170
THE ESSEX NATURALIST
Figure 2 shows the more exact locations. It is impossible on
this figure to give a clear picture of the numbers obtained from
two of the districts in Colchester. True to the often remarked
localised distribution of this insect, two large concentrations were
found—at TL/9824 ("C.R.G.S.") and TL/9723 ("Shrub End")—
which between them accounted for 165 living individuals.
Hall (1961) pointed out that the results of his survey showed
that the males appeared about one week before the females in
both 1959 and 1960. This is borne out by the present survey:
(Records of dead individuals have been discounted from the above analysis)
As well as simply recording date, sex and locality, all the
individuals brought in for examination were measured, and the
living ones marked and released. 143 were released at C.R.G.S.
and 33 at Shrub End. Three systems of marking were adopted.
The first method was to glue small labels to the underside of the
abdomen. This was soon discontinued as although the labels did
not wash off, it was found that in some cases the beetles were
rubbing them off. The second method used was to mark the upper
surface with spots of paint. Towards the end of the survey it was
considered unnecessary to mark the insects individually and they
Figure 3. Histograms showing variations in body length in the Stag Beetle.