BIOLOGY OF THE AUSTRALIAN TORTOISE BEETLE TRACHYMELA-TINCTICOLLIS (BLACKBURN) (CHRYSOMELIDAE, CHRYSOMELINI, PAROPSINA), A DEFOLIATOR OF EUCALYPTUS (MYRTACEAE), IN SOUTH-AFRICA
Gd. Tribe et Jj. Cillie, BIOLOGY OF THE AUSTRALIAN TORTOISE BEETLE TRACHYMELA-TINCTICOLLIS (BLACKBURN) (CHRYSOMELIDAE, CHRYSOMELINI, PAROPSINA), A DEFOLIATOR OF EUCALYPTUS (MYRTACEAE), IN SOUTH-AFRICA, African entomology, 5(1), 1997, pp. 109-123
An Australian tortoise beetle, Trachymela tincticollis (Blackburn), wa
s discovered near Cape Town in 1982 on severely defoliated Eucalyptus
gomphocephala DC trees. By 1985 it had spread 800 km to Port Elizabeth
. Bath adults and larvae feed on the new leaves of 13 Eucalyptus speci
es cultivated in South Africa, including the important commercial spec
ies E, grandis Hill ex Maiden. Females laid an average of 11 eggs per
day from mid-August to the end of December. Eggs were laid at dusk in
fissures 0.5-1.0 mm wide in the bark of the host tree and the number o
f batches laid per day was largely determined by the amount of food av
ailable. Larvae hatched after four-and-a-half days and hid in fissures
near their feeding sites during the day. They had a bimodal activity
pattern, feeding just before sunrise (93 %) or after sunset (7 %). The
re were four larval instars before pupation in the soil below the host
tree. Larvae were active from September to February with a peak in nu
mbers in November which was synchronous with the annual leaf-flush of
the host trees. Total development time from egg to adult emergence was
35 days. The sex ratio was approximately 1:1. Various traps were used
to monitor the phenology of the different life stages. Adults flew at
canopy height and dispersed mainly in February and March. This study
formed part of a successful biological control programme in which the
introduction of the egg parasitoid Enoggera reticulata Naumann (Hymeno
ptera: Pteromalidae) achieved a parasitism rate of 96 %.