[The accompanying figure represents a completed hornet's nest as it appears when suspended from a beam. Hornets often choose for their home the space between the roof and the ceiling of summer-houses, and the nests that are made in such localities are mostly large and handsome. The reader should notice the blisters by means of which the insect enlarges its habitation.] When hornets make choice of a tree for their domicile, they select one which is in a state of decay, and already partly hollowed; but they possess the means, in their sharp and strong mandibles, of extending the excavation to suit their purposes; and Réaumur frequently witnessed their operations in mining into a decayed tree, and carrying off what they had gnawed. He observed, also, that in such cases they did not make use of the large hole of the tree for an entrance, but went to the trouble of digging a gallery, sufficient for the passage of the largest hornet in the nest, through the living and undecayed portion of the tree. As this is perforated in a winding direction, it is no doubt intended for the purpose of protecting the nest from the intrusion of depredators, who could more easily effect an entrance if there were not such a tortuous way to pass through. [Illustration: Hornet's Nest in a hollow tree.] [Here is an illustration of a hornet's nest as it appears in the hollow of a tree. Industrious as is this insect, it never takes needless trouble, and alters its nest according to circumstances. As has already been seen, the combs are defended by a complete cover when the nest is placed in an open situation. But when it is built in the hollow of a tree there is no cover at all, the insect evidently knowing that the wooden wall with which the cells are surrounded, affords a sufficient protection. In cases where a cover is made, the hornets do not form only a single entrance, as is the case with the wasp, but have a large number of small entrances in different parts of the wall. Some of these entrances can be seen in the illustration on page 93. Hornets are in one sense more industrious than wasps. When night falls, the wasps betake themselves to their home, and sleep throughout the night. But, if the moon be up, the hornet is sure to work throughout the entire night, and will often do so, even when no moon is visible.] * * * * *