In the tropics, the Honey bee is replaced by the Meliponas and Trigonas. They are minute, stingless bees, which store up honey and live in colonies often of immense extent. The cells of Melipona are hexagonal, nearly approaching in regularity those of the Hive bee, while the honey cells are irregular, being much larger cavities, which hold about one-half as much honey as a cell of the Humble bee. "Gardner, in his travels, states that many species of Melipona build in the hollow trunks of trees, others in banks; some suspend their nests from the branches of trees, whilst one species constructs its nest of clay, it being of large size." (F. Smith.) In a nest of the coal-black Trigona (Trigona carbonaria), from eastern Australia, Mr. F. Smith, of the British Museum, found from four hundred to five hundred dead workers, but no females. The combs were arranged precisely similar to those of the common wasp. The number of honey-pots which were placed at the foot of the nest was two hundred and fifty. Mr. Smith inclines to the opinion that the hive of Trigona contains several prolific females, as the great number of workers can only be thus explained, and M. Guerin found six females in a nest of the Tawny-footed Melipona (M. fulvipes). At home, our nearest ally of the true Honey bee, is the Humble bee (Bombus), of which over forty species are known to inhabit North America. The economy of the Humble bee is thus: the queen awakens in early spring from her winter's sleep under leaves or moss, or in the last year's nest, and selects a nesting place, generally in an abandoned nest of a field-mouse, or beneath a stump or sod, and "immediately," according to Mr. F. W. Putnam,[2] "collects" a small amount of pollen mixed with honey, and in this deposits from seven to fourteen eggs, gradually adding to the pollen mass until the first brood is hatched. She does not wait, however, for one brood to be hatched before laying the eggs of another, but, as soon as food enough has been collected, she lays the eggs for a second. The eggs are laid, in contact with each other, in one cavity of the mass of pollen, with a part of which they are slightly covered. They are very soon developed; in fact, the lines are nowhere distinctly drawn between the egg and the larva, the larva and pupa, and again between the latter and the imago; a perfect series, showing this gradual transformation of the young to the imago can be found in almost every nest. [Illustration: 15. Cell and Eggs of Bombus.]