of Forficula auricularia in the Scilly Islands. 329 
The variation between different years is not wide enough to 
discredit the conclusion that in some of the Scilly Islands the 
percentage of males is habitually low, while in others it 1s above 
the average. 
The proportions of the sexes observed in Scilly have very little 
relation to the mutual positions of the islands. Comment on these 
points may be deferred till after a brief mention of the situations 
in which earwigs were found most abundantly. The Scilly Islands 
are granite with much blown sand, which is especially abundant 
on Tresco. There is an outcrop of altered Killas on White Island, 
N.W. of St Martin’s, and on the latter a patch of gravel which is 
possibly of Eocene date. Glacial deposits occur on the larger 
islands, especially in the north of the group. There is a little 
alluvium on St Mary’s*. 
The whole group of islands is included in a parallelogram of 
6 x 8 miles, and St Mary’s, the largest island, does not exceed two 
miles in its longest diameter. 
Taking the islands in an order which is roughly N.E. to 8.W., 
the most northerly is 
Round Island.—This dome-like mass of granite is 135 ft. high 
and inaccessible save for the Trinity House steps cut on the 
S. side. Its only inhabitants are the three light-keepers. The 
commonest plants are Armeria maritima, Cochlearia officinalis 
and Mesembryanthemum edule. There is no turf. The light- 
keepers throw their potato peelings and other kitchen refuse down 
the N.E. slope, and this midden swarms with earwigs under 
detached stones and in old meat tins. They are not numerous 
on the rest of the islet and there is no doubt that their food is 
mainly the kitchen refuse. They are mostly large-bodied and the 
high male is exceedingly common. The presence of man has 
apparently favoured their increase in this spot. (In the above and 
other references to the average size of body in adults, the state- 
ment covers both sexes) 
St Helen’s—This island is also dome-like, but is about twice 
the size of Round Island and has much turf with scattered stones, 
while the rocky shore of its 8. side has a fringe of bracken fern 
which grows high and thickly. On this fringe is the ruined 
“Pest House,” an old quarantine hospital. ‘There are now no 
inhabitants. Prolonged search all round the island discovered 
earwigs only in this neighbourhood. They were not numerous 
and nearly all were found under fallen slates and masonry in and 
about the Pest House. These earwigs were mostly fairly large and 
high males were common. 
Tean.—A low irregular island uninhabited save by grazing 
cattle. It is nearly all turf-covered and has a fringe of blown 
* G. Barrow, Geological Survey Memoir; Isles of Scilly, 1906. 
