Mary has such a fascinatingly serious way of doing things that aren't serious at all. She has got the curious notion lately that many little people live among the grasses, the grass people she calls them, and that that is the reason there are so many very little white flowers coming up in my lawn. My own notion had been that some rascally seedsman had sold me unclean grass seed, but Mary's notion that the grass people are planting and raising these little flowers for their own special delectation is, of course, a much wiser one. So when we walk on the lawn, we go very slowly, and I have to poke constantly among the grasses with my stick as we move along so that the little people may know we are coming and have time to scurry away from under our great boots.

When we got out to the row of brooms, we found many of the soft white cushions on all the bushes. But some of them were torn and dishevelled. And in these torn masses many tiny round particles could be seen. These little black specks are simply eggs, insect eggs, as I told Mary, and soon she had discovered among them some slightly larger but still very small red spots which were waving tiny black feet and feelers about. They were of course the baby insects just hatching from the eggs.

"Does the mother lay the eggs in these little white cushions and then go away and leave them?" asks Mary.

"No, she stays right by them," I answer.

"But where is she then? I can't—Yes I can too," cries Mary in great triumph. "Here she is at one end of the egg cushion. She is a part of it."

"Well, no, not exactly," I have to say. "It is part of her, or rather she spins the cushion, which is really a sac or soft box of white wax, in which to lay her eggs. Something the way the spiders do, you know. Only their egg box is made of silk and usually fastened to a fence rail or on the bark of a tree and left there. But some of the spiders, the large, swiftly running, black kinds that live under stones, carry the silken ball with the eggs inside about with them, fastened to the end of the body. Well, this cottony cushion scale insect—that's its right name—keeps its waxen sac of eggs fastened to it, but as the egg sac is much larger than the insect itself, it can't run about any more, but has to stay for all the rest of the time until it dies in the spot where it makes the sac. However, as it gets all the food it wants by sticking its slender little beak into the broom or other plant it is on and sucking up the fresh sap, it gets on very well."

"But what makes some of the egg cushions—how pretty they are, too!—so torn and pulled open," asks Mary, who has listened to my long speech very nicely. She often gets impatient when I lecture for too many minutes together.

"That is for you to find out," I say. "There is a dreadful thing going on here if you can only see it. But a rather good thing too. Good for the broom bushes anyway, and as they are my broom bushes and I like their flowers, good for me."

Just then a very stubby, round-backed, quick little red beetle with black spots walked off a broom stem on to Mary's hand. She didn't scream, of course, nor even jerk her hand away. She may learn when she is older to be frightened when pretty, harmless, little lady-bird beetles walk on her. But now she likes all sorts of small animals, and is not afraid at all.

Mary is not at all slow to understand things, and when this hard-bodied little beetle, with a body like half a red-and-black pill, walked off the broom on to her hand, she guessed that he might have something to do with the torn-up egg cushions. So it didn't take her long to find another little beast like him actually nosing about in an egg sac and voraciously snapping up all the unfortunate tiny, red, black-legged baby scale insects. He ate the eggs, too, and seemed to take some bites at the mother insect herself, and then Mary found more of the lady-bird beetles, and still more. They were on all the broom bushes where the white cushions were. And so one of the dreadful tragedies going on in my garden was soon quite plain to Mary, and she was very sorry for the helpless white insects.

"Where did the red beetles come from?" she asked pretty soon.

"From Australia," I answered. "Or rather their great-great-grandparents did. These particular beetles were probably born right here in the garden, because a colony of them live here. But they couldn't if there were not some cottony cushion scale insects here too. For this particular kind of lady-bird beetle can't live on any other food—at least they don't—except this particular kind of scale insect and its eggs, which is surely a curious thing, isn't it?"

But Mary is so used to finding that the insects have extremely unusual and curious habits—that is, habits different from ours—that she doesn't get excited any more when I tell her about them. She does though when she finds them out for herself, which makes me wonder if I haven't wasted a good deal of time in my life giving lectures to students about things instead of always making them find out for themselves. And maybe I am wasting some more time now while I am writing!

"How did they come from Australia?" asks Mary. For she knows that Australia is several thousand miles away across the ocean from California, and lady-bird beetles do not swim. At least not from Australia to America. So I have to give Mary another informing lecture, and this is it:

"Years and years ago, there lived in some fragrant-leaved orange-trees in Australia some white cottony cushion insects whose life was untroubled by other cares than those of eating and of looking after the children. As each insect was fastened for life on the leaf or twig that supplied it with all the food it needed, which was simply an occasional drink of sap, and as the white insects always died before their children were born, neither of these cares was very harassing. On thousands of other similar fragrant-leaved orange-trees in Australia lived millions of other similar white insects. And for a long time this race of white insects enjoyed life. Those were happy days. But on a time there came into one of the trees a few small red beetles, who eagerly and persistently set about the awful business of eating the defenceless white insects. From this tree the red beetles, or the children of them, went to other trees where white insects lived, and with unrelenting rapacity and uncloyed appetite ate all the white insects they could find. And so in other trees; and finally, with years, the red beetles had invaded all of the thousands of fragrant-leaved orange-trees in Australia, and had eaten nearly all of the millions of white insects.

"One day a very small orange-tree was taken out of the ground in Australia and sent with many others across the ocean to California. On this small tree there were a few of the white insects. The little tree was planted again in California and soon put out many fresh fragrant leaves. The white insects were astonished and rejoiced that day after day went by without the appearance of any red beetles. The white insects increased in numbers; there were thousands of fragrant-leaved orange-trees in California, and in a few years there were millions of white insects in them. One morning a man stood among the trees and said, 'Confound these bugs; they'll ruin me; what shall I do?' and a man who knew said, 'Get some red beetles from Australia.' So this orange-grower, with some others, paid a man to go to Australia and collect some live red beetles. The collector went across the ocean, three weeks' steady steaming, and sent back a few of the voracious little beetles in a pill box. They were put into a tree in a California orange-orchard in which there were many cottony cushion scale insects. The red insects promptly began eating the white ones; and their children and grandchildren and great-grandchildren have kept up this eating ever since. And so the orange-growers never tire of telling how the red beetles (whose name is Vedalia) were brought from Australia to save them from ruin by the white insects (whose name is Icerya)."

Now there are not many cottony cushion scales left in California. A very promising colony of them seems to have sprung up in my Scotch broom bushes. But the red beetles have found their way there already, as Mary and I discovered to-day, and so we think that by the time the broom flowers come, there will be few white insects left in the bushes.