Today we have not only intensive cultivation and lowered disease-resistance of most plants, but many other factors contributing to a lessening of what might be termed biological control of diseases. The balance of nature is being disturbed. There is less smoke from factories than in former years, but buildings of greater height and in greater numbers particularly blocks of flats have brought more shade and draughts. Man and his domestic cat have reduced the garden-dwelling birds by killing and fright. The use of E605, DDT, and the gamma isomer of BHC (Lindane) as sprays kills all sorts of insects, whether they are pests or not. But we have developed a bad habit of regarding all insects and grubs as pests. Many of them are priceless friends, for they feed on destructive creatures. Without them we would be quite powerless in controlling diseases, despite all our sprays and dusts. It is highly important that we learn to know our friends from our foes, even in the garden. These friends fall into two main groups insects and birds.

Insects

Of the insects the most useful are the green lace-wing, the syrphid or hover-fly, most wasps, the ladybird, and the mantids or praying mantis.

The larva of the dainty green lace-wing fly (Chrysopa ram-burii) is often called the aphis lion because of its habit of preying upon this pest. The larvae are drab in colour, slender, and about one-third of an inch long. They have very active legs and a pair of large toothed jaws. They are easy to find at night among aphides or prowling over rose plants in search of food, which also includes scale insects. In the daytime they usually hide among the petals of blooms. The fly is a beautiful light green with delicately patterned lacy wings and conspicuous bright-yellow eyes. Great numbers fly or rest round lights at night in warm weather.

The hover-fly or syrphid (Syrphus viridiceps), in the caterpillar or maggot phase of its life cycle kills a tremendous number of aphides. This larva is grey-green, About one-third of an inch Broad. It some what resembles the harmful leaf-curling caterpillar, but differs in that it moves slowly, does not attempt to escape or conceal it self when touched, is harder, and little broader. It is most common is spring and autumn.

Wasps vary greatly in their life histories; some are almost fantastic. The female of some species has, at her rear end, a long, then, sharp append age called an ovipositor. She injects this into her prey, which she has already stupefiled, and there deposits her eggs. On hatching, the larvae feed the body tissues of the host unil fully grown, when the host dies and the larvae emerges as insects. One minute wasp lays her egges within the aphis. As the larva grows the aphis skin becomes hard and metallic in appearance. That aphis is past doing harm to roses and shelters a young wasp, precious to the garden, for it will very soon deposit an egg within the body of each of hundreds of aphides. Never destroy aphides that have this unusual appearance. Other species stun, impregnate with ova, and remove caterpillars several times their own weight.

The spotted ladybird beetle (Lets conformis), lays its eggs on aphis-infested plants, and the young (often called "niggers"), on hatching, despite their small size, will destroy aphides at the rate of thirty or forty an hour.

The mantids are always given credit for destruction of pests. There are many species varying in colour from green to brown, and in size from half an inch to three inches in length. Some of the smaller types attack aphides. The larger varieties destroy bees and other desirable insects just as commonly as beetles, moths, and flies. They even resort to cannibalism. The egg-cases, found on almost any structure or hard-wooded plant, are small, brown, rectangular mounds with sloping sides. The upper aspect is marked by two rows of small circular indentations. Each of these is the covering of a cell containing an egg. The young mantid forces its way out through the disk.

Since modern insecticides have been used for spraying in the last few years, it is noticeable how some garden pests that are not killed by them have increased in numbers, especially red spider and pea mite. This is due to these compounds killing insects that are enemies of these pests.

Birds

From a rose-grower's point of view there are no undesirable birds. It is doubtful if any exist even in the orchards. Destruction of birds of any sort is probably a great disservice to us all. Some may do harm, but they do a great deal more good. Others render us wonderful service in distant parts. For instance, the notorious louse-infested ibis regularly destroys enormous numbers of grasshoppers daily during the late spring.

The silver-eye (Zosterops coerulescens) Plate 52 is represented by five species in Australia. It is often called the "blight bird", because of the vast numbers of aphides it consumes. It is also the chief enemy of case-moth larvae. The damage done by these birds to fruit is far outweighed in the same orchards by their good work earlier in the spring.

The house sparrow (Passer domesticus), especially while very young, ranks second only to the silver-eye as an aphis-killing bird.

The yellow-tailed thornbill, or tomtit (Acanthiza chrysorr-hoa) a friendly little bird, though essentially insectivorous can often be induced to feed on crumbs from one's hand. The bright-yellow feathers at the base of its tail are visible only when the bird is disturbed. It is very agile in flight

The blue wren {Malurus cyaneus) Plate 52 , so well known to us all, shows a distinct partiality for the cockchafer larva, eating as many as eighty a day for months in succession. It also kills small grasshoppers, winged insects, and caterpillars.

Among our particularly useful birds we should also name the harmonious thrush, the blackbird, the starling, the black-faced cuckoo shrike, the little cuckoo shrike, the swallows, and the scarlet-breasted robin.

All bird-life should be encouraged in the garden, and should be tempted in every possible way to become less timid of man. Food tables and water receptacles for bathing and drinking attract large numbers of birds. They must be placed out of reach of cats where possible, otherwise well out in a clear space where cats will not be able to make an ambush. It is very pleasing to wander in one's garden and be approached by small birds in search of crumbs of bread, biscuit, or cake. If poison baits of bran must be laid for cutworms, it is essential that they be cleared away very early next morning to minimize the chance of birds being poisoned. Actually very few insectivorous birds feed on the ground and so these baits are not as dangerous as one might imagine.

If you have not already a bird bath in your garden, why not obtain one? Not only will hundreds of useful friends come to drink and bathe, but you will have many hours of entertainment and amusement as you watch their varied forms of behaviour. Starlings bathe most vigorously, as if to belie their reputation for being dirty creatures. Quite commonly half a dozen of them will be in the bath together, splashing large quantities of water well beyond the bath, so that within a very few minutes two or three gallons have been scattered. They then spend some minutes on a nearby bough, shaking their feathers. The wrens and tits seem to scorn bathing completely, and the minah does not indulge often. The green-eyes rarely alight on the bath, but with frequent repeated sorties they furtively flip the surface of the water. The sparrow is loath to wet much more than his feet except on rare occasions. The blackbird and the thrush, with their beautiful plumage, make most attractive sights while bathing. They are, too, amongst the most frequent visitors to the bath, and remain there for long periods.

See that the bath is at least eighteen inches in diameter, holds several gallons of water, is no more than three inches deep, is in a quiet part of the garden, and is on a pedestal at least three feet high as a precaution against cats. For the same reason, place the bath well clear of trees and large shrubs. Moisture loving plants, such as azaleas, do well with the frequent splashing.

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