are stout caterpillars, 1⅕ to 2 inches long, with five pairs of
pro-legs, and shining transparent external skin. They remain in the
ground during the day, feeding above ground at night, and also in the
daytime when the sky is much overcast. When touched they bend themselves
into the form of a C. There are in Britain several species of surface
caterpillars which have these habits, but I will only describe here, to
begin with, the commonest kind:—
[Illustration:
FIG. 99.—The Common Dart or Turnip Moth (_Agrotis segetum_) with
Caterpillar.
]
The =Common Dart= or =Turnip Moth= (_Agrotis segetum_ or _A.
clavis_).—_Moth_ (Fig. 99): Length almost ⅘ of an inch. Span of wing
about 1⅘ inch. Fore wings small, ash-grey or brownish, with many dark
patches and similar markings. Hind wings in the male, bright grey to
snowy white; in the female, brownish grey. _Caterpillar_ (Fig. 99): Up
to two inches, earthy grey, occasionally somewhat greenish. Head and
prothorax darker. The time taken by the caterpillars to complete their
development differs according to the plants attacked, and it is
therefore easy to understand why the moths should be seen flying about
from the first half of May right on into the autumn, without having
recourse to the improbable hypothesis of two successive generations. The
eggs are consequently laid at very different times, and are always
deposited singly in the soil in the neighbourhood of plant roots, or
else in the low-lying leaves and stems of various herbs. The
caterpillars hatched from these are destructive earlier or later,
according to the time of egg-laying. Most specimens are half grown in
winter; these continue their destructive work the following spring. In
autumn they attack the roots of winter grain (rye and wheat), rape, and
species of cabbage; they also bore readily into turnips and potatoes. In
spring, after the winter rest, they continue to attack the roots of
winter grain, winter rape, etc., or fleshy underground parts (turnips,
potatoes) developed in the interim, or the roots of summer plants
(summer grain, buckwheat, summer rape, vegetables, etc.). On clear days
the caterpillars always remain hidden in the soil; and those which have
bored into juicy underground parts of plants (turnips, carrots), do not
leave their abode during the day, but the others, both during the night
and on cloudy days, come above ground to attack the leaves and stems of
young plants. In exceptional cases the caterpillar is mature by the
beginning of winter, in which case it hybernates in the soil as a brown
pupa. The moths escaping from such pupæ naturally appear earlier than
others. As a rule, the caterpillars do most damage to the winter crop in
autumn, wandering about a great deal; in many cases they gnaw through
the main root, thus quickly killing the plant attacked, from which they
proceed to another. _Remedies_: When the caterpillars have done much
damage in late summer, it is recommended to leave the field alone till
October, then to plough it up and sow the winter grain. By putting off
the seed-time in this way, the caterpillars will have lost their
activity when the corn germinates, and the winter crop will thus escape
them. Besides this, the preceding ploughing will bring many caterpillars
to the surface, where they will become the prey of birds, or, if not,
can be collected. Warm soils, especially those manured with horse dung,
are most infested by the caterpillars; and the use of warm kinds of
manure should, therefore, be avoided in regions which have much to fear
from these insects. Where everything has been destroyed, a thorough
ploughing is desirable. Swine may also be driven in during autumn, and
will grub up and devour the caterpillars. In this case, sowing will take
place the following spring.
Other _Surface Caterpillars_, which have pretty much the same habits as
the preceding, are those of the =Heart and Dart Moth= (_Agrotis
exclamationis_), the =Wheat Moth= (_A. tritici_), and the =Thick-bodied
Surface Caterpillar= (_A. ravida_ or _A. crassa_).
The =Cabbage Moth= (_Mamestra brassicæ_).
_Moth_ (Fig. 100); about ¹¹⁄₁₂ of an inch long, span of wing 1⅗ inch.
Fore wings shining brown, with yellowish and black marbling; each patch
having a dark outline; a yellowish zigzag line on the outer margin. Hind
wings shining yellowish-grey brown. A strongly developed crest in the
middle line of the thorax. _Caterpillar_ (Fig. 100): 1⅗ inches,
cylindrical. Bright or dark green, brownish green, or greenish brown. On
the back a dark longitudinal stripe, divided into two halves by a narrow
white longitudinal line. A whitish line running along each side; between
this and the dorsal line a dark transverse streak on each segment. The
brown pupa (Fig. 100) remains in the soil during the winter, and is not
invested in a cocoon. The moth appears in May; during the day it rests
on windows, in barns, etc. The greenish yellow eggs are laid separately
on the leaves of cabbages (sometimes also on lettuces and turnips). The
caterpillars, which appear in fourteen days, creep about actively
between the leaves. Within a month they are full-grown, and become pupæ
in the soil. At the end of July and in August the summer generation of
moths appears. From the eggs laid by these are hatched a second
generation of caterpillars, which are always much more numerous than
those of the first. From August to October they are found in all kinds
of cabbage, especially compactly headed kinds and cauliflower. At first
they eat holes in the leaves, leaving, however, the chief veins and
usually the edges. Later on they eat right on into the heart of the
cabbage. They fill their burrows with excrement, and the attacked plants
begin to rot internally. The full-grown caterpillars creep out and
become pupa in the soil. _Remedy_: Collecting the caterpillars while
they are still on the outer leaves.
[Illustration:
FIG. 100.—The Cabbage Moth (_Mamestra brassicæ_), with caterpillar and
pupa.
]
The =Vegetable= or =Lettuce Moth= (_Mamestra oleracea_).
_Moth_: ⅗ of an inch long; span of wings about 1⅖ of an inch. Fore wings
dark rusty brown, darker on the nerves, dusted with white. Hind wings
reddish white. Head and thorax like the fore wings; abdomen like the
hind wings. _Caterpillar_: Up to 1⅗ inch; dirty greenish grey, or olive
green, irregularly bestrewn with dirty white dots. The caterpillars feed
on cabbages, lettuce, asparagus, and other vegetables. Those of the
first generation (June and July) hollow out lettuce stalks before the
head begins to be formed; those of the second generation (August and
September) feed on cabbage or asparagus leaves. The first generation of
moths appear in May, the second in the first half of August.
