Insects of this order are without wings, and the name is derived from
two Greek words, [Greek: a], privative, and [Greek: pteron], wing,
indicating the negative character which constitutes this order.[9] It
consists of Fleas and Lice. The Flea (_Pulex_), of which De Geer
formed a separate group, and called _Suctoria_, includes several
species.
[9] It is probable that one day the order Aptera will be
superseded. The absence of wings is not really a character of
great value. De Blainville, Mollard, Pouchet, Van Beneden, and
Gervais, have made several attempts in that direction. The
fleas have been placed among the Diptera, and the lice among
Hemiptera in the "Traité de Zoologie Médicale" of these two
last authors.
The common flea (_Pulex irritans_, Fig. 17) has a body of oval form,
somewhat flattened, covered with a rather hard horny skin of a
brilliant chestnut brown colour. It is the breaking of this hard skin
which produces the little crack which is heard when, after a
successful hunt, one has the happiness to crush one of these parasites
between one's nails.
[Illustration: Fig. 17.--Flea (_Pulex irritans_).]
Its head, small in proportion to the body, is compressed, and carries
two small antennæ, of cylindrical form, composed of four joints, which
the animal shakes continually when in motion, but which it lowers and
rests in front of its head when in a state of repose. The eyes are
simple, large, and round. The beak is composed of an exterior jointed
sheath, having inside it a tube, and carrying underneath two long
sharp lancets, with cutting and saw-like edges. It is with this
instrument that the flea pierces the skin, irritates it, and causes
the blood on which it lives to flow.
This bite, as every one knows, is easily recognised by the presence of
small darkish red spots, surrounded by a circle of a paler colour.
The quantity of blood absorbed by this little creature is enormous,
when compared with its size.
The body of the flea is divided into thirteen segments, of which one
forms the head; three the thorax, which is short, and the remainder
the abdomen.
The limbs are long, strong, and spiny. The tarsus, or foot, has five
joints, and terminates in hooks turned in opposite directions. The two
anterior limbs are separated from the others, and are inserted nearly
under the head; the posterior ones are particularly large and strong.
The jumps which fleas are able to make are really gigantic, and the
strength of these little animals quite herculean, when compared with
the size of their bodies. The reader may be inclined to smile at the
assertion that the flea possesses herculean strength; but let him wait
a little, and he will find that it is no exaggeration.
To give some idea of the strength, the docility, and the goodwill of
the fleas, some wonderful little things have been made, which have
served at the same time to show the astonishing skill of certain
workmen.
In his "Histoire abrégée des Insectes," published in the seventh year
of the French Republic, Geoffroy relates that a certain Mark, an
Englishman, had succeeded, by dint of patience and art, in making a
gold chain the length of a finger, with a padlock and a key to fasten
it, not exceeding a single grain in weight. A flea attached to the
chain pulled it easily. The same learned writer relates a still more
surprising fact. An English workman constructed a carriage and six
horses of ivory. The coachman was on the box, with a dog between his
legs, there were also a postillion, four persons in the carriage, and
two servants behind, and the whole of this was drawn by one flea.
In his "Histoire Naturelle des Insectes Aptères," Baron Walckenaer
relates the following marvellous instance of industry, patience, and
dexterity:--
"I think it is about fifteen years ago, that the whole population of
Paris could see the following wonders exhibited on the Place de la
Bourse for sixty centimes. They were the learned fleas. I have seen
and examined them with entomological eyes, assisted by a glass.
"Thirty fleas went through military exercise, and stood upon their
hind legs, armed with pikes, formed of very small splinters of wood.
"Two fleas were harnessed to and drew a golden carriage with four
wheels and a postillion. A third flea was seated on the coach-box, and
held a splinter of wood for a whip. Two other fleas drew a cannon on
its carriage; this little trinket was admirably finished, not a screw
or a nut was wanting. These and other wonders were performed on
polished glass. The flea-horses were fastened by a gold chain attached
to the thighs of their hind legs, which I was told was never taken
off. They had lived thus for two years and a half, not one having died
during the period. To be fed, they were placed on a man's arm, which
they sucked. When they were unwilling to draw the cannon or the
carriage, the man took a burning coal, and on it being moved about
near them, they were at once roused, and recommenced the
performances."
