THE DRAGON FLY.
Were we to select from among the insects a type of all that is savage,
relentless, and bloodthirsty, the Dragon fly would be our choice. From
the moment of its birth until its death, usually a twelve-month, it
riots in bloodshed and carnage. Living beneath the waters perhaps eleven
months of its life, in the larva and pupa states, it is literally a
walking pitfall for luckless aquatic insects; but when transformed into
a fly, ever on the wing in pursuit of its prey, it throws off all
concealment, and reveals the more unblushingly its rapacious character.
Not only do its horrid visage and ferocious bearing frighten children,
who call it the "Devil's Darning-needle," but it even distresses older
persons, so that its name has become a byword. Could we understand the
language of insects, what tales of horror would be revealed! What
traditions, sagas, fables, and myths must adorn the annals of animal
life regarding this Dragon among insects!
To man, however, aside from its bad name and its repulsive aspect, which
its gay trappings do not conceal, its whole life is beneficent. It is a
scavenger, being like that class ugly and repulsive, and holding
literally, among insects, the lowest rank in society. In the water, it
preys upon young mosquitoes and the larvæ of other noxious insects. It
thus aids in maintaining the balance of life, and cleanses the swamps of
miasmata, thus purifying the air we breathe. During its existence of
three or four weeks above the waters, its whole life is a continued good
to man. It hawks over pools and fields and through gardens, decimating
swarms of mosquitoes, flies, gnats, and other baneful insects. It is a
true Malthus' delight, and, following that sanguinary philosopher, we
may believe that our Dragon fly is an entomological Tamerlane or
Napoleon sent into the world by a kind Providence to prevent too close a
jostling among the myriads of insect life.
We will, then, conquer our repugnance to its ugly looks and savage mien,
and contemplate the hideous monstrosity,--as it is useless to deny that
it combines the graces of the Hunchback of Notre Dame and Dickens'
Quilp, with certain features of its own,--for the good it does in
Nature.
Even among insects, a class replete with forms the very incarnation of
ugliness and the perfection of all that is hideous in nature, our Dragon
fly is most conspicuous. Look at its enormous head, with its beetling
brows, retreating face, and heavy under jaws,--all eyes and teeth,--and
hung so loosely on its short, weak neck, sunk beneath its enormous
hunchback,--for it is wofully round-shouldered,--while its long, thin
legs, shrunken as if from disease, are drawn up beneath its breast, and
what a hobgoblin it is!
Its gleaming wings are, however, beautiful objects. They form a broad
expanse of delicate parchment-like membrane drawn over an intricate
network of veins. Though the body is bulky, it is yet light, and easily
sustained by the wings. The long tail undoubtedly acts as a rudder to
steady its flight.
These insects are almost universally dressed in the gayest colors. The
body is variously banded with rich shades of blue, green, and yellow,
and the wings give off the most beautiful iridescent and metallic
reflections.
During July and August the various species of Libellula and its allies
most abound. The eggs are attached loosely in bunches to the stems of
rushes and other water-plants. In laying them, the Dragon fly, according
to Mr. P. R. Uhler's observations, "alights upon water-plants, and,
pushing the end of her body below the surface of the water, glues a
bunch of eggs to the submerged stem or leaf. Libellula auripennis I have
often seen laying eggs, and I think I was not deceived in my observation
that she dropped a bunch of eggs into the open ditch while balancing
herself just a little way above the surface of the water. I have, also,
seen her settled upon the reeds in brackish water with her abdomen
submerged in part, and there attaching a cluster of eggs. I feel pretty
sure that L. auripennis does not always deposit the whole of her eggs at
one time, as I have seen her attach a cluster of not more than a dozen
small yellow eggs. There must be more than one hundred eggs in one of
the large bunches. The eggs of some of the Agrions are bright
apple-green, but I cannot be sure that I have ever seen them in the very
act of oviposition. They have curious habits of settling upon leaves and
grass growing in the water, and often allow their abdomens to fall below
the surface of the water; sometimes they fly against the surface, but I
never saw what I could assert to be the projecting of the eggs from the
body upon plants or into the water. The English entomologists assert
that the female Agrion goes below the surface to a depth of several
inches to deposit eggs upon the submerged stems of plants." The Agrions,
however, according to Lucaze Duthiers, a French anatomist, make, with
the ovipositor, a little notch in the plant upon which they lay their
eggs.
[Illustration: 127. Under side of head of Diplax, with the labium or
mask fully extended. _x_, _x_', _x_''the three subdivisions of the
labium. _y_, the maxillæ or second pair of jaws.]