The =Pea Moth= (_Mamestra pisi_).
_Moth_: About ⅖ of an inch long; span of wings about 1⅖ of an inch. Fore
wings bright reddish brown with bluish-grey markings, and a yellowish
longitudinal streak. Hind wings reddish grey. _Caterpillar_: 1⅘ of an
inch; cylindrical; slender. Back dark greenish or brown red; closely and
tolerably regularly veined with dark lines, and with two sulphur yellow
longitudinal streaks on the back and one on each side. Head, belly, and
feet flesh red. If the caterpillar is touched it moves the front part of
its body about here and there, and then lets itself fall down. The moths
appear in May and June; the caterpillars are found from July to
September on peas, vetches, beans, clover, lupins, sorrel, orach, heath,
willow, birch, and yet other plants. Seldom very destructive.
The =Grass-root Moth= (_Hadena monoglypha_, or _H. polyodon_).
_Moth_: About ⅝ of an inch long; span of wing 1⅘ inches. Fore wings
longish; yellow brown blended with dark brown and white; the tips are
coloured most brightly. Three black rays on the fore wing; hind wings
brown grey. _Caterpillar_: About 1⅗ inches long, ⅓ of an inch broad,
with sixteen feet. Grey or reddish white, more or less shining. Head,
prothorax, the last body segment and warts black. At the end of July and
during August the female lays her eggs separately on the bases of grass
haulms and leaves. The caterpillars creep out at the end of August, and,
especially after their hybernation (in April and May), attack meadow
grasses, biting through the leaves and haulms at their bases,
immediately above the surface of the ground, and devouring, as it were,
passages through the grass. The reddish brown pupæ rest in the soil.
The =Couch-grass Moth= (_Hadena basilinea_).
_Moth_: Nearly ⅘ of an inch long; span of wings 1⅗ inches. Head and back
rust-coloured or reddish grey, in the male with a large tuft of hairs.
Fore wings coloured like the back, with two transverse lines in the
middle, and brighter and darker marks as well. Hind wings bright brown,
with a faint golden sheen, and with a yellowish fringe. _Caterpillar_:
1⅕ to 1⅖ inches long, with sixteen feet, bluish grey, somewhat brownish,
with dirty white longitudinal lines; greenish belly, and large bright
brown head. The moth lays the eggs in little heaps on the stems and
leaves of grass plants. The damage which the caterpillars effect among
meadow grasses is inconsiderable; but they sometimes appear in
considerable numbers on grain-plants, and are then very destructive. The
insects are chiefly found on dry high-lying land, which is consequently
most liable to the attacks of their larvæ. After hybernation they feed
on grass or the leaves and stems of young grain-plants, and change in
the soil into stout, smooth, yellowish-brown pupæ, devoid of cocoon.
_Remedy_: In case the caterpillars have got into the crop, threshing
should take place as soon as possible, or, after hybernating, they will
continue to devour the grain in the barns.
The =Wheat-haulm Moth= (_Luperina didyma_).
_Moth_: Span of wing 1⅕ inches. Individual specimens differ very much
from one another: brownish, greyish yellow to ochre yellow, with various
dark and light markings. _Caterpillar_: With sixteen legs, and over an
inch long in full-grown specimens (May); thin, spindle-shaped; stiff;
bright shining green, with two broad dark red lines on the back. The
caterpillars live in the stalks of wheat plants, and other gramineous
forms, hollowing them out; they hybernate when tolerably young. In
spring they continue to hollow out the wheat plants, going from one
stalk to another. The plants attacked quickly have their leaves turned
to a rusty colour, and they sicken or even die.
The =Grass Moth= (_Charæas graminis_).
_Moth_: Length ⅗ of an inch; span of wings about 1⅓ inches. Antennæ of
the male comb-like. Fore wings short, of a brownish-red, olive brown, or
dirty olive-green ground colour, with three whitish patches, and darker
markings. Hind wings yellowish grey, brighter at the roots.
_Caterpillar_: With sixteen legs; 1⅘ inches long; bronze grey, back more
of a bronze brown, with three narrow bright longitudinal streaks. Head
ochre yellow. The moth lays her some two hundred eggs during July, in
little heaps at the bases of the grass haulms and leaves. The
caterpillars hide during the day, and feed at night. They are very
injurious even in the autumn, but become insatiable the following
spring, always devouring the lowest parts of the haulms and leaves, so
that the upper parts die off. They wander in large companies from one
field to another. In June they become pupæ of a shining reddish brown
below the surface of the soil or under sods. _Enemies_: swine, moles,
shrews, rooks, wagtails, ducks, fowls. _Remedy_: Driving in swine, where
this is practicable.
[Illustration:
FIG. 101.—The Grass Moth (_Charæas graminis_) and its caterpillar.
]
The =Darnel Moth= (_Neuronia popularis_).
_Moth_: Length rather less than ⅘ of an inch; span of wings nearly 1⅗
inches. Much variegated, beautiful. Fore legs reddish brown, with
peach-coloured glow; all the nerves and several markings yellowish
white, and dark markings as well. Hind wings yellowish, and abdomen
white. Head and thorax brown, mixed with yellowish white. _Caterpillar_:
Over two inches long, and about one-third of an inch thick; 16-legged;
tapers at both ends. Has an oily lustre. Dorsal side of a bronze brown,
sharply marked off by a yellowish line from the bright brownish grey
ventral side, and traversed by three longitudinal bright brown lines,
which in young specimens are almost white. Habits pretty much like those
of the preceding species.
The =Silver Y Moth= (_Plusia gamma_).
[Illustration:
FIG. 102.—The Silver Y Moth (_Plusia gamma_), with caterpillar and
pupa.
]
_Moth_: About ⅝ of an inch long; span of wings 1¾ inches. Dark grey,
mixed with a reddish tint, and darkly marbled. About the middle of the
fore wing there is a very obvious gamma (γ), or Y-shaped mark. Hind
wings bright brown at the root, darker at the margins, with a whitish
fringe. A crest of hairs on the dorsal side of the thorax.