The learned fleas were the admiration and amazement of Paris, Lyons,
and the chief provincial towns of France, in 1825.
But how, one will ask, was it possible in a large public room to see
this wonderful sight? And it is necessary that this should be
explained. The spectators were seated in front of a curtain, provided
with magnifying glasses, through which they looked, as they would at a
diorama of landscapes or buildings.
But let us return to the natural history of our insect. The female
flea lays from eight to twelve eggs, which are of oval shape, smooth,
viscous, and white.
Contrary to what one might think, _à priori_, the flea does not fix
its eggs to the skin of its victims. She lets them drop on the ground,
between the boards of floors, or old furniture, and among dirty linen
and rubbish.
M. Defrance has remarked that there are always found mixed with the
eggs a certain number of grains of a brilliant black colour, which are
simply dried blood. This is a provision which the foreseeing mother
has prepared at our expense to nourish her young offspring.
In four or five days in summer, and in eleven days in winter, one may
see coming out of these eggs small, elongated larvæ, of cylindrical
form, covered with hair, and divided into three parts, the last
provided with two small hooks. The head is scaly above, has two small
antennæ, and is without eyes. These larvæ are without limbs, but they
can twist about, roll themselves over and over, and even advance
pretty fast by raising their heads. Though at first white, they become
afterwards of a reddish colour.
About a fortnight after they are hatched they cease to eat, and are
immovable, as if about to die. They then commence to make a small,
whitish, silky cocoon, in which they are transformed into pupæ. In
another fortnight these pupæ become perfect insects.
A most remarkable trait, and unique among insects, has been observed
in the flea. The mother disgorges into the mouths of the larvæ the
blood with which she is filled.
The flea is most abundant in Europe and the North of Africa. Certain
circumstances particularly favour its multiplication; being most
abundant in dirty houses, in barracks, and in camps; in deserted
buildings, in ruins, and in places frequented by people of uncleanly
habits.
Other kinds of fleas live on animals, as, for example, the cat flea,
the dog flea, and those of the pigeon and poultry.
We shall say a few words about a peculiar species which abounds in all
the hot parts of America, but principally in the Brazils and the
neighbouring countries. This formidable species is the Chigo (_Pulex
penetrans_).
The chigo, called also the tick, is smaller than the common flea. It
is flat, brown with a white spot on the back, and is armed with a
strong pointed stiff beak, provided with three lancets. It is with
this instrument that the female attacks man with the intention of
lodging in his skin and bringing forth her young there.
The chigo attacks chiefly the feet. It slips in between the flesh and
the nails, or gets under the skin of the heel. Notwithstanding the
length of the animal's beak, introducing itself beneath the skin does
not at first cause any pain; but after a few days one is made aware of
its presence by an itching, which, though at first slight, gradually
increases, and ends by becoming unbearable.
The chigo, when under the skin, betrays itself by a bump outside. Its
body has now become as large as a pea; in the attacked skin a large
brown bag containing matter is formed. In this bag are collected the
eggs, which issue from an orifice in the posterior extremity, and are
not hatched in the wound itself, as was long thought to be the case.
The chigoes are an object of terror to the Brazilian negroes. These
formidable parasites sometimes attack the whole of the foot, which
they devour, and thus bring on mortification; many negroes losing the
bones of some of their toes by the ravages of these dangerous
creatures. To guard against their attacks, they wear thick shoes, and
examine their feet carefully every day. The plan usually followed in
the Brazils to prevent the chigoes from injuring the feet, is to
employ children, who, by their sharpness of sight, can easily perceive
the red spot on the skin where the chigo has entered. These children
are in the habit of extracting the insect from the wound by means of a
needle. But this is not without risk; as, if any portion of the insect
remains in the wound, a dangerous inflammation may ensue. For this
reason, operators who are renowned for their skill are much sought
after, flattered, and rewarded by the poor negroes of the plantations.
