64
THE ESSEX NATURALIST.
It was made with ordinary glass tumblers, which took as
covers the lids of glass-topped tin boxes of 23/4 inches diameter,
with which they made a nice fit. Each tumbler contained a
pair of glass plates cut to. the slope of the tumbler and reaching
to within an inch of the top.
The glass plates were separated about 1/2 inch by damp
sand and were supported upright by more of the same material.
On one side this reached to the top of the glasses; on the
other, which may be called the front, it was only about two
inches up, level with a strip of glass placed horizontally in the
sand between them, which prevented the Tiger Beetle larva,
when introduced, from getting down out of sight.
In July, 1928, I found at Oxshott another Methoca female
running over the ground. Some larvae of Cicindela campestris
were obtained and each was established in a shaft made by a
glass rod in the sand between the glass plates and against the
front side of a tumbler-subterrarium, as above described.
I gathered no fresh details of the method of attack of the
Methoca, but was interested to see the operation of filling up
the top of the shaft after the deposition of an egg which I had
previously missed. She sometimes tried to pull the Tiger
Beetle larva towards the top of the shaft, and if successful in
getting its head to within about half an inch of the surface she then
began to bite off pieces of the earth around the inside of the
shaft and drop them down on the head of the quiescent larva.
She worked most diligently at this operation and her efforts
gradually raised her almost to the surface. She then came out
of the shaft and carried into it between her jaws small particles
of earth lying near at hand, and also scratched others down
with her feet. The top of the shaft was by this means com-
pletely disguised so that it was indistinguishable from the sur-
rounding area.
If the wasp did not succeed in getting the larva to the top
of the shaft she went up and started the filling-in operations,
but had a little more difficulty in getting the earth to form a
bridge across the opening as there was no support for it. The
damp sand particles, however, tended to hold together when
bitten off and the shaft was successfully closed.
Nine ova were laid during the next few days, and subse-
quently a cocoon resulted from each.