Reminders of spring in the hedges

Press, 20 September 1985, Page 18

Reminders of spring in the hedges

Country Diary

Derrick Rooney

For a reminder of spring it hasn’t been necessary in the last couple of weeks to look beyond the hedge, where honey bees have been as busy as beavers gathering pollen from a stray pussy willow. The bumble bees are settling to a food-gathering routine, too. A month ago lots of short-tongued queens were out looking for nest sites, exceptionally early. They didn’t find the nest box tucked away under a tree at the bottom of the garden but they must have been successful elsewhere because there are hardly any queens about now, most of the bumble bees in the last week or two have been foraging workers. Soon the long-tongued queens, which are always later to appear, will be flying and it will be time to move the nest box to a likely site. This kind ,is the more useful of the bumble bees, because it pollinates quite a number of. flowers that honey bees have problems with. Contrary to common belief, you canitell the difference between the wo kinds by size but By the

number of stripes on the abdomen and thorax, and by the way the stripes are arranged. The large bees that you see early in the spring are mostly queens; later they are likely to be mostly workers hatched from nests at their most active and vigorous stage. When the nest is just beginning or just tapering off the workers tend to be small. They all have a fairly short life span, estimated to be about three weeks, except the queens. Only the young queens, in hibernation (usually in dry sites such as burrows under tree roots) live through the winter. The other occupants of the nests die in autumn. Aphids are now numerous, too, for so early in the spring, probably as a consequence of the mild winter which has raised their survival rate. There have even been one or two of their predators, ladybirds, out and about early from hibernation this month. New Zealand has several species of ladybird, in red, yellow, and orange with varying numbers of black spots which are apparently one of the clues to their identification (don’t ask me what the others are). Occasionally you see a black one, with yellow spots. rd always thought these were a sepiarate species, but now it appears they are just a colour form of the common ladybird. I’d jdso noticed that on my plants buck

ladybirds appear mainly in autumn and spring, but I’d assumed this to be by chance. Recently, however, word came that scientists at two English universities have been looking at ladybirds and have found good reasons why the black ones appear mainly in the cooler months. These ought to have been obvious to anyone who has grown plants in black pots or planter bags. Black has the ability to absorb rather than reflect solar heat, so it’s hardly surprising that the English scientists found that on cool days black ladybirds have significantly higher body temperatures than ordinary red or yellow ones. I wish I’d thought of this first! The black females (scientists call them “melanistic”), interestingly, have better thermal efficiency than the males. They are able to breed successfully at much lower temperatures than their conventionally marked brothers and sisters, hence their appearance in the cooler months. They also, of course, emerge from hibernation earlier in spring. In the height of summer, high body temperatures constitute a definite disadvantage, so at hot times, while ordinary ladybirds are flying away home, the black ones are likely to be panting in the shade.

The next step for the scientists will be to analyse this phenomenon of melanism and do some genetic tinkering to extract the.gene or

whatever is responsible for the black epidermis, and graft it on to ordinary ladybirds, this creating a race of super-predators to go on eating insect pests year-round instead of confining their activities to the warm months as any sensible bug would do. One of the big chemical companies is already trying something similar with the thuringiensis bacillus which kills caterpillars on cabbage's. By genetically grafting toxins into the bacteria they hope to make it kill a much wider range of insect pests. I’m not sure I approve of this sort of meddling which certainly makes the oldfashioned straightforward poison-

ous chemicals seem more acceptable. While on the subject of spring, it’s interesting to note that scientists in North America have found that some flowers which appear early in the season have the ability to either generate or absorb large quantities of heat. Dark red camellias, for example, can absorb so much heat from the sun during the day that at night they can be as much as 12 degrees warmer than pale-coloured camellia flowers; that’s why red camellias survive frosts which brown off white ones. Some spring flowers can actually generate heat, warming their petals sufficiently to melt their way through snow. Some members of the arum family can raise their flower temperature as much as 22 degrees above that of the surrounding air. What’s more, some flowers in this family (known as aroids) are cunningly constructed so that whatever way the wind blows, a gentle air current which is just right for sucking in pollinating insects is directed to the depths of the flower, where the bits that matter are hidden. Many of the aroids are pollinated by blowflies and their flowers can omit a fearful stench. “Skunk cabbage,” a North American aroid, isn’t so called for nothing; but the Mediterranean “dragon lily,” which is huse and almost black, is the

most stinking plant I know. You can catch its stomach-twisting odour of carrion 40 or 50 feet away. But the scientists say it isn’t actually the smell which pulls in flies to these flowers — it’s the extra warmth, which also disseminates the stink. Subtle, eh. * * * The kowbai trees at the Rakaia Gorge the other day were in full bloom, in marked contrast to the last time we were there, in midwinter, when only a handful of trees showed colour. The kowhai is regarded by many New Zealanders as a national flower, with some justification, because the kowhai is found in almost all parts of the country and is a characteristic element in the New Zealand landscape. What most Kiwis don’t realise is that the kowhai is not exclusive to New Zealand. Trees which are recognisably the same species are found on the coast of Chile and even further away to the East, around Cape Hom on islands in the Atlantic Ocean. Other species in the same genus grow in the Northern Hemisphere. Still, we can probably claim all New Zealand kowhais as exclusively home developed. There are three main species — the North Island kowhai, which may be the most common in cultivation but has a fairly restricted distribution in the wild, tlxe prostrate kowhai,

and the common kowhai — plus a few oddballs which don’t yet fit any pigeonhole. Sharp-eyed travellers will have noticed that the common kowhai differs considerably in stature, conformation, flowering time and behaviour in different parts of the country. Some have tiny leaflets, some fairly large ones; some go through a tangled juvenile stage and some don’t; some take up to 20 years to flower from seed and some flower in two or three years. Some flower early in spring, and some flower late. The botanical theory developed to account for all this is that the common kowhai developed thousands of years ago as a result of natural hybridising between the prostrate kowhai and the North Island one. These are regarded as the original species, and the common kowhai as an ancient “speciating hybrid.” And how did it get to South America and beyond? Well, the kowhai seed is large and buoyant, with a very hard, impermeable outer skin, and is capable of floating or drifting in water currents for a very long time. Kowhai seeds also have a venerable life; they are known to be able to germinate after 10 years storage in ordinary room conditions, and can probably survive much longer. Amost certainly, kowhai seeds got to South America on ocean currents. a I recently saw living evidence in

support of this theory. A friend on a visit to the Chatham Islands picked up some kowhai seeds on a beach, and when he got home he germinated them. They were clearly from trees growing on the mainland in Canterbury (he showed me some seedings from Chathams trees for comparison). If kowhai seeds can get as far as the Chathams there isn’t anything else to stop them before they get to South America — barring, the odd American nuclear submarine or Russian trawler. It’s an attractive, if chauvinistic, thought that the oldest of the kowhai trees growing on Chilean beaches might very well be able to claim New Sealand citizenship. '