66
THE ESSEX NATURALIST.
resumed work again about 8 a.m. the next day, and speedily
completed her task.
The record time taken, from the introduction of the Methoca
to the Tiger Beetle larva till the shaft was filled up, was one
hour. Usually it was about an hour and a half. There were
always some periods of waiting after the stinging of the larva,
perhaps so as to allow the full effects of the poison to take place.
After the egg was laid the rest of the work proceeded with the
greatest energy, and unless interrupted by the lateness of the
hour it was carried out without a pause.
From the 26 eggs laid by this female were obtained 20
cocoons. In the remaining six cases two of the eggs did not
hatch, while four of the Tiger Beetle larvae died before the full
growth of the Methoca larvae, which then died also.
On July 23rd the second female emerged, and at once started
to lay a series of unfertilised eggs to the number of ten. She
was then permitted to pair and proceeded to lay another series
of ten eggs.
From the first series I obtained eight cocoons and from the
second only four.
It was getting late in the season, and it became more and
more difficult to get Tiger Beetle larvae of suitable size. Some
that I had in store were getting ready for pupation, and I
think this may have had some influence on the large mortality,
but further investigation is required to test this conjecture.
On August 11th I went to Epping Forest to hunt for more
Tiger Beetle larvae. I saw in the ground a hole which I thought
looked like that of a rather small specimen, and inserted a thin
grass stem for the larva to grasp with its jaws. On pulling
it up I was much surprised and delighted to find a female Methoca
hanging on to the end of the stem instead of the expected Tiger
Beetle larva. She was rather small, but a further search
revealed another and larger female running over the ground.
From the latter I got three eggs, which have this summer
produced two males and one female.
The spring of this year (1930) was cold and the emergence
of the imagines did not begin till August, and the results were
very disappointing. A large number of the larvae in the
cocoons are apparently lying through their second winter.
The most successful results were from the eggs deposited by