. Botanic Garden at Kandy.]

HYMENOPTERA. _Mason Wasp_.--In Ceylon as in all other countries, the
order of hymenopterous insects arrests us less by the beauty of their
forms than the marvels of their sagacity and the achievements of their
instinct. A fossorial wasp of the family of _Sphegidae_,[1] which is
distinguished by its metallic lustre, enters by the open windows, and
converts irritation at its movements into admiration of the graceful
industry with which it stops up the keyholes and similar apertures with
clay in order to build in them a cell. Into this it thrusts the pupa of
some other insect, within whose body it has previously introduced its
own eggs. The whole is surrounded with moistened earth, through which
the young parasite, after undergoing its transformations, gnaws its way
into light, to emerge as a four-winged fly.[2]

[Footnote 1: It belongs to the genus _Pelopaeus, P. Spinolae_, of St.
Fargean. The _Ampulex compressa_, which drags about the larvae of
cockroaches into which it has implanted its eggs, belongs, to the same
family.]

[Footnote 2: Mr. E.L. Layard has given an interesting account of this
Mason wasp in the _Annals and Magazine of Nat. History_ for May, 1853.
"I have frequently," he says, "selected one of these flies for
observation, and have seen their labours extend over a period of a
fortnight or twenty days; sometimes only half a cell was completed in a
day, at others as much as two. I never saw more than twenty cells in one
nest, seldom indeed that number, and whence the caterpillars were
procured was always to me a mystery. I have seen thirty or forty brought
in of a species which I knew to be very rare in the perfect state, and
which I had sought for in vain, although I knew on what plant they fed.

"Then again how are they disabled by the wasp, and yet not injured so as
to cause their immediate death? Die they all do, at least all that I
have ever tried to rear, after taking them from the nest.

"The perfected fly never effects its egress from the closed aperture,
through which the caterpillars were inserted, and when cells are placed
end to end, as they are in many instances, the outward end of each is
always selected. I cannot detect any difference in the thickness in the
crust of the cell to cause this uniformity of practice. It is often as
much as half an inch through, of great hardness, and as far as I can see
impervious to air and light. How then does the enclosed fly alw