STUBBS : A BLUE EGG OF THE LAPWING. 105
Page 101.
M. Unionicola crassipes. Mull.
Ventral surface. ♀ X —37
N. Three last segments of palpi.
O. Genital area, ♂. 140
P. Arrhenurus caudatus, de Geer.
Dorsal surface ♂ X —37
Q. Palpi of ♂ X —100
R. Dorsal surface ♀ X —35
S. Genital area. ♀ X —38
T. Arrhenurus maculator. Mull.
Dorsal surface. ♂ X —35
U. Genital area. ♀ X —40
V. Atractides anomalus. Koch.
Ventral surface. ♀ X —55
W. Arrhenurus alabator. Mull.
Petiole of ♂ X —87
ON A BLUE EGG OF THE LAPWING.
By FREDK. J. STUBBS.
[Read 30th October 1915.]
THE egg now exhibited was picked up by Mr. Gilbert
Debenham, on 1st April 1915, between Theydon Bois
and Abridge. It was not near a nest, and had obviously been
sucked by a crow. In districts where Lapwings are numerous,
I have met with similar eggs on two occasions, and have heard
of a few others, all found empty.
The ground-colour of the specimen in question may well be
likened to that of a Starling's egg, and the dark markings are
smaller than is usual in normal specimens. Such eggs are, of
course, very conspicuous, and cannot well escape the eyes of
nest-robbing birds.
The subject is an interesting one. Very little has been done
in the study of the colours of eggs since Dr. Sorby's researches
in 1875 (P.Z.S., 1875, pp. 351-365). By the aid of spectrum-
analysis, he proved the existence of seven colouring matters,
of which two only need be mentioned here. One is the substance
which he called "oorhodeine," found in brown and red eggs:
the other is "oocyan," a constituent of blue shells. Both appear
to be present in greenish-brown eggs, such as those of the Nightin-
gale, Pheasant, Lapwing, etc. Sometimes, the oocyan is absent;
H