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NOTES AND QUERIES
The foodplant, Aristolochia tagala Champ, or the India Birthwort, is a poisonous vine and, in our experience, is the sole host to the larvae. It has been identified in both the areas mentioned above and numerous plantings have been made by us in pots, gardens and other areas—the plant growing readily from seeds. It is, however, relatively slow growing and since a mature caterpillar will consume a whole leaf of approximately 100 cm2 in 24 hours we consider this a factor in the population variations that occur.
In 1967 and 1968 sightings became more numerous, many larvae being found and bred. Females were seen ovipositing and the insect was bred through from the egg to the imago on many occasions. Corbet and Pendlebury (3), while mentioning that it has been bred in Malaya on a few occasions, state there appears to be no record of the life history. In 1969, a full-blown population explosion took place and the butterfly became very common in the known areas. Sightings also occurred throughout the New Territories and also, for the first time, Hong Kong Island.
There are four main broods extending from April to October, and by the third brood in August 1969 the vines were stripped of leaves and females were laying on adjacent plants regardless of species. We thinned out the caterpillars, destroying some and breeding as many as we could support on our artificially grown vines. The interesting observation was made that eggs not deposited on Aristolochia tagala but subsequently transferred to our potted plants and reared, had a high incidence of parasitism. While parasitism is a common mechanism of population control in many other butterflies, we consider the exhaustion of the host plant the most important factor in the limitation of the numbers of T. helena. At the expected time of the last brood in October none could be seen. At the time of writing the butterfly is still to be seen in reduced numbers and the vines are slowly recovering.
Marsh states that the larva is a brownish red; but it could more accurately be described as dark plum in colour in the second and third instars, and shortly before pupation occurs is a beautiful dove-grey, the legs being black and the tubercles tipped with red. The pupa if disturbed makes a convulsive movement and emits a distinct squeak or hiss which is obviously intended to frighten predators. The adults when netted often remain motionless in the bottom of the net due, it is thought, to catalepsy induced by the sudden shock of capture.