These eggs soon hatch, probably during the heat of summer. The larva is
very active in its habits, being provided with six legs, attached to the
thorax, on the back of which are the little wing-pads, or rudimentary
wings. The large head is provided with enormous eyes, while a pair of
simple, minute eyelets (ocelli) are placed near the origin of the small
bristle-like feelers, or antennæ. Seen from beneath, instead of the
formidable array of jaws and accessory organs commonly observed in most
carnivorous larvæ, we see nothing but a broad, smooth mask covering the
lower part of the face; as if from sheer modesty our young Dragon fly
was endeavoring to conceal a gape. But wait a moment. Some unwary insect
comes within striking distance. The battery of jaws is unmasked, and
opens upon the victim. This mask (Fig. 127) is peculiar to the young,
or larva and pupa of the Dragon fly. It is the labium, or under lip
greatly enlarged, and armed at the broad spoon-shaped extremity (Fig.
127, _x_) with two sharp hooks, adapted for seizing and retaining its
prey. At rest, the terminal half is so bent up as to conceal the face,
and thus the creature crawls about, to all appearance, the most innocent
and lamb-like of insects.
[Illustration: 128. Abdominal valves; _a_, side view.]
Not only does the immature Dragon fly walk over the bottom of the pool
or stream it inhabits, but it can also leap for a considerable distance,
and by a most curious contrivance. By a syringe-like apparatus lodged in
the end of the body, it discharges a stream of water for a distance of
two or three inches behind it, thus propelling the insect forwards. This
apparatus combines the functions of locomotion and respiration. There
are, as usual, two breathing pores (stigmata) on each side of the
thorax. But the process of breathing seems to be mostly carried on in
the tail. The tracheæ are here collected in a large mass, sending their
branches into folds of membrane lining the end of the alimentary canal,
and which act like a piston to force out the water. The entrance to the
canal is protected by three to five triangular horny valves (Fig. 128,
9, 10, 128 _a_, side view), which open and shut at will. When open, the
water flows in, bathing the internal gill-like organs, which extract the
air from the water, which is then suddenly expelled by a strong muscular
effort.
[Illustration: 129. Agrion; _b_, False Gill of Larva.]
In the smaller forms, such as Agrion (A. saucium, Fig. 129; Fig. 129
_b_, side view of false gill, showing but one leaf), the respiratory
leaves, called the tracheary, or false-gills, are not enclosed within
the body, but form three broad leaves, permeated by tracheæ, or
air-vessels. They are not true gills, however, as the blood is not
aerated in them. They only absorb air to supply the tracheæ, which
aerate the blood only within the general cavity of the body. These false
gills also act as a rudder to aid the insect in swimming.
It is interesting to watch the Dragon flies through their
transformations, as they can easily be kept in aquaria. Little, almost
nothing, is known regarding their habits, and any one who can spend the
necessary time and patience in rearing them, so as to trace up the
different stages from the larva to the adult fly, and describe and
figure them accurately, will do good service to science.
[Illustration: 130. Pupa of Cordulia.]
Mr. Uhler states that at present we know but little of the young stages
of our species, but the larva and pupa of the Libellulas may be always
known from the Æschnas by the shorter, deeper and more robust form, and
generally by their thick clothing of hair. Figure 130 represents the
pupa of Cordulia lateralis, and figure 131 that of a Dragon fly referred
doubtfully to the genus Didymops. For descriptions and figures of other
forms the reader may turn to Mr. Louis Cabot's essay "On the Immature
State of the Odonata," published by the Museum of Comparative Zoology at
Cambridge.
[Illustration: 131. Pupa of Didymops?]
The pupa scarcely differs from the larva, except in having larger
wing-pads (Fig. 132). It is still active, and as much of a gourmand as
ever. When the insect is about to assume the pupa state, it moults its
skin. The body having outgrown the larva skin, by a strong muscular
effort a rent opens along the back of the thorax, and the insect having
fastened its claws into some object at the bottom of the pool, the pupa
gradually works its way out of the larva-skin. It is now considerably
larger than before. Immediately after this tedious operation, its body
is soft, but the crust soon hardens. This change, with most species,
probably occurs early in summer.
[Illustration: 132. Pupa of Æschna.]
When about to change into the adult fly, the pupa climbs up some plant
near the surface of the water. Again its back yawns wide open, and from
the rent our Dragon fly slowly emerges. For an hour or more, it remains
torpid and listless, with its flabby, soft wings remaining motionless.
The fluids leave the surface, the crust hardens and dries, rich and
varied tints appear, and our Dragon fly rises into its new world of
light and sunshine a gorgeous, but repulsive being. Tennyson thus
describes these changes in "The Two Voices":--
To-day I saw the Dragon fly
Come from the wells where he did lie.
An inner impulse rent the veil
Of his old husk: from head to tail
Came out clear plates of sapphire mail.
He dried his wings; like gauze they grew;
Through crofts and pastures wet with dew
A living flash of light he flew.
