The other three members of the family are very similar in appearance, the fore wings of all being marbled with shades of grey, relieved by touches of black and brown; and the hind wings, red or crimson, give the popular names to the species.

The Red Underwing flies in August and September, and is common in the southern counties of England, as well as in some of the midland counties; it may be often seen flying by day around willows.

[Ill.u.s.tration: FIG. 176.--THE RED UNDERWING.]

The caterpillar is similar in form to that of _Fraxini_, and when at rest by day on the bark of its tree it is very difficult to detect, so closely does it apply itself to the surface, and so perfectly does it imitate the colour of its surroundings. It feeds on the crack willow (_Salix fragilis_), sallow (_S. alba_), poplar (_Populus_), and plum (_Prunus_), and is full grown in June.

_The Dark Crimson Underwing_ (_Catocala Sponsa_)

This beautiful insect is represented on Plate XI (fig. 6). It will be observed that the black band crossing the centre of the hind wing is rather broad and sharply bent--an important feature, since it is the most serviceable distinguishing mark between this species and the Light Crimson Underwing (_C. Promissa_).

The caterpillar is similar in form and habits to those of _Fraxini_ and _Nupta_, and feeds on the oak. It is full fed about the beginning of June, when it changes to a chrysalis between leaves which it has spun together with silk.

The moth flies in July and August, and is common only in certain oak woods of the southern counties. It is particularly abundant in the New Forest, where scores may be taken in a single night by judicious sugaring.

There yet remain a few small families of the _Noctuae_, but we must leave them in order that we may give a proportionate share of our s.p.a.ce to the other great division of the larger moths--the _Geometrae_.

CHAPTER XX

_GEOMETRae_

We have already referred (page 28) to caterpillars that walk by a series of strides, alternately looping and extending their long and slender bodies. It is this peculiar characteristic of the larvae of the present division that suggested the name _Geometrae_--a term that signifies 'earth-measurers,' for they appear to measure the ground over which they travel in terms of their own length. We have also dealt with the peculiarities of structure in the case of these caterpillars--peculiarities which adapt them to this mode of progression; and we have now to make a selection from the various families of this important division for a more detailed description.

The _Geometrae_ include nearly three hundred species and sixteen families. The moths have slender bodies and full wings, and generally rest with the latter outspread. A few, however, repose with wings erect like the b.u.t.terflies, and a small number conceal their hind wings after the manner of the _Noctuae_.

Family--UROPTERYGIDae

_The Swallow Tail_ (_Uropteryx sambucaria_)

Our first family--_Uropterygidae_--has only one British representative, and that is the well-known Swallow Tail, so common in gardens and among hedgerows in the south of England. This species is shown on Plate XII (fig. 2), and the insect is so readily identified by the conspicuous 'tails' on the hind wings that no written description will be necessary.

The caterpillar is a most peculiar and interesting creature. Its colour is very variable, being either brown, olive, ochreous, or reddish; and it is notched or humped in such a manner that it exactly resembles a twig. This strange imitation is rendered still more remarkable by the att.i.tude a.s.sumed by the caterpillar when at rest. It fixes itself to a twig by means of its two pairs of claspers, with its body standing out at an angle in a perfectly straight posture; but its head is always supported by means of a very slender and almost invisible silk fibre. It feeds on a number of plants and trees, including elder (_Sambucus nigra_), blackthorn (_Prunus spinosa_), whitethorn (_Crataegus oxyacantha_), bramble (_Rubus fruticosus_), honeysuckle (_Lonicera Periclymenum_), and forget-me-not (_Myosotis arvensis_). It may be found feeding in the autumn, or hybernating in the crevices of the bark of trees in winter. In April or May it comes out again; and in June, in which month it is full grown, it binds together some fragments of leaves, and forms them into a little swinging hammock in which it changes to a brown chrysalis spotted with black.

Just at this time it seems to be particularly sensitive. In the caterpillar state it will strongly resent any kind of disturbance, and will give a blow to an intruder by suddenly swaying its body right and left; and while in its hammock a gentle irritation, such as a puff of wind from the mouth, will set it wriggling in a furious manner.

Family--ENNOMIDae

This family contains about twenty species, several of which rank among the commonest as well as the most beautiful of the _Geometrae_. Their wings are more or less angulated; and the antennae are generally pectinated in the males.

The larvae are generally humped and twig-like; and, as in the last species, the semblance is increased by the position they a.s.sume when at rest. The number of limbs varies from ten to fourteen, but where the claspers exceed two pairs, the additional two or four, as the case may be, are seldom used in walking.