_Caterpillar_: 12-legged. It bends its body like a looper (Fig. 102).
Length 1 to 1⅕ inches. Ground colour green; but there may be variations
in this from a dirty green to a brownish colour. Six fine longitudinal
lines on the back, and a yellowish line above the legs. The caterpillar
is almost naked, only possessing a few small, isolated bristle-like
hairs. _Habits_: At least two generations, and sometimes as many as five
in two years. The Silver Y Moth generally hybernates as a half-grown
caterpillar, but sometimes also in the pupa, or moth state. The
caterpillars may therefore be met with the whole year; but they are
usually most abundant from the end of June to the middle of August, and,
under favourable conditions, may become an agricultural pest. They
devour the leaves of almost all wild and cultivated plants (except
grasses, corn, and trees), and are especially fond of leguminous plants
(peas, vetches, clover), flax, beet, rape, cabbage, and buckwheat. The
moths mostly appear in May, but also in July, and later on in the
summer, especially on clear days. The female lays her numerous bright
green eggs, some four hundred in number, separately, on the leaves of
the above-named plants. The caterpillars are not always easy to see,
owing to their greenish colour; under favourable conditions they may
pass through the whole of their development up to the moth stage in from
six to seven weeks. In some years they appear in such large numbers,
that almost all the cultivated plants found in the fields of an infested
region are utterly spoilt by them, excepting the corn. _Natural
enemies_: Starlings, all sharp-beaked singing birds haunting fields;
sparrows; ground beetles, rove beetles, and the larvæ of these families;
several ichneumon flies, parasitic fungi. _Remedies_: Driving in
poultry, where practicable. Collecting, _e.g._ by means of a machine
invented by L. Dehoff, of Gutenberg, near Halle. “Several troughs with
steep inner walls are fastened together by laths, at distances equal to
those between adjacent furrows, and besoms are fixed to the laths. These
troughs are drawn along like sledges by a horse walking in the furrows,
and the caterpillars are swept by the besoms into the troughs, from
which they are collected in sacks at the ends of the furrows. With this
cheap machine about twelve acres per day can be cleared” (Taschenberg).
Family: =Pyralidæ= (_Snout Moths_).
Small moths with thread-like antennæ, comb-like in the males of a few
species, with tolerably large eyes, and very large labial palps often
stretched out in front like a beak (Fig. 103). Fore wings of an
elongated triangular shape. Wing booklets. Legs tolerably long.
Caterpillars slightly hairy, with four or five pairs of pro-legs.
The =Rye Snout Moth= (_Pyralis secalis_).
_Moth_: ⅗ of an inch long, span of wings 1⅕ inches. Wings elongated,
whitish grey, with an A-shaped patch on the fore wings. _Caterpillar_:
Rather more than ⅖ of an inch long; green, streaked with brown,
16-legged, with a brown head, and tapering at both ends. _Habits_: The
caterpillar lives during June in the rye haulms, hollowing them out. As
a result of this, the ears remain hidden between the leaves and
leaf-sheaths, and it often happens that only the tips of the awns appear
externally. No grain is formed; the ears first become white and dry, and
then fall off.
The =Hop Snout Moth= (_Hypena rostralis_).
[Illustration:
FIG. 103.—The Hop Snout Moth (_Hypena rostralis_).
]
_Moth_ (Fig. 103): Length rather less than ⅖ of an inch; span of wings
1⅕ inches, or more. Fore wings usually brownish, somewhat scalloped on
the fringed outer margins; a zigzag black line near the base; in the
middle, near the front edge, a patch bordered with white, and behind
this a dark longitudinal streak. Hind wings dull grey, with a silky
sheen. _Caterpillar_: At most one inch long, 14-legged, very slender,
green, with a dark middle line and two white side lines. Very active;
wriggles about on the ground like an eel. _Habits_: The moth is on the
wing at the beginning of August, the second generation in August; the
latter hybernates in outhouses, barns, summer-houses, etc. The eggs are
laid on wild and cultivated hops, also on stinging nettles. The
caterpillars are found on the hop plants, especially in June; they
sometimes entirely devour the leaves, with the exception of the nerves.
In July they become pupæ, either between the leaves or on the soil, and
are invested in a grey cocoon. The moths appear at the beginning of
August, and give rise to a second generation of caterpillars, from
which, after the pupa stage, the moths which live through the winter are
developed.
The =Cabbage Snout Moth= (_Botys forficalis_).
_Moth_: Length about half an inch. Span of wings rather over one inch.
Fore wings sharply bent in front before their sharp tips; rusty yellow,
somewhat darker on the nerves, with rusty brown transverse streaks from
the outermost corners to the middle of the hinder margin, and with other
reddish brown markings. Hind wings and body shining straw yellow.
_Caterpillar_: ⅘ inch long, 16-legged, tapering in front and behind.
Yellowish green, with indistinct longitudinal lines and bright brown
head. A few small yellowish-green hairs. _Habits_: The first generation
appear in small numbers in May. The caterpillars hatched out from the
eggs of these live (May and June) on the leaves of cabbages and wild
cruciferous plants. They always shelter themselves between the leaves,
and spin a few thin threads across the entrances to their abodes. The
caterpillars burrow horizontally in the earth, and there become pupæ
invested in cocoons. The moths of the second generation appear in
August; in autumn the caterpillars hatched from their eggs damage
cabbages, sometimes to a large extent. In October they burrow into the
soil, where they hybernate. _Remedy_: Deep digging or ploughing after
the crop, by which the larvæ invested in webs are buried deeply, and
consequently for the most part killed.
The =Mother-of-pearl Moth= (_Botys margaritalis_ = _B. extimalis_).
_Moth_ (Fig. 104): Length nearly ⅖ inch; span of wing over 1⅕ inches.
