Contents - LAC Biosafety

332 Insect pests in plantations: case studies
Fig. 10.39 Characteristic skeletonization of teak leaf caused by Eutectona machaeralis.
known to be very variable in E. machaeralis, and may depend upon the season.
Temperature and humidity are believed to influence the colour pattern; light
forms have been produced experimentally at high temperatures and dark forms
at low temperatures, from the same ancestors (Beeson, 1941). In view of such
variability, a more detailed taxonomic study on specimens from India,
Indonesia, Malaysia, Myanmar and Thailand is necessary to resolve the species
identities.
The moth has a wing-span of 19–26 mm, the males being slightly bigger than
the females. Forewings are white to ochreous yellow, with distinct or indistinct
pink to crimson zigzag markings; hindwings are paler, with an ochreous or
reddish marginal line or band. The full-grown larva is 20–25 mm long. The head
is light brown and the body is greenish to brown or purplish, with two pairs
of black dots surrounded by a white or yellow margin on each segment.
Longitudinal, brown, yellow or green bands appear on the sides in later instars.
Life history Moths rest during the day in shaded places in the undergrowth,
especially dry leaves on the ground. Beeson (1941) observed that females
often predominate in wild populations and are often twice as numerous as
males. This needs verification as data reported by Gopakumar and Prabhu (1981)
show that the sex ratio was more or less even in pupal samples collected from
teak plantations at Kulathupuzha in Kerala, India in June, September and
December. They found an early preponderance of females in the emerging
moths, probably an adaptation to prevent inbreeding. However, according to
Beeson (1941), a female-dominant strain of the insect occurs in Myanmar.
Females are ready to mate on the night of emergence but males do not mate
until the third night after emergence. In the laboratory, moths feed on sugar