-MUSEUM OF NATURE

Press, Volume CVIII, Issue 31582, 20 January 1968, Page 17

-MUSEUM OF NATURE

Monarch Butterfly

(Contributed by the Canterbury Museum)

Every summer the Museum receives excited inquiries about a large black and orange butterfly. (“Four inches! I’ve never seen anything like it before!”)

Its popular name is the Monarch butterfly, but in some countries it is appropriately called the Wanderer. Thought to have originated in North or perhaps South America, it has succeeded in migrating to and establishing itself in almost all tropical, sub-tropical and temperate lands. It was first recorded in New Zealand about 1840, in Tonga and Samoa in the 1800 s

and in Australia about 1870. In New Zealand, it was quite rare until, about 30 years ago, nature-lovers began to grow suitable food-plants especially to encourage it. Nowadays, wherever the milkweed shrub and the so-called swan-plant are grown in sufficient numbers, the caterpillars, fat two-inch creatures conspicuously ringed with cream and black, are fairly common. Dr A. W. B. Powell’s description of the shining inch-long chrysalis cannot be bettered—“a pale jade casket with a circle of gold-like specks near the top.” Many insects winter in the egg or in the larval stage. Not so the Monarch. In the North American autumn, for example, the adults fly from C. nada southwards all the way to California, a journey of more than 1000 miles.

There they hibernate on cypress and pine trees. In spring they disperse northwards again. The most astonishing thing about this hibernation is that certain individual trees are chosen as roosts year after year, and there will usually be many thousands of butterflies on each tree. Indeed, the hibernating Monarchs of California are quite a celebrated tourist attraction. In our own country, certain trees in Nelson are used by the wintering Monarchs in the same way, though the insects occur in very much smaller numbers. Did the Monarch achieve its present almost world-wide distribution unaided? Could it, for example, really have flown the Tasman, a non-stop flight of 1100 miles or so? On its annual migration flights over land. It might of course touch down for a rest at intervals, but it seems unlikely that it could do this at sea. One thing is known for certain: Monarchs have been observed as much as 400 miles from the nearest land, flying strongly. Besides, we know of another wanderer of similar size, the Blue Moon butterfly, small numbers of which appear in New Zealand almost every summer. The male is particularly striking in appearance, each velvet-black wing ornamented with just one electrioblue circle enclosing a white spot. We may be almost sure that the Blue Moons fly here from Australia where they are not uncommon. If they were breeding here, the caterpillars could not have escaped notice for long.—J.G.P. The photograph shows a Blue Moon butterfly (top) and a Monarch.