Of our more common, typical forms of Dragon flies, we figure a few,
commonly observed during the summer. The three-spotted Dragon fly
(Libellula trimaculata), of which figure 133 represents the male, is so
called from the three dark clouds on the wings of the female. But the
opposite sex differs in having a dark patch at the front edge of the
wings, and a single broad cloud just beyond the middle of the wing.
Libellula quadrimaculata, the four-spotted Dragon fly (Fig. 134), is
seen on the wing in June, flying through dry pine woods far from any
standing water.
[Illustration: 133. Libellula trimaculata, male.]
[Illustration: 134. Libellula quadrimaculata.]
The largest of our Dragon flies are the "Devil's Darning-needles,"
Eschna heros and grandis, seen hawking about our gardens till dusk. They
frequently enter houses, carrying dismay and terror among the children.
The hind-body is long and cylindrical, and gaily colored with bright
green and bluish bands and spots.
[Illustration: 135. Diplax Berenice, male.]
[Illustration: 136. Diplax Berenice, female.]
[Illustration: 137. Larva of Diplax.]
One of our most common Dragon flies is the ruby Dragon fly, Diplax
rubicundula, which is yellowish-red. It is seen everywhere flying over
pools, and also frequents dry sunny woods and glades. Another common
form is Diplax Berenice (Fig. 135 male, Fig. 136 female. The
accompanying cut (137) represents the larva, probably of this species,
according to Mr. Uhler.) It is black, the head blue in front, spotted
with yellow, while the thorax and abdomen are striped with yellow. There
are fewer stripes on the body of the male, which has only four large
yellow spots on each side of the abdomen. Still another pretty species
is Diplax Elisa (Fig. 138). It is black, with the head yellowish and
with greenish-yellow spots on the sides of the thorax and base of the
abdomen. There are three dusky spots on the front edge of each wing, and
a large cloud at the base of the hind pair towards the hind angles of
the wing.
Rather a rare form, and of much smaller stature is the Nannophya bella
(Fig. 138, female). It was first detected in Baltimore, and we
afterwards found it not unfrequently by a pond in Maine. Its abdomen is
unusually short, and the reticulations of the wings are large and
simple. The female is black, while the male is frosted over with a
whitish powder. Many more species of this family are found in this
country, and for descriptions of them we would refer the reader to Dr.
Hagen's "Synopsis of the Neuroptera of North America," published by the
Smithsonian Institution.
[Illustration: 138. Diplax Elisa.]
[Illustration: 139. Nannophya bella.]
[Illustration: 140. May Fly.]
The Libellulidæ, or family of Dragon flies, and the Ephemeridæ, or May
flies (Fig. 140), are the most characteristic of the Neuroptera, or
veiny-winged insects. This group is a most interesting one to the
systematist, as it is composed of so many heterogeneous forms which it
is almost impossible to classify in our rigid and at present necessarily
artificial systems. We divide them into families and sub-families,
genera and sub-genera, species and varieties, but there is an endless
shifting of characters in these groups. The different groups would seem
well limited after studying certain forms, when to the systematist's
sorrow, here comes a creature, perhaps mimicking an ant, or aphis, or
other sort of bug, or even a butterfly, and for which they would be
readily mistaken by the uninitiated. Bibliographers have gone mad over
books that could not be classified. Imagine the despair of an
insect-hunter and entomophile, as he sits down to his box of dried
neuroptera. He seeks for a true neuropter in the white ant before him,
but its very form and habits summon up a swarm of true ants; and then
the little wingless book louse (Atropos, Fig. 141) scampering
irreverently over the musty pages of his Systema Naturæ, reminds him of
that closest friend of man--Pediculus vestimenti. Again, his studies
lead him to that gorgeous inhabitant of the South, the butterfly-like
Ascalaphus, with its resplendent wings, and slender, knobbed antennæ so
much like those of butterflies, and visions of these beautiful insects
fill his mind's eye; or sundry dun-colored caddis flies, modest,
delicate neuroptera, with finely fringed wings and slender feelers,
create doubts as to whether they are not really allies of the clothes
moth, so close is the resemblance.
[Illustration: 141. Death Tick.]
Thus the student is constantly led astray by the wanton freaks Nature
plays, and becomes sceptical as regards the truth of a natural system,
though there is one to be discovered; and at last disgusted with the
stiff and arbitrary systems of our books,--a disgust we confess most
wholesome, if it only leads him into a closer communion with nature. The
sooner one leaves those maternal apron-strings,--books,--and learns to
identify himself with nature, and thus goes out of himself to affiliate
with the spirit of the scene or object before him,--or, in other words,
cultivates habits of the closest observation and most patient
reflection,--be he painter or poet, philosopher or insect-hunter of low
degree, he will gain an intellectual strength and power of interpreting
nature, that is the gift of true genius.
[Illustration: The Ant Lion and adult.]