_The Brimstone Moth_ (_Rumia luteolata_)

As soon as the warm evenings of May set in, this lively and bright little moth may be seen flitting about among our hedges at sunset; and it continues with us throughout the whole of the summer, but is particularly plentiful during the month of June.

The moth itself need not be described, since it is shown on Plate XII (fig. 3); but the caterpillar (fig. 25) must receive a pa.s.sing notice.

It varies considerably in colour, being either green, brown, or marbled with a mixture of shades of both these colours. It has a hump on the back of the seventh segment, and two more on the ninth, and possesses four pairs of claspers. It feeds on whitethorn (_Crataegus oxyacantha_), blackthorn (_Prunus spinosa_), and the apple (_Pyrus Malus_), and may be found on these trees throughout the summer.

Some believe that there are three successive broods of this insect each year, but it is doubtful whether this is invariably the rule, since both the moth and its larva are to be found without intermission throughout the season.

_The Light Emerald_ (_Metrocampa margaritaria_)

All the wings of this moth are very pale green, and crossed with a white band which is bordered with a darker green on the inner side. The fore wings have an additional transverse line just halfway between the former and the base, but this one is not so distinct. It flies in July, and is very widely distributed, and in some parts is very abundant.

[Ill.u.s.tration: FIG. 177.--THE LIGHT EMERALD.]

The caterpillar feeds in September, and again in May, after hybernation, on several of our forest trees, including the oak (_Quercus Robur_), elm (_Ulmus campestris_), birch (_Betula alba_), and beech (_f.a.gus sylvatica_). It is of a dingy olive colour, with a dark dorsal line, on each side of which is a row of white spots; and it has three pairs of claspers.

_The Scalloped Oak_ (_Crocallis elinguaria_)

This species is common and widely distributed, and may be seen flying at dusk towards the end of July and throughout August. It is represented in fig. 4 of Plate XII. The antennae of the male are strongly pectinated; those of the female are simple.

The caterpillar may be found in the autumn, and again in spring, feeding on the honeysuckle (_Lonicera Periclymenum_), whitethorn (_Crataegus oxyacantha_), blackthorn (_Prunus spinosa_), beech (_f.a.gus sylvatica_), and various fruit trees. It is full grown in June, when it turns to a chrysalis in a coc.o.o.n spun between leaves or moss on or near the ground.

It is of a greyish-brown or greyish-purple colour, and looks very like a piece of twig.

_The August Thorn_ (_Eugonia quercinaria_)

Our last example of this family is the August Thorn, represented in the accompanying woodcut. The fore wings are ochreous yellow, crossed by two nearly parallel lines of dark brown. In order to distinguish between this and one or two similar species it must be observed that both these lines are angulated near the costa, the inner one very sharply so; and between the two is a distinct brown spot near the costal margin. The hind wings are paler, and are crossed by an indistinct darker line. The antennae of the male are strongly fringed; those of the female are simple.

[Ill.u.s.tration: FIG. 178.--THE AUGUST THORN.]

The moth is very common in August and September, and is readily attracted by lights in the evening.

The larva is grey, marbled with reddish brown. It has three small humps on each of the sixth and seventh segments, two on the twelfth, and one larger one on the ninth. It feeds on the oak and various other trees during the month of June.

Family--AMPHIDASYDae

The seven British species of the family _Amphidasydae_ are generally to be distinguished by their rather stout abdomens, and the long s.h.a.ggy hair that covers their thoraces. The antennae of the males are pectinated, and those of the females simple; and in three cases the latter s.e.x is wingless.

The caterpillars have long and slender twig-like bodies, and are never provided with more than two pairs of claspers. The chrysalides terminate behind in a sharp spine, and are always to be found buried in the soil.

_The Brindled Beauty_ (_Biston hirtaria_)

Early in April, and sometimes in March, this moth may be seen in abundance, resting on the lime trees in and around our towns. In fact, so strongly marked is its partiality to the haunts of man in the neighbourhood of our great metropolis that it has received the name of the c.o.c.kney. The male is represented in fig. 5 of Plate XII, and the female may be distinguished from it by her simple antennae and larger body.

The caterpillar is coloured with alternate bands of dark purple brown and reddish brown. There is a yellow band on the front of the second segment, a row of yellow spots on each side, and two little bright yellow warts on the back of each segment. It feeds by night on lime (_Tilia vulgaris_), elm (_Ulmus campestris_), and various fruit trees, and often appears in such numbers that the foliage is almost completely devoured. During the daytime it may be seen resting on the bark, almost invariably fixed longitudinally on the trunk, where it looks like a natural ridge of the bark which it so closely resembles in colour. It may be found in June and July, and in August it changes to a chrysalis at the foot of its tree, just below the surface of the soil.