MUSEUM OF NATURE Insect studies strengthen continental drift theories

Press, Volume CXIV, Issue 33448, 1 February 1974, Page 14

MUSEUM OF NATURE Insect studies strengthen continental drift theories

One of the most exciting' recent geological theories suggests that New Zealand was once part of a massive southern continent named Gondwanaland. This continent comprised what is today South America. Africa, India, Australia, New Zealand and Antarctica. The theory is even more convincing when we find that the outlines of these continents today fit together quite neatly like a jig-saw puzzle.

Gondwanaland broke up into the separate continents about 140 million years ago, isolating New Zealand before land dinosaurs, mammals and snakes could reach it. This accounts for the absence of mammals and snakes from our fauna today.

At the same time, according to these theories, New Zealand underwent a period of great mountain emergence: it is difficult to comprehend that our shoreline once extended northwards beyond Australia to New Caledonia before being

'Contributed by the Canterbury Museum)

eroded and reformed into the shape it is today. This connection between New Zealand and New Caledonia accounts for the remarkable similarity between the fauna of the two islands, despite the great expanse of sea that now separates us. Recently, as museum entomologists (insect specialists), we paid a seven-day visit to New Caledonia to search for a family of caddis-flies found also in New Zealand. The importance of this group — the subject of several previous museum articles — lies in its food value to trout and other fresh-water fish. To search for these insects our party travelled inland to some of the remote and fastflowing mountain streams. Here, if it were not for the tropical climate, the atmosphere could easily be mistaken for that of our New Zealand bush. Insects remarkably similar to ours are seen moving through the vegetation, while birds resembling our fantail and bellbird sing in the trees above. The illusion is made even more complete by the presence of our native long-tailed and shining cuckoos, which migrate to the island to avoid New Zealand’s winter. Our efforts were rewarded

when we found the larva or grub stage of our caddis flies on the rock surfaces of these fast-flowing mountain streams. Here they construct a delicate funnel-shaped web of silk which filters food from the water. Each grub builds a small retreat of sand grains directly behind the net. The whole structure is a spectacular feat of engineering.

To identify these insects correctly both the larvae and winged adults must be collected. Unfortunately th? adult stage is often difficult to find and capture, since most are nocturnal and seem to vanish completely during the day.

However we made use of the attraction insects have for lights and by means of a special mercury vapour light bulb run off a small petrol generator, a number of adults were collected.

Although a number of previously undiscovered insects were collected, perhaps the most exciting find was several groups of caddis-fly known only in New Zealand The presence of almost identical relatives in New Caledonia further reinforces the theory of ancient land connections between the two countries. — R.A.S.