The family as a whole consists of Insects of unattractive appearance, although it contains some very elegant and interesting moths and numerous forms of structural interest. In the genus Thiridopteryx little transparent spaces on the wings occur as a character peculiar to the males; the spaces are correlative with a greater or less derangement of the wing-nervures. In some other forms there is a remarkable retinaculum, consisting of large scales, and this, too, is connected with a distortion of the wing-nervures. The Pyralidae—Pyralites of Ragonot,[[318]] Pyralidina of Meyrick—have recently been revised by two naturalists of distinction almost simultaneously; unfortunately their results are discrepant, Meyrick including Pterophoridae and Orneodidae, and yet admitting in all only eight families; while Ragonot does not include the two groups named, but defines seventeen tribes of the two families—Pyralidae and Crambidae—that he admits.
The Pyraustidae of Meyrick is an enormous division including the Hydrocampidae and Scopariidae of many authors, as well as the Pyraustinae proper and a small group of Ragonot's, the Homophysinae. The division Scopariinae is believed to be amongst the "most ancient" of Lepidoptera; the food of the larvae consists of moss and lichens. This group is widely distributed, being richly represented in Australia, New Zealand, and the Hawaiian Islands, as well as in Europe; and probably really occurs wherever their food-plants exist accompanied by a tolerable climate. The statistics of the distribution of this group, so far as at present known, have been furnished by Mr. Meyrick, as follows:—European region, about 25 species; Madeira, 3; St. Helena, 6; South Africa, 2 or 3; India, 9; Malayan region, 3 or 4; Australia, 24; New Zealand, 64; Hawaiian Islands, 50; North America, 17 (one of them European); South America, 10. The Hydrocampinae—the China-marks—are of great interest, as being amongst the few forms of Lepidoptera adapted for aquatic life. It is believed that all their larvae are aquatic, though of only a few is there much known. The diversity amongst these forms is of considerable interest. The habits of Hydrocampa nymphaeata were long since described by Réaumur, and have more recently been dealt with by Buckler,[[319]] W. Müller[[320]] and Prof. Miall.[[321]] Although there are some discrepancies in their accounts, due we believe to the observations being made at different periods of the life and under somewhat different circumstances, yet the account given by Müller is we feel no doubt substantially correct. The larvae when hatched mine in the leaves of a water-plant for a short time—thirty hours to three days according to Buckler—and are completely surrounded by water, which penetrates freely into their burrows; at this period the caterpillar breathes by its skin, the spiracles being very small, and the tubes leading from them closed and functionless. After this brief period of mining life, the larva moults and then constructs a habitation by cutting a piece out of a leaf, and fastening it to the under side of another leaf; it is thus provided with a habitation, but it is one into which the water freely enters, and the respiratory apparatus remains in the state we have described. The Insect passes through several moults, and then hibernates in the water. On its revival in the spring a change occurs, and the larva constructs a portable, or we should rather say free, habitation out of two large pieces of leaf of lens-shape, fastened together at the edges; but the larva has some method of managing matters so that the water can be kept out of this house; thus the creature lives in air though immersed in the water. A correlative change occurs in the structure of the skin and tracheal system. The former becomes studded with prominent points that help to maintain a coat of air round the Insect, like dry velvet immersed in water; the spiracles are larger than they were, and they and the tracheal tubes are open. One or two moults take place and the creature then pupates. There is a good deal of discrepancy in the accounts of this period, and it seems probable that the pupa is sometimes aerial, sometimes aquatic. Buckler's account of the formation of the case shows that the larva first cuts off, by an ingenious process, one piece of leaf, leaving itself on this, as on a raft; this it guides to a leaf suitable for a second piece, gets the raft underneath, and fastens it with silk to the upper portion, and then severs this, leaving the construction free; afterwards the larva goes through a curious process of changing its position and working at the two extremities of the case, apparently with the object of making it all right as regards its capacity for including air and keeping out water. He believes that Réaumur was correct in his idea that the larva regulates the admission of air or of water to the case in conformity with its needs for respiration. Müller calls special attention to the great changes in habit and in the structure of the integument during the life of this larva; but the reader will gather from what we relate as to various terrestrial Lepidopterous larvae, that these phenomena are not very dissimilar from what frequently take place in the latter; a change of habits at some particular moult, accompanied by great changes in the integument, and even in the size of the stigmata, being of frequent occurrence.
The larva of Nymphula stagnata, a close ally of H. nymphaeata, has aquatic habits of a somewhat similar but simpler nature; while N. (Paraponyx) stratiotata is very different. This larva is provided with eight rows of tufts of flexible branchiae, occupying the position of the spots or setigerous warts usual in caterpillars, and reminding one of the spines of certain butterfly-larvae, though they are undoubtedly respiratory filaments. These caterpillars protect themselves by forming silken webs or cases, or by adopting the case of some other larva, and are in the habit of holding on by the anal claspers, and rapidly and energetically moving the anterior parts of the body in an undulating fashion. The spiracles exist, but are functionless. The pupa lives under water, and has no branchiae; but three of the pairs of abdominal spiracles are open, and project from the body. Müller informs us that in a Brazilian Paraponyx these three pairs of spiracles were already large in the larva, though the other pairs were very small, or absent. He considers that the moth of this species descends beneath the water of a rapid stream, and fastens its eggs on the stems of plants therein. Cataclysta lemnata lives in a case of silk with leaves of duckweed attached to it, or in a piece of a hollow stem of some aquatic plant; it is believed to breathe, like H. nymphaeata, at first by the integument and subsequently by open stigmata; but particulars as to how it obtains the requisite air-supply are not forthcoming: the aquatic pupa breathes by three large abdominal spiracles like Paraponyx.
