moths emerged and their behaviour. During night, a dim, red light was used to
make the observations. Observations were continued for a period of three days. A
trained field observer was employed to take observations from the cage when
simultaneous observations had to be made in the field. Some observations were
also made on the behaviour ofmoths emerging in the field, outside the cage.
The flight behaviour of moths was observed at Kariem-Muriem during
1993. Over a period ofone month period immediately following the emergence of
moths from an infestation which occurred on 20 th March, observations were made
on the movement of moths in the field. To assess the sex ratio, collections of
moths were made from aggregations that were found on ground or in flight. Since
it is known that mated females start to lay eggs within two days
(Sudheendrakumar, 1994), the females collected were individually reared for two
days to know whether they laid eggs. Absence of egg-laying was taken as an
indication ofabsence ofmating. Whenever counts ofmoths in flight were taken at
different sites at the same time, trained observers were deployed for the work.
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