Fore wings bright sulphur yellow, with large rust-coloured patches, and
two rusty yellow transverse lines. Hind wings shining straw yellow; all
four wings with a mother-of-pearl sheen. _Caterpillar_ (Fig. 104): ⅘
inch, 16-legged, yellowish, head and neck-shield black. Body with a
broad, grey, longitudinal streak on each side. Four longitudinal rows of
dark brown warts. _Habits_: The moth is on the wing in June and July,
and lays the longish ovoid eggs on cruciferous plants (rape, radish,
several wild forms). The caterpillar lives concealed in a white web, and
gnaws holes in the pods, into which it inserts the forepart of its body
for the purpose of devouring the still green seeds. The attacked pods,
owing to the presence of round holes in them, look something like flutes
or fifes.
[Illustration:
FIG. 104.—The Mother-of-pearl Moth (_Botys margaritalis_), with larva
(1) and injured pods.
]
The full-grown caterpillars burrow into the soil, where they hybernate
in a delicate web. _Remedy_: Compare the preceding species.
Family: =Tortricidæ= (_Leaf-rollers_).
Small, thick-set moths (Fig. 105), with smaller palps than the snout
moths. Fore wings broad at the root, with straight or somewhat curved
outer margins. Hind wings as broad, or even broader, than the fore
wings. When at rest the fore wings lie in a roof-like way. They usually
possess many characteristic markings. Hind wings greyish, without
markings. Antennæ thread-like. Caterpillars hairless, or only slightly
hairy; 16-legged: many kinds live in leaves, which they roll up; others
in twigs, buds, and fruits, which they hollow out.
The =Fawn-coloured Pea Moth= (_Grapholitha nebritana_ = _G. pisana_).
_Moth_ (Fig. 105): Length ⅜ inch; span of wings about ⅖ inch. Fore wings
fawn-coloured, with metallic sheen; alternating short, white, and dark
lines on the front margin. Hind wings black, with bronze sheen and white
fringe. _Caterpillar_: ⅓ inch long; 16-legged; pale green, with brown or
black head, neck-shield, and last body segment. The thoracic legs are
black. Dark warts on each segment. _Habits_: Compare the succeeding
species.
[Illustration:
FIG. 105.—The Fawn-coloured Pea Moth (_Grapholitha nebritana_).
]
The =Crescent Pea Moth= (_Grapholitha dorsana_).
_Moth_: Somewhat larger than the preceding species. Fore wings olive
brown, with many small short white lines on the front margin. A
yellowish white crescent on the middle of the hinder margin. Hind wings
brownish. _Caterpillar_: Nearly ⅖ inch long, 16-legged, orange yellow,
with brown or black head, neck-shield, last body segment, and thoracic
feet. Covered with brownish-yellow warts. _Habits_: The moths fly about
in large numbers round the pea blossoms, always a short time after
sunset. The female lays one, two, or at most three eggs, on a very young
pod, or on an ovary. In fourteen days the caterpillar is hatched, bores
into the pod, and attacks the peas. The opening made in the margin of
the pod closes up again. The pod generally ripens early. When it opens,
the full-grown caterpillars creep out, and become pupæ in the soil,
within a web, where the pupa lives through the winter. The peas attacked
are always covered, while in the pod, with the coarse-grained excrement
of the caterpillars, and are often united two or three together by web
fibres. _Remedy_: Deep digging of the soil before the winter, or, still
better, deep hoeing as soon as the pea crop is gathered in. In this way
many of the caterpillars or pupæ hidden in the soil will be destroyed.
Family: =Tineidæ= (_Leaf-miners_).
[Illustration:
FIG. 106.—The Larch Moth (_Coleophora laricella_).
]
These moths are the smallest of the Lepidoptera. Like the snout moths,
they have strongly developed labial palps, but are distinguished from
them by their small wings; the hind wings are especially small, and have
sharp tips. The extent of the wings is increased by a broad marginal
fringe. When at rest, the wings slope like a roof, and the fringe near
their tips is often turned upwards. Antennæ thread-like, tolerably
long—in the males of a few species may even be very long. Caterpillars
slightly hairy, with five, or, rarely, four pairs of pro-legs. To this
family belong the well-known =Clothes Moth=; the =Corn Moth=, living in
stored-up grain; and also—
The =Carrot Moth= (_Depressaria nervosa_ = _Hæmylis daucella_).
_Moth_: Length ⅖ inch. Span of wings rather over ⅘ inch. Fore wings
reddish-grey brown, blackish on the nerves, and with scattered whitish
markings. Hind wings more of a grey brown. Thorax and abdomen very
shiny, and somewhat brighter than the wings. _Caterpillar_: Nearly ⅖
inch long, tolerably thick, especially in the middle, and variegated.
Head, thorax, and last body segment shining black, the last two regions
with reddish-yellow margin, and the thorax, in addition to this, divided
into right and left halves by a longitudinal yellow line. The rest of
the body is olive green; a broad orange-coloured line divides it into a
darker dorsal and a lighter ventral side. On the back many ill-defined
warts of a shining black colour. _Habits_: In March and April many of
the carrot moths which have survived the winter come out of their
hiding-places; they only fly at night. The eggs are laid separately on
umbelliferous weeds, carraway, or carrot plants. The caterpillars are
first seen when the plants flower; they live on the flower-stalks, which
they bind together by a few threads, and devour the flowers and young
fruits, sometimes even the flower-stalks. The caterpillars are very
active, and let themselves down by a thread when disturbed. Usually they
are fully grown in five weeks, and then bore into the stalks of the
plant, where they become pupæ. It is not known whether there are one or
two generations. The caterpillars are found at very various times, from
May to August.
The =Diamond-back Moth= (_Plutella cruciferarum_ = _Tinea xylostella_).
_Moth_: About ¼ inch long; span of wings ⅗ inch. Fore wings small,
lancet-shaped, with long fringes. Ground colour yellowish brown, darkly
speckled. Hind wings brownish grey, small, strongly fringed. When at
rest the long fringes form a sharp backward and upwardly directed comb,
while the antennæ are applied together and stretched straight forwards.
_Caterpillar_: About ¼ inch long, tapering in front and behind. A
beautiful green, with a black head. Lives hidden under a very thin web
or under a few fibres, on the lower side of the leaves of cabbage, rape,
and other crucifers. _Habits_: The pupa lives through the winter; the
moths emerge in May, and fly about in the evening. Two generations; the
first generation of caterpillars in the first half of July, the second
in late summer. The second generation is particularly apt to be
destructive to cabbage. Pupæ found on the leaves of the plants attacked,
and surrounded by a thick web.
