The hibernating female wasps are roused into activity by the warmth of early spring and commence to seek out likely situa tions for their nests. Vespa vulgaris, germanica anti rufa make underground nests, other species suspend their nests from bushes, trees, etc., while Vespa crabro (the hornet) nests as a rule in hollow trees. In the very common species V. vulgaris and ger manica, the nest is commenced by layers of "paper" being applied to the roof of the cavity in the ground destined to contain it. From the centre of the disk thus formed a stalk is provided and upon its widened free end the first few cells are constructed: they are hexagonal in form, open below and closed above. An umbrella-like covering is formed around the roof of the cavity to protect the comb and an egg fixed at the upper end of each cell by means of a cement, which prevents it from falling out. In a few days, according to temperature, the larvae hatch and are fed with chewed or malaxated portions of caterpillars, flies or other insects until fully grown. Prior to transforming to the pupa the larva 'spins a cocoon within the cell and closes the mouth of the latter with a tough floor of silk. The wasp grub now evacuates the contents of the gut for the first time and soon changes into a pupa. After four to six weeks from the time of egg-laying the adult wasps bite their way through the floors of the cells and emerge. These early individuals are all workers and they very soon take over the whole business of feeding the brood and ex tending the nest, so as to leave the queen free to devote her self solely to egg-laying. When the nest is fully formed it is more or less spherical externally and is invested by several pro tective coats of "paper": once a layer of comb has attained its full dimensions, new layers are built below and interconnected by vertical pillars. This goes on until about seven or more tiers of comb are constructed, and an average sized nest contains about 5,000 wasps towards the end of the season. In addition to the normal occupants a number of other insects inhabit wasps' nests either as inquilines or parasites and in the soil of the earthen chamber beneath the nest fly larvae live on the waste organic residue accumulated there.
Following this brief sketch of the habits of social wasps certain fundamental aspects of their behaviour remain to be mentioned. The feeding of the brood with malaxated portions of insects has already been referred to : the hungry grubs in the comb thrust out their heads, as Wheeler remarks, "like so many nestling birds," eager to attract attention from their nurses. It is now established that the activities of the latter are by no means disinterested and in return for the food supplied to their grubs, the wasps them selves eagerly imbibe the sweet saliva emitted from the mouths of their young. They stimulate the grubs by contact, or even by seizure of their heads between their own jaws, if the desired secretion be not forthcoming. This reciprocal feeding is termed "trophallaxis" which, as will be seen later, is of very general sig nificance in the behaviour of social insects.
Owing to this expenditure of saliva by the larvae and the great number which are reared simultaneously, many are in adequately nourished and pupate as small individuals with poorly developed ovaries. In this manner it is claimed that the work ers are produced, while the exigencies of collecting food for the larvae and caring for the nest is exhausting labour, which tends to keep them sterile. It is only later in the season that the abundance of workers and the amount of food brought in, allow of the larvae being more copiously fed, many of which in conse quence develop into fertile females.
flowers with exposed nectaries, the maxillae and labium are short as in wasps, but in the social and other specialized forms which visit tubular flowers with deeply seated nectaries, these same organs are greatly elongated, the ligula being drawn out to form the so-called tongue. The under surface of the latter is provided with a groove so overlapped by special hairs as practically to form a tube. Along this channel the nectar is sucked into the pharynx whence it passes into the crop or storage chamber of the gut. Here it becomes mixed with a ferment, presumably derived from the salivary glands, which converts its cane-sugar into invert sugar (dextrose and levulose). In this changed form the nectar is known as honey and it is regurgitated and served as food for the brood. The adaptations for collecting and gathering pollen are pronounced : the whole surface of the body is densely hairy and many of the hairs are branched or plumose so as to retain pollen grains until the insect combs them off by means of its legs. The pollen is collected in masses and attached to the outer surfaces of the tibiae and first tarsal joint of the hind legs. These parts of the bee are broadened and fringed with long hairs to form a pollen-basket or corbicula. Another important feature is the production of wax, all social bees utilizing this material for comb building and it is formed as a secretion which is discharged from glands between the abdominal segments where it hardens into lamellae.
The most primitive of the true social bees are the Bombidae or bumble bees. About zoo kinds are known and they are char acteristic of temperate regions while in the tropics they are gen erally found in the mountains.
The societies of true bumble bees (Bombus) in Europe and North America are in most respects parallel to those of the social wasps of those regions, in that the fertilized females or queens, produced at the end of summer, hibernate and found new colonies in spring. On the advent of mild weather each queen seeks out a spot for her future nest which commonly consists of fine grass or moss formed into a hollow ball and located rather deep in the ground : some kinds, known as "carder bees" form surface nests concealed among herbage. Having formed the nest itself, the queen proceeds to gather a mass of pollen which is mixed with honey into a paste. Upon the top of this mass she constructs a circular wall of wax and in the cell thus formed she lays the first batch of eggs, afterwards capping it over with wax. She also constructs a waxen receptacle or honey pot which is filled with a store of honey for her own consumption, while she is brooding over the eggs to incubate them. The larvae hatch in about four days and feed immersed in their bed of pollen-paste and up to this stage the queen behaves much like a solitary bee. A signifi cant change, however, supervenes and she gnaws a hole in the lid of the cell and regularly supplies her young with regurgitated honey and pollen, thus practising progressive provisioning. About the tenth day after egg-laying the larvae spin tough yellow co coons and on the twenty-second or twenty-third day the first worker bees appear. New cells become added to the nest, each cell containing about a dozen eggs, and when sufficient workers have emerged the work of provisioning devolves upon them and the queen becomes confined to the nest. The workers construct additional receptacles for honey and pollen or store these substances in the empty cocoons : further new cells are added to the nest and the latter at its period of maximum strength contains from about i oo to 500 bees. Later in the season some of the larvae, enclosed in the larger cells, and derived from fertilized eggs, are abundantly fed and develop into females which subsequently hibernate : males, which develop from unfertilized eggs, appear about the same time. The workers do not differ from the queens except in size, and since they have been more or less inadequately fed during the exigencies of the earlier life of the colony, they are consequently smaller : any eggs laid by them are unfertilized and develop into males.