BIOLOGICAL NOTES ON DRAGON-FLIES. 295
female whilst she is ovipositing. In all the Zygopterid dragonflies
that I have seen ovipositing the male was in attendance, but I
have seen Aeschna grandis and A. cyanea ovipositing without the
attendant male.
The anal appendages differ in the two suborders ; in the
Anisoptera the male has two superior appendages and below
these a medial inferior appendage, which is placed just above
the anus. In the female the inferior appendage is absent. The
function of the male appendages is to clasp the female, the
superior appendages grasping the back of the head of the female
whilst the inferior presses down upon the occiput.
In the Zygoptera there are two pairs of processes, the superior
being as in the Anisoptera but the inferior appendages are two
in number and are below the anus, one on each side. In these
the appendages act like forceps and grip not the head, but the
pronotum of the female, the pronotum being modified to pair
with the claspers of the male.
The ova of dragonflies are of two forms; those produced
by the females with an ovipositor are cylindrical, while those
without an ovipositor produce spherical eggs ; both forms have
a short pedicel. The larva of a dragonfly is generally called a
naiad.
Comstock, in his Introduction to Entomology, proposes to
restrict the terms "larva" and "pupa" to those insects which
have a complete metamorphosis, i.e., Butterflies, Moths, Beetles,
etc., "nymph" to those with a gradual metamorphosis, i.e.,
Grasshoppers, Earwigs, Bugs, "naiad" to those with an in-
complete metamorphosis.
The creature that emerges from the egg is very different from
the naiad, and is generally spoken of as a "pronymph" ; this
should be called a "pronaiad." The hatching of the pronaiad
has been described by both Balfour Browne and Tillyard.
They inform us that the embryo can be seen through the egg-
shell, the head fitting close up to the cap ; a cephalic heart appears
and this seems to pump fluid up to the front of the head, which
forces the cap upwards and backwards, then the pronaiad gently
flows out of the shell. The labium and legs are all held down close
to the body by an envelope of fine structureless chitin and are
incapable of functioning. The naiad frees itself from this
covering by splitting it along the back of the head and thorax,