Footnote 29: Their daily life may be easily watched in the schoolroom, by means of one of the many good and cheap observation hives now made to be placed in a window frame. Directions for making a small observation hive for school work can be found in Hodge, _Nature Study and Life_, Chap. XIV. Bulletin No. 1, U. S. Department of Agriculture, entitled _The Honey Bee_, by Frank Benton, is valuable for the amateur beekeeper. It may be obtained for twenty-five cents from the Superintendent of Documents, Union Building, Washington, D.C. [Illustration: Cells of honeycomb, queen cell on right at bottom.] The cells of the comb are built by the workers out of wax secreted from the under surface of their bodies. The wax is cut off in thin plates by means of the wax shears between the two last joints of the hind legs. These cells are used to place the eggs of the queen in, one egg to each cell, and the young are hatched after three days, to begin life as footless white grubs. The young are fed for several days, then shut up in the cells and allowed to form pupae. Eventually they break their cells and take their place as workers in the hive, first as nurses for the young and later as pollen gatherers and honey makers. We have already seen (pages 37 to 39) that the honeybee gathers nectar, which she swallows, keeping the fluid in her crop until her return to the hive. Here it is forced out into cells of the comb. It is now thinner than what we call honey. To thicken it, the bees swarm over the open cells, moving their wings very rapidly, thus evaporating some of the water. A hive of bees have been known to make over thirty-one pounds of honey in a single day, although the average is very much less than this. It is estimated from twenty to thirty millions of dollars' worth of honey and wax are produced each year in this country. Cochineal and Lac.--Among other products of insect origin is cochineal, a red coloring matter, which consists of the dried bodies of a tiny insect, one of the plant lice which lives on the cactus plants in Mexico and Central America. The lac insect, another one of the plant lice, feeds on the juices of certain trees in India and pours out a substance from its body which after treatment forms shellac. Shellac is of much use as a basis for varnish. Gall Insects.--Oak galls, growths caused by the sting of wasp-like insects, give us products used in ink making, in tanning, and in making pyrogallic acid which is much used in developing photographs. Insects destroy Harmful Plants or Animals.--Some forms of animal life are of great importance because of their destruction of harmful plants or animals. [Illustration: An insect friend of man. An ichneumon fly boring in a tree to lay its eggs in the burrow of a boring insect harmful to that tree.]