The Moths of the British Isles Second Series/Chapter 7
GEOMETRIDÆ.
Caterpillars of this family of moths, with very few exceptions, have only two pairs of claspers or prolegs; when there are more than four claspers, the extra ones are only rudimentary and therefore useless. In moving from place to place the caterpillar stretches out to its full length, first to one side and then to the other, as though measuring the distance. When a hold is secured with the true legs the body is arched and the claspers are brought up almost to the point held by the true legs; the latter are then thrust forward and the measuring business proceeds as before. Some kinds perform the looping manœuvre very deliberately, but others at a quick rate. In common parlance among British entomologists the caterpillars are called "geometers" or "loopers," but to our American confrères they are known as "measuring-worms" or "span-worms."
Most of the caterpillars feed openly on the foliage of trees, shrubs, or low-growing herbs, and the majority remain upon their respective plants during the day.
A large proportion of the moths may be obtained in the daytime, either by beating or otherwise disturbing the foliage or herbage among which they hide; several kinds rest on tree trunks, palings, rocks, walls, etc., where they are sometimes conspicuous, but more frequently not easy to distinguish from their surroundings. On the whole, members of this family are more available to the day collector than are those of the Noctuidæ. Although several species occasionally visit the sugar patch, such species are, as a rule, obtained more readily and in larger numbers by other methods. Brilliant light has a great attraction for many of the moths, some are more often captured at gas or electric lamps than in any other way, and among these are the migratory species.
Staudinger divides the family into the following subfamilies:—
- Geometrinæ (= Geometridæ, Meyrick).
- Acidaliinæ (= Sterrhidæ, Meyrick).
- Larentiinæ (= Hydriomenidæ, Meyrick).
- Orthostixinæ (not represented in Britain).
- Boarmiinæ (= Selidosemidæ, Meyrick).
Except as regards the Larentiinæ, I have largely adhered to Staudinger's arrangement of genera in each of the above subfamilies.
The typical genus of Larentiinæ would be Larentia, Treit, to which something over two hundred species are referred by Staudinger, among which are upwards of sixty that occur in the British Isles. Following some of the later generic changes, I find that none of our species are left in Larentia, but a few fall into Hydriomena, Hübner, and therefore Hydriomeninæ has been adopted for this subfamily.
GEOMETRINÆ.
The Rest Harrow (Aplasta ononaria).
This greyish-brown moth has two darker, sometimes reddish, cross lines on the fore wings, and one such line on the hind wings. It is presumably only to be regarded as an accidental visitor to England. The first record was of a specimen captured in the Warren at Folkestone in July, 1866, and since that year others were obtained in the same locality, but apparently not more than about half a dozen altogether. None seems to have been recorded for over thirty-five years. The specimen, whose portrait is shown on Plate 38, Fig. 3, was obtained from Dresden.
Abroad, the range includes Central and Southern Europe, Asia Minor, Syria, and Armenia.
The Grass Emerald (Pseudoterpna pruinata).
When freshly emerged from the chrysalis, the species represented by Figs. 6 to 8 on Plate 38 is of a beautiful blue-green colour, but in course of time a greyish shade creeps over the wings. The dark cross lines vary in intensity; in some specimens well defined and blackish, in others very faint, and hardly discernible; occasionally, the space between the lines on the fore wings is dark shaded; the whitish submarginal line is not always present. This species is the cythisaria of Schiffermiller, and the cytisaria of other authors.
The caterpillar (figured on Plate 41, Fig. 1, from a coloured drawing by Mr. A. Sich) is green, with three lines along the back, the central one dark green, the others whitish; a pinkish stripe low down along the sides, the points on the head and the first and last rings of the body are often pink also. It feeds on pettywhin (Genista anglica), also on broom (Cytisus scoparius) and gorse (Ulex); in captivity it seems to thrive on laburnum. Most frequently obtained in the springtime after hibernation.
The moth is to be found in June and July on moorlands and commons pretty well throughout the British Isles, but it seems not to have been noted north of Perthshire, in Scotland.
Odd specimens have been known to occur in late August or early September, but this is quite exceptional.
The Large Emerald (Geometra papilionaria).
This charming green species (Plate 40, Figs. 1 and 4) varies in tint and in the distinctness of the whitish wavy cross lines. In some examples, one or other of the lines is absent, and far more rarely there is but little trace of any of these markings. Occasionally, the discal mark is preceded by a whitish wedge-shaped spot on the fore wings (ab. cuneata, Burrows).
When newly laid the eggs are whitish, but soon change to greenish yellow, and finally to pinkish.