SIXTH ORDER: Hemiptera (HALF-WINGED INSECTS).
[Illustration:
FIG. 107.—Left pair of wings of a Bug.
]
The mouth-parts are modified into a sucking and piercing beak. Head
small. Legs usually slender, with two- or three-jointed feet. Wings are
absent in several species (_e.g._ bed bugs); in one section (_e.g._
fruit bugs) the fore wings are half of leathery, half of membranous
texture (Fig. 107); in others, all four wings are membranous (winged
plant lice), or the fore wings are somewhat harder than the hind wings
(frog-hoppers). Incomplete metamorphosis (p. 89). None of agricultural
importance except—
Family: =Aphidæ= (_Plant Lice_).
[Illustration:
FIG. 108.—The Bean Aphis (_Aphis papaveris_); a larva of the same
below.
]
Long, five- to seven-jointed antennæ. Long thin legs, no power of
springing. Sucking beak long and thin. In the same species there are
both winged and wingless aphides, mostly the latter. In autumn, male and
female specimens are found. After pairing, the latter lay their eggs,
which are destined to live through the winter. The aphides hatched from
these the following spring are all females, but are distinguished from
those of the previous autumn by producing living young, which contain at
the time of their birth the germs of a new generation. The number of
young produced by a single female, and the number of generations
appearing within the year, vary according to the species. There are
species in which each female bears from eighty to one hundred young, and
nine to sixteen generations succeed one another in the year. In autumn
males and egg-laying females once more appear. As a rule the eggs live
through the winter, but the insects themselves may also do this. I must
add that there are constant differences within the boundaries of the
same species according to the habitat, and especially in the species
which regularly wander, either from one plant to another, or from the
leaves to the roots. But since the species injurious to agriculture do
not migrate in this way, nothing further need be said on the point. As
aphides suck plant juices during the whole of their lives, and have
enormous reproductive powers, they are very destructive. They suck from
stems and leaves the juices which would otherwise be used by the plants
themselves for growth or for the production of flowers and fruit, and
bear young, which bore their beaks into the same part in the immediate
neighbourhood of their mother, and quickly begin to multiply in their
turn. In this way, colonies consisting of a hundred or more individuals
are regularly formed (_e.g._ on peas, beans, roses). A plant part
attacked in this way shrivels for want of nourishment, and the aphides
upon it would die if they did not wander elsewhere. The third generation
usually contains, not only wingless individuals, but also others which,
after repeated moults, fly away and start a new colony in another plant.
Since aphides have many enemies (starlings, sparrows, grasshopper
warblers, etc., lady-birds and their larvæ, drone fly larvæ, lace fly
larvæ), and are often killed in large numbers by wind and rain, it only
occasionally happens, particularly in dry summers, that they entirely or
largely destroy the plants they infest. They injure plants, not only by
drawing away their nourishment, but also by the separation of a sugary
sticky fluid from the anus. If the minute drops of this fluid fall from
the upper parts of an infested plant to the lower (garden and field
beans), or from the leaves of an infested tree to the plants growing at
its foot, or, as sometimes happens, are carried by the wind to more
distant plants, great damage may be caused. The fluid evaporates and
leaves behind a shining sticky substance, which closes up the stomata of
the leaves, and partially checks exchange of gases (assimilation and
respiration). Particles of dust, sand, and smoke carried by the wind,
and also the cast skins of the aphides, stick to the surface of the
leaves and render exchange of gases still more difficult. The leaves
develop brown dirty patches, and die off. Besides this, the spores of
disease-producing fungi, carried by the wind, stick very easily to the
places covered by the sweet fluid, and readily germinate in it. Aphides
may thus be the indirect cause of several diseases (_e.g._ smut). These
insects are destructive, therefore, to other plants than those infested
by them. _Remedies_: Spraying with any one of the fluids destructive to
them—soapy water; a decoction of quassia chips; tobacco water, not too
concentrated; Nessler’s fluid (1½ ozs. soft soap, 2¼ ozs. tobacco
mixture, 2 ozs. fusel alcohol, half a pint ordinary alcohol, diluted
with rain water up to a quart: when used, mix with one-fifth the
quantity of rain water); Koch’s fluid (2 lbs. soft soap dissolved in
half a gallon of hot water; ½ lb. of quassia chips extracted for twelve
hours in 5 quarts of rain water, and the fluid thus obtained boiled and
filtered. It is then added to the soap water, and the whole brought up
to 10 gallons by addition of rain water). Spraying with one of the
above-named fluids must be renewed in a short time, so as to reach all
the aphides wherever possible; if even a few remain untouched, there
will soon be a large number again. A warm evening is best for the
spraying. Infested plants can also be strewn with finely powdered
substances, or these may be scattered over them by means of a small
bellows. Since such substances should remain on as long as possible,
they should be used after rain or early in the morning, when the dew is
still on the leaves. Among powdered matters suitable for the purpose,
the following may be named: gypsum, lime, tobacco, wood-ash, insect
powder (prepared from the flower-heads of Persian species of
chrysanthemum and from tansy heads). It must also be pointed out, that
these remedies must be employed as soon as the insects begin to show
themselves in considerable numbers; it is not desirable to delay till
the infestation has made considerable headway, as it is then much more
difficult to get a satisfactory result. In some cases, it is desirable
to cut off and burn or otherwise destroy much infested parts, or those
parts on which the insects first begin to multiply (_e.g._ early cutting
off of the tips of the stems in field and garden beans).
The species of aphis which most commonly occur upon cultivated plants
are:—The =Bean Aphis= (_Aphis papaveris_), ¹⁄₁₂ inch, black; on the tips
of the stems of field and marsh beans, also on poppy, turnips, lettuce,
and on several wild composites and umbellifers. The =Pea Aphis= (_Aphis
ulmariæ_), ⅛ to ⅙ of an inch long; green; July to September on peas,
chickling peas, and several wild leguminous plants; very destructive.
