The Mediterranean 
& flDontbl\> 3ournal of IRatural Science. 
Yol. II., No. 13. MALTA, JUNE 1st. 1892. 
CONTENTS. 
— »» — Pag. 
1 A Year’s insect hunting at Gibraltar— J. J, Walker, 
R.N., F.E.S. - , 187 
2 Why do we teach Geology. 189 
3 The Sulphur Mines of Sicily. 19U 
4 The Relationship of the structure of Rocks to the 
conditions of their Formation— H. J. Johnston 
Lavis, M.D., etc. 190 
5 Subterranean Water in the Sahara. 194 
6 The Malta Potato Disease— J. H. C. 194 
7 On the .Meadow of Nysa in Asia Minor — Capt. R. 
Moore, R.N. 195 
8 Vanishing Forms. 197 
9 Algerian Oases. 197 
10 Prehistoric Man in the Mediterranean. 198 
11 Fossil Birds in Corsica & Sardinia. 199 
12 Notes and News:— Discovery of Salt in Egypt — 
Humanity's future on Earth— Irrigation in Egypt 
—Imitative Forms in Rocks— An Uncanny cu- 
stomer— Malta's Spring Visitors— Climate of the 
Sahara — Earthquakes and Pla.nt Growth — A 
novel Industry, etc. etc. 200 
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A year’s insect-hunting at Gibraltar. 
BY JAMES J. WALKER, R.N., F.E.S. 
The insect fauna of the south of Spain has been 
investigated by such well-known Entomologists as 
Rambur, Graslin, Rosenhauer, Diek, &c.; but, as 
far as I have been able to ascertain, nothing has 
been published respecting that of our British 
possession at Gibraltar and the immediate neigh- 
bourhood, except some notes on the butterflies in 
the “Entomologist” (Nos. 257 and 247, Nov. and 
Dec., 1884). As I have had ample opportunities 
of collecting in this very interesting locality since 
my appointment to H. M. gunboat “Grappler” 
stationed here, I venture to put my experiences on 
record, as a contribution to the knowledge of the 
entomology of this extreme southern corner of the 
European continent, prefacing them with a brief 
account of the chief physical and botanical fea- 
tures of the district. 
The Rock of Gibraltar is a huge isolated mass 
of hard greyish-white limestone of Jurassic age, 
about 2| miles in extreme length, with a varying 
width, at the sea-level, of from 440 to 1300 yards. 
A level, sandy isthmus, scarcely ten feet above 
high-water mark in any part, connects it with the 
Spanish mainland, and from this the northern 
face of the Rock rises in one magnificent vertical 
precipice to a height of over 1200 feet. Thence, 
for rather more than a mile, the crest of the Rock 
is a narrow knife-edge ridge, running nearly north 
and southland varying in height from 1356 feet 
near the north end, to only 660 feet at less than a 
quarter of a mile south of this point. It again 
rises to 1275 feet at the Signal Station, near the 
middle of the ridge, and attains its greatest eleva- 
tion (1386 feet) between this spot and “O’Hara’s 
Tower,” which surmounts its southern extremity. 
From here the Rock descends in a series of grand 
precipices to the “Windmill Hill Flats,” some 400 
feet above the sea, and again sinks abruptly to 
Europa Point, which presents a cliff of about 50 
