who are working on one side from the fifty or sixty at work on the other.  Unless they have a sight which can pierce the most opaque bodies, neither can see what is doing on the other side.  Nevertheless, a bee on one side does not dig a hole or add a fragment of wax which does not correspond exactly with a protuberance or a cavity on the other side.  How do they contrive to do this?  How does it happen that one does not dig too far, and the other not far enough?

How is it that every angle coincides in such magnificent perfection?  Who tells the bee to begin here and to end there?  Once again we must be satisfied with the reply that does not answer:  “It is one of the mysteries of the hive.”  Huber has tried to explain it by saying that at certain intervals, by the pressure of their feet or their teeth, they produce a slight projection of the wax on the other side of the comb, or that they can determine the thickness of the block of wax by its flexibility, its elasticity, or some other physical property which it may possess; or, again, that their antennae are able to serve as compasses in enabling them to examine what is going on in the darkness of the other side; or, last of all, he suggests that all the cells mathematically derive their shape and dimensions from those of the first row, which is built without the need of further concert on the part of the workers.  But one can easily see that these explanations are not sufficient; the first are guesses which cannot be verified; the others simply change but do not remove the mystery.  But if it is good to change a mystery as often as possible, it is never good to flatter one’s self that to change it means to remove it!

WASPS

(FROM THE NATURALIST IN NICARAGUA.)

BY THOMAS G. BELT, F.G.S.

[Illustration]

I one day saw a small black and yellow banded wasp hunting for spiders; it approached a web where a spider was stationed in the centre, made a dart towards it—­apparently a feint to frighten the spider clear of its web; at any rate it had that effect, for it fell to the ground, and was immediately seized by the wasp, who stung it, then ran quickly backwards, dragging the spider after it, up a branch reaching to the ground until it got high enough, when it flew heavily off with it.  It was so small, and the spider so heavy, that it probably could not have raised it from the ground by flight.  All over the world there are wasps that store their nests with the bodies of spiders for their young to feed on.  In Australia, I often witnessed a wasp combating with a large flat spider that is found on the bark of trees.  It would fall to the ground, and lie on its back, so as to be able to grapple with its opponent; but the wasp was always the victor in the encounters I saw, although it was not always allowed to carry off its prey in peace.  One day, sitting on the sandbanks on the coast of Hobson’s Bay, I saw one dragging along a large