The =Corn Aphis= (_Aphis cerealis_), ¹⁄₁₂ inch, green or reddish brown,
also reddish brown with green abdomen; June to August on rye, barley,
oats and several grasses; sucks the axis of the ears, and the
flower-stalks; as the (black) eggs remain on the stubble during the
winter, it is advisable to plough this deeply in immediately after
harvest. The =Oat Aphis= (_Aphis avenæ_), ¹⁄₁₂ inch, dark green,
speckled with white; on oats and barley, scarcely ever on the ears, but
on the leaf-sheaths and the upper sides of the rolled-up leaves. The
=Hop Aphis= (_Aphis humuli_), ¹⁄₁₂ inch, green; on the under side of the
hop leaves, and, when very abundant, on the scales of the fruit. The
=Cabbage Aphis= (_Aphis brassicæ_), ¹⁄₁₂ inch, dark green, speckled with
grey; from May to September on all kinds of cabbage, and also on other
crucifers.
SEVENTH ORDER: =Physopoda= (BLADDER-FOOTED INSECTS).
Very minute insects, possessing a characteristic jaw apparatus, with
which they pierce the outer skin of leaves or the parts of flowers, and
suck their juices. The four small wings have long fringes at their
edges; the fore wings are tolerably hard. The ends of the feet do not
possess claws, but small bladders or suckers. The metamorphosis is
incomplete. In some years, one or other of the species may increase to a
very large extent, and these minute insects then fly about in swarms,
especially on very hot days; and they also wander about in large flocks.
If they settle on the face or hands of human beings, they cause a
disagreeable and persistent itching, as they continually walk about.
[Illustration:
FIG. 109.—Corn Thrips (_Thrips cerealium_).
]
The =Corn Thrips= (_Thrips cerealium_), ¹⁄₁₂ inch. Dark brown to black.
Male wingless. Female with small wings bending outwards at their tips
(Fig. 109); fore wings horny, hind wings membranous. Larva orange
yellow; head, prothorax, and tip of the abdomen, black. After the last
moult it becomes yellowish white, and acquires scale-like wings.
Hybernates in the adult condition; lays its eggs on various grasses,
also on different grain-plants. The larvæ, and, later on, the perfect
insects are found in large numbers sucking the ovaries of flowering corn
(wheat, rye, barley); as a result of which the ears do not fully
develop, but wither away. _Remedy_: Deep ploughing of the stubble, by
which the hybernating individuals are destroyed.
The =Elder Thrips= (_Thrips sambuci_) lives in elder, and sometimes also
multiplies in very young field beans, the leaves of which blacken and
shrivel up in consequence.
The =Flax Thrips= (_Thrips lini_) often injures flax.
EIGHTH ORDER: =Diptera= (FLIES).
Mouth-parts elongated, adapted for sucking or piercing. Fore wings
developed, rarely absent. Hind wings absent, as such,—altered into
club-like bodies (balancers or halteres) often covered with scales.
Metamorphosis complete. Larvæ always legless; most have biting
mouth-parts and no distinct head (maggots); the head-bearing dipterous
larvæ possess similar mouth-parts. The last become obtectate pupæ (p.
93), while the headless larvæ become pupæ within the larval skin.
Family: =Culicinæ= (_Gnats_).
Slenderly built, with long, thin legs. An elongated piercing proboscis
in the female. The male with feebly developed mouth-parts, and
feather-like antennæ. Both sexes suck up water and plant juices, and the
female blood as well; hence only the latter bites, especially at night.
They hybernate in the adult condition in cellars, barns, etc. The female
lays 250 to 300 eggs on any floating object in stagnant water (pools,
ditches, water-vessels). The larvæ (with large head, well-developed
prothorax, and a breathing-tube on the abdomen) live in water, as do the
pupæ. Several generations annually; especially in damp summers and
districts where the draining of the soil leaves much to be desired.
Although sand flies torment our domestic animals more than gnats, yet
these also may be very troublesome to them. They principally attack the
less hairy parts of the body (inner side of the ears, nose, mouth,
corners of the eye, arms, sexual parts). _Remedies_: Thorough draining
of the soil. Washing the domestic animals to be protected with a vinegar
extract of walnut leaves; rubbing with walnut leaves. Wherever possible,
any sores should be covered up, as they attract gnats, sand flies, and
flies; or the skin near them may be painted with turpentine or very
dilute carbolic acid. This is the less to be neglected, as several kinds
of flies eagerly lay their eggs in the sores of domestic animals.
Family: =Gallicolæ= (_Gall Gnats_).
[Illustration:
FIG. 110.—The Wheat Midge (_Cecidomyia tritici_), female.
]
Small gnats with large broad wings, much narrowed at the root, rounded
at the tip, and generally rough with hairs. Feelers made up of a large
number of spherical or cylindrical joints, covered with spreading hairs.
Proboscis short, legs long. The female has an ovipositor, with which she
inserts eggs in any part of a plant. At this particular spot a luxuriant
growth of vegetable tissue takes place later on, of varying extent, and
even forming a regular gall. The species of gall gnat are usually
brightly coloured, often red or yellow; these colours are lost, however,
in dried specimens. The larvæ are spindle-shaped, yellowish white,
yellow, or red; they become pupæ either in the soil or within the part
of the plant which they inhabit. Several species are destructive to
fruit-tree culture or forestry; I mention here only the most destructive
kinds which attack cultivated plants.
The =Hessian Fly= (_Cecidomyia destructor_).
[Illustration:
FIG. 111.—Plant of Barley, attacked by Hessian Fly. The pupæ at _a_.