[Illustration: Fig. 18.--Louse (_Pediculus capitis_) magnified.]
The Head Louse (_Pediculus capitis_, Fig. 18) is an insect with a flat
body, slightly transparent, and of greyish colour, spotted with black
on the spiracles, soft in the middle, and rather hard at the sides.
The head, which is oval, is furnished with two thread-like antennæ,
composed of five joints, which are constantly in motion while the
creature is walking; it is also furnished with two simple, round,
black eyes; and lastly, with a mouth. In the front of the head is a
short, conical, fleshy nipple. This nipple contains a sucker, or
rostrum, which the animal can put out when it likes, and which, when
extended, represents a tubular body, terminating in six little pointed
hooks, bent back, and serving to retain the instrument in the skin.
This organ is surmounted by four fine hairs, fixed to one another, and
seated in its interior. It is by means of this complicated apparatus
that the louse pricks and sucks the skin of the head. The thorax is
nearly square, and divided into three parts by deep incisions. The
abdomen, strongly lobed at the sides, is composed of eight rings, and
is provided with sixteen spiracles. The limbs consist of a trochanter,
a thigh, a shank, and a tarsus of a single joint, and are very thick.
A strong nail, which folds back on an indented projection, thus
forming a pincer, terminates the tarsus. It is with this pincer that
the louse fastens itself to the hair.
Lice are oviparous. Their eggs, which remain sticking to the hair, are
long and white, and are commonly called "nits." The young are hatched
in the course of five or six days; and in eighteen days are able to
reproduce their kind. Leuwenhoek calculated that in two months two
female lice could produce ten thousand! Other naturalists have
asserted that the second generation of a single individual can amount
to two thousand five hundred, and the third, to a hundred and
twenty-five thousand! Happily for the victims of these disgusting
parasites, their reproduction is not generally to this prodigious
extent.
Many means are employed to kill lice. Lotions of the smaller centaury
or of stavesacre, and pomatum mixed with mercurial ointment, are very
efficacious. But the surest and easiest remedy is to put plenty of oil
on the head. The oil kills the lice by obstructing their tracheæ, and
thus stopping respiration.
There are other kinds of lice, but we will only mention the louse
which infests beggars and people of unclean habits, _Pediculus humanus
corporis_, producing the complaint called phthiriasis. In the victims
of this disease these parasites increase with fearful rapidity. This
dreadful disorder is often mentioned by the ancients. King Antiochus,
the philosopher Pherecydes of Scyros, the contemporary and friend of
Thales, the dictator Sylla, Agrippa, and Valerius Maximus, are said to
have been attacked by phthiriasis, and even to have died of it. Amatus
Lusitanus, a Portuguese doctor of the sixteenth century, relates that
lice increased so quickly and to such an extent on a rich nobleman
attacked with phthiriasis, that the whole duty of two of his servants
consisted in carrying away, and throwing into the sea, whole
basketfuls of the vermin, which were continually escaping from the
person of their noble master.
Little is known at the present day of the details of this complaint,
though it is observed frequently enough in some parts of the south of
Europe, where the dirty and miserable inhabitants are a prey to
poverty and uncleanliness--two misfortunes which often go together. In
Gallicia, in Poland, in the Asturias, and in Spain, we may find many
victims of phthiriasis.
Lice increase with such rapidity on persons thus attacked, that it is
common to attribute their appearance to spontaneous generation alone.
But the prodigious rapidity of reproduction in these insects
sufficiently explains their increase, especially when it is admitted
that it is possible for the female louse to reproduce young without
the agency of the male.
The Thysanura or "Skip Tail" tribe are small insects, which are better
known on account of the beauty of their microscopic body scales than
for any interesting habits or instincts. They do not undergo
metamorphosis.
The Fish Scale or _Lepisma saccharina_, and the Skip Tail or _Podura
plumbea_ belong to the Thysanura.