BIOLOGICAL NOTES ON DRAGON-FLIES. 297
remains stationary for a time whilst the skin dries. A split then
appears on the back of the thorax, and through this split the
thorax is first pushed; the head is then drawn out, followed
by the wings and legs. The insect then rests for a period.
In the Zygoptera the head is retained in a forward position, but
in the Anisoptera the head and thorax drop backward ; in each
the abdomen is retained within the naiad skin. After resting,
the dragonfly grasps the support with its feet and crawls up,
drawing the abdomen out of the naiad-skin. The wings then
commence to expand from their base outward, during which
expansion the body is pulsating rapidly.
The following is a list of those dragonflies that I have
taken in the neighbourhood of Epping Forest during the last
fifteen years :—
ANISOPTERA. ZYGOPTERA.
Aeshnidae. Calopterygidae.
Brachytron pratense, Mull. Calopteryx virgo, Linn.
Aeschna grandis, Linn. Calopteryx splendens, Harris.
Aeschna cyanea, Mull. Lestidae.
Anax imperator, Leach. Lestes sponsa, Hans.
Libellulidae. Arionidae.
Cordulia aenea, Linn. Platycnemis pennipes, Pall.
Libellula quadrimaculata, Linn. Ischnura elegans, Lind.
Libellula depressa, Linn. Agrion pulchellum, Lind.
Sympetrum striolatum, Charp. Agrion puella, Linn.
Sympetrum sanguineum, Mull. Erythromma naias, Hans.
Sympetrum scoticum, Don. Pyrrhosoma nymphula, Sulz.
Enallagma cyathigerum, Charp.
In addition Sympetrum flaveolum, L., has also been recorded
from the Forest.
Rhaxella Chert at Great Parndon.—On 26th August, 1929, my
wife found a cuboidal block of Rhaxella Chert, measuring 61/2in. x 63/8in.
x 31/2 in., in situ in Mid-Glacial Gravel at Great Parndon, at just below
200 ft. O.D.
Percy Thompson.