]
Female about one-eighth of an inch long, male somewhat smaller. The
former velvety black, with black hairs, red belly, and red markings;
wings greyish; antennæ one-third the length of the body. Male black,
with reddish-yellow hairs, dirty red belly, and red markings. The name
“Hessian flies” was given in North America, during last century, because
it was believed they were introduced from Germany, in 1778, by Hessian
soldiers, in their straw. It is still very destructive in North America,
also in Germany, Russia, England, and Scotland. _Habits_: During April
or May, on warm still evenings, the female lays her eighty or ninety
eggs, singly or in pairs, on the lowest leaves of the still very short
haulms of rye, wheat, and barley. Eight days, on an average, after this
the maggots, which are at first oblong and spotted with reddish yellow,
are hatched, and glide down into the leaf-sheath, where they begin to
suck the haulm. They gradually alter their shape, becoming ovoid, and
transparent with the exception of the large yellowish white, quite
opaque fat body. They soon become pupæ (Fig. 111), which look like
grains of linseed, and are found in summer on the haulms of the ripe
grain. The presence of the constantly sucking larvæ causes great and
injurious distortions of the plant, especially obvious during the
flowering time, and for a short time afterwards. The haulm withers, and
shrivels at the point where the larvæ are present, _i.e._ above the
lowest node, or the lowest but one. At the time when the haulm begins to
turn yellow—that is, when the grain begins to ripen,—the larvæ become
pupæ; the haulm now easily breaks off at the infected spot; a strong
wind or heavy rain throws it to the ground. A badly infested field
looks, on this account, as if a herd of cattle had got loose and trodden
it all down, or as if the grain had been devastated by hail. Only a few
haulms bear ears containing normally developed grains. The flies emerge
from the pupæ in August and September, after which the females quickly
seek the winter corn, and lay their eggs singly or in pairs on the
leaves of the yet young plants. The larvæ creep between the leaf-sheath
and the still quite undeveloped haulm, and, in the case of small haulms,
a number of larvæ may collect together in the immediate neighbourhood of
the root, causing a spherical swelling. In many cases the plant dies if
its lower parts are inhabited by many larvæ. Before winter, the larvæ
attain their full size, leave the plants, and creep into the soil,
where, in the following spring, they become pupæ, from which flies
emerge fourteen days later. There are, therefore, two generations
annually. The _spreading_ of Hessian flies into regions where they were
formerly unknown may be caused by (_a_) straw containing the
linseed-like pupæ (straw for paper manufacture, packing, etc.); (_b_)
grain, among which are often found pupæ that have fallen out of the
haulms among the separated grain. _Remedies_: 1. Sowing the winter grain
as late as possible, so that the females of the summer generation when
they come out of the pupæ will find no winter-grain-plants in which to
lay their eggs. 2. Ploughing up the stubble immediately after harvest,
or else burning it, so that the pupæ found above the lower nodes are
either deeply buried or else burnt.
The =Scarlet Wheat Midge= (_Cecidomyia equestris_).
Female about ⅛ inch, male ¹⁄₁₂ inch; cherry red, with yellow hairs; back
of the thorax dark brown. Antennæ as long as the body in the male, half
as long in the female. On the wing from May till June; lays its eggs on
the leaves of grain-plants, at the base of the uppermost leaf by
preference. The blood-red maggots, when they are hatched, let themselves
slide down, and get between the leaf-sheath and haulm. Here they work
themselves into the haulm, making a longitudinal groove, the walls of
which swell more or less, and the end of which is indicated by an
obvious transverse thickening. The leaf-sheath hiding the attacked part
of the stem is usually more or less swollen. These gall-like outgrowths
take up a great deal of nutritious matter, not only from the affected
haulm but also from the plant at large, so that the regions not directly
attacked are retarded in their growth. The larvæ are full-grown at
harvest time, leave their hiding-places, and let themselves fall to the
ground, where the following spring they become pupæ, from which midges
quickly emerge. _Remedy_: After a year in which the insect has caused
great damage, the fields must be deeply ploughed in order to kill the
larvæ, which would otherwise live through the winter.
The =Wheat Midge= (_Cecidomyia tritici_).
[Illustration:
FIG. 112.—The Wheat Midge (_Cecidomyia tritici_): LI, larva in the
contracted, LII, the same in the extended condition. B, a wheat
flower: _a__{1} outer, _a__{2} inner glume, _b_, stamens; _c_,
brush-like stigmas; _d_, ovary; _l_, larvæ of the wheat midge. LI
and LII highly, B less highly, magnified.
]
Male ¹⁄₂₅ inch, female (Fig. 110) ¹⁄₁₇ inch, and possessing an
ovipositor which, when extended, is twice that length. Citron yellow,
slightly hairy; antennæ blackish, eyes black, legs dirty yellow. In
spring or early summer, the midges creep out of the soil in fields where
wheat has been planted the previous year. After pairing, the females
wander to fields where wheat or, more rarely, rye is growing. The
attacks of the midges commence when the ears begin to emerge from the
leaf-sheaths, and are continued throughout the flowering time of the
wheat. At night the female pierces the glumes with her ovipositor, and
lays three to ten perfectly transparent eggs in each flower. Each midge
lays eggs in several flowers, but two or more midges may use the same
flower for this purpose, so that as many as thirty maggots may be found
in one bloom (Fig. 112). The maggots, which are hatched out in a week,
creep down to the ovary and suck its juices. If many maggots live in one
flower it is sure to die, but if there are only a few it may produce a
grain, though this may be small. Ears infested by the maggots develop
yellow spots later on; many ears remain quite empty, and consequently
thin and upright. Full-grown maggot: ⅛ inch; straw yellow to chrome
yellow; quite transparent when very young. Is fully developed in three
weeks, and then lets itself fall to the ground (July or August). Becomes
a pupa the following spring; fourteen days later the midge escapes.
Family: =Rostratæ= (_Crane Flies_, _Daddy Longlegs_).
[Illustration:
FIG. 113.—The Daddy Longlegs, or Common Crane Fly (_Tipula oleracea_).
Left, the male and the maggot; right, the female and the pupa.
]
These very long-legged gnats live on the juices of plants, and do not
sting. The larvæ are legless, without a hard well-marked head; those of
most species live in mouldering plant parts (_e.g._ rotten wood), or the
decaying manures of our fields and meadows. A few species, however, are
very destructive, since they injure roots and other parts of cultivated
plants. The adult and larval stages of all the injurious kinds are not
yet distinguished. We know that the larvæ of the yellow and spotted
_Tipula maculosa_ are chiefly destructive in sandy soil; while more
binding clay soil and rich garden earth are infested by the larvæ of
_Tipula oleracea_ (Fig. 113), and damp meadows by those of _Tipula
paludosa_. The two last-named species are very much like one another;
grey or greyish brown with bright brown wings, having dark front margin.