The caterpillar hatches in late summer, and feeds on birch, hazel, and beech, until the leaves begin to fall in the autumn; it then constructs a carpet of silk on a twig, and near a bud, upon which it takes up its position for the winter. When thus seen, its reddish brown colour, variegated more or less with green, assimilates so closely with its surroundings that the creature is not easy to detect. In the spring, when it awakens, the green colour increases in extent as the buds open and the leaves unfold; when they are fully expanded, the caterpillar sits among the foliage towards the tip of a twig, and is then almost entirely green, the reddish brown only showing on the head, slightly on the warts, and more distinctly on the hinder parts which are in touch with the twig. The chrysalis, enclosed in a flimsy silken web among the dead leaves, usually on the ground, is of a delicate green colour, dotted with buff on the back, and shaded with buff on the wing cases. The early stages are figured on Plate 42.
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The moth is out in June and July, and may occasionally be beaten out of a hedge or bush, but is most frequently obtained late at night, when it is active on the wing, and is attracted by a brilliant light.
The species occurs in woods, on heaths and moors, and in fens, throughout the British Isles, except the most northern parts of Scotland and the isles.
Abroad, the range extends to Amurland and Japan.
The Small Emerald (Geometra vernaria).
This species (Plate 40, Figs. 2 and 3) is smaller than the last mentioned, the green colour is of a softer tint, and the lines crossing the wings, two on the fore wings and one on the hind wings, are whitish, and not waved.
The caterpillar hatches from the egg in August, and after hibernation is to be found in May and June on Traveller's Joy or Old Man's Beard (Clematis vitalba). It is then green, with white dots arranged in lines along the back and sides; the head is deep reddish brown, and this, and also the first and last rings of the body, have raised points. Transformation to the greenish chrysalis is effected among the leaves, drawn together with silk. (Plate 44, Figs. 3 and 3a.)
The moth flies in the evening in July and August, and in the daytime may be disturbed, by the application of the beating stick, from its retreats in hedges, etc., where the food plant flourishes. Found in most of the southern and eastern counties of England, most frequently on the chalk; its range extends to Worcestershire. Except that it has been recorded as a doubtful inhabitant of Ireland, the species does not appear to occur elsewhere in the British Isles. The distribution abroad extends to Amurland.
The Blotched Emerald (Euchloris (Comibæna) pustulata).
When quite fresh, this moth (Plate 43, Fig. 1) is exceedingly pretty; the pale blotches vary a little in size, as also do the reddish marks upon them.
The caterpillar adorns itself with particles of its food as soon as it leaves the egg in July; after hibernation it uses the scales or husks of the oak buds for the same purpose. When stripped of its trappings it is found to be reddish brown in colour, with three slightly darker lines along the back; hooded bristles arising from raised brownish spots afford means for the attachment of the masquerading outfit, each moiety of which is covered with silk on one side before being placed in the required position. When beating oaks for larvæ in May and June, the contents of the umbrella or beating tray should not be too hastily thrown away, but allowed to remain therein for awhile, and closely watched for any movement among the litter. The spectacle of a cluster of oak bracts suddenly becoming active will certainly arouse curiosity, and on examination the cause of the commotion will frequently be found to be the caterpillar of this species. (Plate 41, Fig. 2; after Auld.)
The moth is out in June and July, and flies at dusk in and around oak woods. In the daytime it may be jarred from its perch in oak trees, and once I found a specimen on a fence in the Esher district. It has been known to visit light, and examples of a September emergence have been recorded.
As a British species it only inhabits England, and it has been noted from Staffordshire and Leicester, but seems to be rare in the midland counties generally. It is more frequently found in the southern and eastern counties.
Abroad, the range extends through Central Europe to Southern Sweden, S. Russia, N. Asia Minor, and Andalusia.
The Essex Emerald (Euchloris smaragdaria).
In some examples of this species (Plate 43, Figs. 2, 3) the green colour is brighter than in others, and very occasionally it is tinged with bluish; typically, there are white cross lines on the fore wings, but the inner one is not infrequently absent, and more rarely both are missing. The white central spot is very rarely absent, and the edges of the fore wings are yellowish.
The caterpillar feeds on the sea wormwood (Artemisia maritima), and adorns itself with fragments of its food plant in much the same manner as that of the species last referred to. Although obtained in the autumn in some numbers from its food plant, it seems to have been rarely met with in the spring after hibernation. It is, therefore, advisable to collect the caterpillars about September, and transfer them to plants of the garden Artemisia abrotanum, locally known as "Southernwood," "Old man," or "Lad's love," or, where available, wormwood (A. absinthium) will suit it admirably. Upon either of these plants the larvæ will hibernate, feed up in the spring, and become full grown about May. The early stages are figured on Plate 42, larva and pupa from photos by Mr. H. Main.
The moth is out in June and early July, but it is rarely seen in the open, although over sixty years ago a few specimens were put up from among grass and netted at St. Osyth; in later years an example or two have been taken at Sheerness in Kent. Possibly, others may also have been captured in one or other of the insect's haunts, but records are silent on the matter. Barrett mentions a specimen emerging in September, and the Rev. C. R. N. Burrows notes that part of a brood of caterpillars reared from eggs, and fed on A. absinthium, attained the moth state during the autumn. So far as concerns the British Isles it seems to be almost exclusively an inhabitant of the salterns, or sea marshes of Essex.
