. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 248 ZOOLOGY They suck the juices from stem and leaf. Plant lice have a remarkable life history. Early in the year eggs develop, into wingless females, which produce living young, all females. These in turn reproduce in a similar manner, until the plant on which the}' live becomes over- crowded and the food supply runs short. Then a generation of winged aphids is produced. These fly away to other plants, and reproduc- tion goes on as before until the approach of cold weather, when males and
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 248 ZOOLOGY They suck the juices from stem and leaf. Plant lice have a remarkable life history. Early in the year eggs develop, into wingless females, which produce living young, all females. These in turn reproduce in a similar manner, until the plant on which the}' live becomes over- crowded and the food supply runs short. Then a generation of winged aphids is produced. These fly away to other plants, and reproduc- tion goes on as before until the approach of cold weather, when males and females appear. Fertilized eggs are then produced which give rise to young the following season. The aphids exude from the surface of the body a sweet fluid called honeydew. This is given off in such abundance that it is estimated Maple scale, tive adults if au aphid Were the size of a cow it would iVom°'photorr^h S'^^^ ^^^ thousaud quarts a day. This honey- eniarged twice, by dew is greatly esteemed by other insects, es- pecially the ants. For the purpose of obtaining it, some ants care for the aphids, even providing food and shelter for them. In return the aphid, stimulated by a stroking move- ment of the antenna of the ant, gives up the honeydew to its protector. Some aphids are extremely destructive to vegetation. One, the grape Phylloxera, yearly destroys immense numbers of vines in the vineyards of France, Germany, and The Order Hymenoptera This order contains some of the most highly developed insects. We have already learned something of the structure and habits of the bees, in connection with the study of the pollination of flowers. Let us now find out about their wonderful communal life. In the order Hymenoptera are placed bees, ants, and wasps, insects which have developed a complicated social life. In connec- tion with this communal life, nature has worked out a division of. Please note that these images are extracted from scanned page images that may h
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