Much is still unknown about the habits of “crane flies”; my researches
relate to the =Yellow-spotted Crane Fly= (_Tipula maculosa_). The adults
fly about in swarms during summer, usually from the beginning of June,
in the fields where the larvæ lived in spring. They lay their eggs
either in the same fields or (usually) in others, and are blown about
for long distances by the wind. Where the flies settle they lay each
time two or three black ovoid eggs, bent like a sickle, and repeat this
till all the eggs (200 to 250) are laid. Those fields which have
previously been grass land are the most infested by the crane flies. The
larvæ are headless, grey to lead coloured, with small prickles at the
hinder end of the body, and they first appear, in large numbers, under
the pieces of turf which are left behind in such fields, and which
appear to be the centres from which the destruction of the standing corn
begins. The larvæ are hatched out in summer, during the later part of
which, and during autumn, they devour plant roots; after hybernating,
they again attack the underground parts of plants the following spring.
They devour most readily the roots of grass and corn, but also those of
clover, rape, and several other plants, including some found in flower
and kitchen gardens. They are mainly injurious either in autumn or
spring, according to the nature of the plants attacked. Young
grain-plants are killed by them, older ones usually not. On fields where
winter corn grows they therefore do most damage in autumn, while this is
the case in spring on land where summer corn is cultivated. They are
sometimes harmless, since they can also feed on roots left behind in the
ground. The larva do not limit their ravages to underground parts; in
the evening, and also in the daytime during dark damp weather, they
devour parts of the first leaves of very young corn plants, though the
damage thus effected is often inconsiderable. In May the larva is ready
to pass into the pupa stage; it comes near the surface and becomes a
brown pupa, bearing small spines on the abdominal rings. After a rest of
fourteen to seventeen days, the pupa works its way upward till the front
part of its body sticks out of the soil. The fly then escapes.
_Enemies_: Mole, shrews, wagtails, grasshopper warbler, rook, gulls.
_Remedies_: When the maggots are very destructive in gardens they may be
collected, preferably in wet weather, since they then leave the soil
during the day. If they appear to an injurious extent on summer corn,
the fields should be rolled in April (either with the ordinary or the
spiked roller). At the time (June) when the crane flies swarm about the
fields and meadows in flocks, thousands of individuals can easily be
caught with a net.
Family: =Muscæformes= (_Gnat Flies_).
Gnats with relatively short legs, and antennæ which are in any case
shorter than the body, and are usually quite short and cylindrical,
possessing, however, six or more joints, while the antennæ of true flies
usually have only three joints. The gnat flies form, as it were, the
transition between the slender gnats with their long legs and antennæ,
and the more thick-set flies, the legs and antennæ of which are short.
Here belong the genera of =Shade Gnats= (_Sciara_, e.g. _Sciara Thomæ_,
the larvæ of which often wander about in companies, as the so-called
=Army Worm=), the =Sand Flies= (_Simulia_), and the =Hair Gnats=
(_Bibio_, _e.g._ the =Garden Hair Gnat=, _Bibio hortulanus_, the larva
of which gnaws the roots of plants, especially in humous garden soil).
The =Sand Flies=, or =Mosquitoes= (_Simulia_),
have thick-set bodies, short legs, and short nine or ten-jointed
antennæ; they are from ¹⁄₂₅ to ⅕ of an inch long, and have a short but
sharp proboscis, with which they suck up the flower juices which
constitute their chief food. But the female also sucks the blood of
human beings and animals, making herself exceedingly annoying in this
way. Its larval state is passed through in stagnant water; its
appearance is therefore local, and is especially favoured by damp
summers. The mature sand flies are found from early spring or through
the whole summer; several generations succeed one another in the same
year. Sand flies often appear in swarms, containing thousands of
individuals. Since the female eagerly creeps into the ears, noses, and
corners of the eyes in horses and oxen, she is extremely annoying and
even dangerous. Her bite produces a smarting sensation, and may cause
actual boils to form in the skin. When a large swarm of sand flies
settles on a herd of cattle or on some horses, these animals become
maddened and furious; they often rush wildly round for so long that they
fall down dead. _Simulia reptans_ is a common British form. _Remedies_:
Compare what is said on p. 165, about gnats. Sand flies can usually be
kept from horses’ ears by means of ear-caps.
Family: =Tabanidæ= (_Gad Flies_).
[Illustration:
FIG. 114.—The Rain Breeze Fly (_Hæmatopota pluvialis_).
]
Large or medium-sized flies with thick-set body, large broad head, flat
abdomen, and strong legs. The proboscis is less developed in the male,
which lives merely on plant juices, than in the blood-sucking female.
The cylindrical whitish larvæ live in earth, and are harmless. But the
female insects bite human beings, and the larger kind attack horses and
cattle in such a manner that blood-drops may be seen on the ground under
the animals attacked, if these remain for a time in the same spot. There
belong to this family: 1. The =Breeze Flies= (_Tabanus_), large insects
up to ⅘ inch long, which are seen flying about with a buzzing sound over
meadows and fields in the sunshine (=Ox Fly= = _T. bovinus_; =Horse Fly=
= _T. autumnalis_). 2. The =Lesser Breeze Flies= (_Hæmatopota_), smaller
and more slender, with grey wings, bite most before a storm and in hot
sultry days. 3. The =Blinding Breeze Flies= (_Chrysops_), as large as
the Lesser Breeze Flies, but broader, with shining golden-green eyes and
wings marked with black. _Remedies_: Compare p. 165, and above; draining
the soil, however, is no good here.
Family: =Muscidæ= (_True Flies_).
These are flies with three-jointed antennæ, constructed on the type seen
in the common house fly. Here are included the =Caterpillar Flies=
(_Tachina_), the =Flesh Flies= (_Sarcophaga_), =Common Flies= (_Musca_),
=Flower Flies= (_Anthomyia_), =Green-eyed Flies= (_Chlorops_), etc.