Abroad, the species occurs inland, and is not confined to the coast; its range extends eastwards to Siberia and Amurland.
The Small Grass Emerald (Nemoria viridata).
This species, represented on Plate 43, Figs. 5 and 6, is readily distinguished by its small size and the well-defined white cross line on each wing. In most examples there is a more or less distinct whitish inner line on the fore wings. Ab. mathewi, Bankes, has all the wings dusted with orange scales, more especially on the outer marginal areas. A few examples of this form were reared in 1905, with a number of normal specimens, from eggs laid by a female captured in South Devonshire.
The caterpillar (figured from a skin on Plate 44, Fig. 1) is green, roughened with whitish points; a dusky line along the middle of the back, marked on the front and end rings, also between the rings, with purplish red. Head, and first ring of the body, notched, the points reddish; last ring of the body pointed. When at rest on a twig it assumes a rigid posture, and the legs are tightly drawn together. It feeds on heather, sallow, and birch, but the general experience appears to be that in captivity it thrives best on a diet of hawthorn, and is especially partial to the young shoots. It may be obtained in July and August, and the moth comes out in the following May or June. In 1905, Mr. A. J. Scollick reared some caterpillars from eggs laid June 2nd, and hatched June 16th; all duly pupated, and a moth came up on December 20th of that year. Four others appeared in January and February, 1906.
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| 8, 9. Common Emerald. |
The Rev. F. E. Lowe states that in Guernsey the species occurs exclusively among furze on cliffs by the sea, and chiefly where the plant is cut down from time to time. In Britain it inhabits heaths and mosses, but is very local. It is found in the English counties of Hants (New Forest, etc.), Dorset (Poole Heath, etc.), Devon (Woodbury, Exeter district, etc.), Norfolk (Horning), Worcester (Malvern district, rare); also at Methop, Witherslack, and other localities in Westmoreland and Cumberland. Only doubtfully recorded from Scotland and Ireland.
Abroad, the range extends to Amurland, Corea, and China.
The Little Emerald (Iodis lactearia).
The green tint in this species (Plate 43, Figs. 4 and 7) is even more unstable than in others of the group. When quite fresh the wings can often only be described as whitish with a delicate green tinge, but even when the greatest care is taken to preserve it, the colour is apt to fade.
The caterpillar (Plate 44, Fig. 2, from a coloured drawing by Mr. A. Sich) is long and thin, with two points on the edge of the first ring, and one on the last ring, of a bright green colour, paler between the rings; the spots along the back are reddish, as also is the whitish-fronted deeply notched head. It feeds on the leaves of various trees and bushes, such as birch, oak, hawthorn, sallow, etc. It may be obtained by beating or searching from August to September.
The moth is out in May and June, in some seasons later, and may be beaten out of hedges, as well as from trees in woods. Generally distributed, and often common, throughout England, Wales, and Ireland. In Scotland it is locally common in Clydesdale, and occurs in other southern parts of that country.
Abroad, the range extends to Amurland, Corea, China, and Japan.
The Common Emerald (Hemithea strigata).
When freshly emerged from the chrysalis, this species (Plate 43, Figs. 8 and 9) is darkish green, but it soon fades to a greyish tint. Easily distinguished by its shape, and by the chequered fringes. It is the æstivaria of Hübner, and thymiaria of Guenée. The long, thin, green caterpillar is ornamented with reddish brown, the V-shaped marks on rings 5 to 8 are sometimes whitish; head, deeply notched, brown; the first ring of the body is also notched. It hatches from the egg in August, when it is said to feed on mugwort (Artemisia vulgaris), and other low plants; after hibernation it feeds on the foliage of oak, birch, hawthorn, rose, etc., and attains full growth in May or June. In late June and in July the moth may be put up from the undergrowth in woods, or from bushes in well-timbered hedgerows bordering lanes and fields. Specimens so obtained are poor in colour as a rule, and it is well, therefore, to rear the species from the caterpillar. (Plate 41, Fig. 3; after Hofmann.) This remark applies to all "Emeralds."
The species is often common in the south and east of England, and along the western side, including Wales, up to Cheshire and Lancashire, but it becomes local in Worcestershire and northwards. There are few records of it from Yorkshire, and its occurrence in Durham, Northumberland, and Scotland is doubtful. In Ireland it appears to be widely distributed, but scarce.
The range abroad extends to Amurland, Corea, and Japan.
[Thalera fimbrialis. A specimen of this Central European species (identified by the late Mr. C. G. Barrett) was taken on August 7, 1902, by Mr. C. Capper, from a blade of grass growing on a slope under Beachy Head, Sussex. The species is somewhat similar in appearance to H. strigata, but is larger; the hind wings are notched above the angle on the outer margin; the fringes of all the wings are chequered with red, and the antennæ of the male are bipectinated.]