And first let us find out how the sexes are arranged.
It is not possible to ascertain the chronological order of a laying, except by going to suitably-chosen species.

Fortunately there are a few species in which we do not find this difficulty: these are the Bees who keep to one gallery and build their cells in storeys.

Among the number are the different inhabitants of the bramble-stumps, notably the Three-pronged Osmiae, who form an excellent subject for observation, partly because they are of imposing size--bigger than any other bramble-dwellers in my neighbourhood--partly because they are so plentiful.
Let us briefly recall the Osmia's habits.

Amid the tangle of a hedge, a bramble-stalk is selected, still standing, but a mere withered stump.
In this the insect digs a more or less deep tunnel, an easy piece of work owing to the abundance of soft pith.

Provisions are heaped up right at the bottom of the tunnel and an egg is laid on the surface of the food: that is the first-born of the family.