Musotimidae[[322]] is a small group of two or three genera found in Australia and Polynesia; and the Tineodidae also consist of only two Australian genera. Siculodidae is likewise a small Antarctic group, placed by Meyrick in Pyralidina; but his view is not accepted by Snellen and Ragonot. Epipaschiinae (formerly treated as a separate family) and Endotrichiinae are, according to Meyrick, subdivisions of the family Pyralidae proper, an enormous group of more than 100 genera. The Chrysauginae consist chiefly of American forms, and have not been treated by Meyrick; some of this group have been classed with Tortricidae or Deltoidae on account of the undulating costa of the front wings and the long, peculiar palpi. The Galleriidae are a small group including Insects that live in bees'-nests, and feed on the wax etc.; others eat seeds, or dried vegetable substances. Three out of our five British species of this family occur (usually gregariously) in bee-hives, and have the peculiar habit of spinning their cocoons together. The mass of common cocoons formed in this manner by Aphomia sociella is remarkably tough and enduring; portions of it are not infrequently picked up, and as the cocoons are of a peculiar tubular form their nature gives rise to some perplexity.
Phycitidae[[323]] is another very large assemblage of Insects with very diverse habits. The frenulum and retinaculum are similarly formed in the two sexes: the males frequently have the basal-joint of the antennae swollen; hence the term "Knot-horns" applied by collectors to these moths. The larvae of the species of Ephestia infest groceries, and most children have become to a slight extent acquainted with them amongst dried figs; that of E. kuehniella has become very injurious in flour-mills, its enormous increase being due in all probability to the fact that the favourable and equable temperature maintained in the mills promotes a rapid succession of generations, so that the Insect may increase to such an extent as to entirely block the machinery. Many of the Phycitidae feed on the bark of trees in galleries or tunnels constructed partially of silk. A very peculiar modification of this habit in Cecidipta excoecaria has been described by Berg.[[324]] In Argentina this Insect takes possession of the galls formed by a Chermes on Excoecaria biglandulosa, a Euphorbiaceous tree. The female moth lays an egg on a gall, and the resulting larva bores into the gall and nourishes itself on the interior till all is eaten except a thin external coat; the caterpillar then pupates in this chamber. The galls vary in size and shape, and the larva displays much constructive ability in adapting its home to its needs by the addition of tubes of silk or by other modes. Sometimes the amount of food furnished by the interior of the gall is not sufficient; the larva, in such cases, resorts to the leaves of the plant for a supplement, but does not eat them in the usual manner of a caterpillar; it cuts off and carries a leaf to the entrance of its abode, fastens the leaf there with silk, and then itself entering, feeds, from the interior, on the food it has thus acquired. Another Phycitid, Dakruma coccidivora is very beneficial in North America by eating large Scale-Insects of the Lecanium group, somewhat after the fashion of Erastria scitula; it does not construct a case, but shelters itself when walking from one scale to another by means of silken tubes; it suffers from the attacks of parasites.[[325]] Oxychirotinae, an Australian group, is interesting because, according to Meyrick, it possesses forms connecting the Pterophoridae with the more normal Pyralids.
Crambidae, or Grass-moths, are amongst the most abundant Lepidoptera in this country, as they include the little pale moths that fly for short distances amongst the grass of lawns and pastures; they fold their wings tightly to their body, and have a head pointed in front, in consequence of the form and direction of the palpi. They sit in an upright position on the stems of grass, and it has been said that this is done because then they are not conspicuous. Perhaps: but it would be a somewhat difficult acrobatic performance to sit with six legs across a stem of grass. The larvae are feeders on grass, and construct silken tunnels about the roots at or near the surface. The Ancylolominae are included in Crambidae by Meyrick and Hampson. Schoenobiinae[[326]] are included by Meyrick in Pyraustidae, but this view appears not to meet with acceptance, and the group is more usually associated with the Crambidae. Most writers place the anomalous genus Acentropus as a separate tribe, but it is associated by both Meyrick and Hampson with Schoenobius. This Insect is apparently the most completely aquatic of all the Lepidoptera, and was for long associated with the Trichoptera in consequence of its habits and of the scaling of the wings being of a very inferior kind. The males may sometimes be found in large numbers fluttering over the surface of shallow, but large, bodies of water; the females are rarely seen, and in some cases have no wings, or have these organs so small as to be useless. The female, it would appear, comes quite to the surface for coupling, and then takes the male beneath the water. The larvae have the usual number of Lepidopterous feet, and apparently feed on the leaves of plants below water just as Lepidopterous larvae ordinarily do in the air.[[327]] They have no trace of gills, and their mode of respiration is unknown. A great deal has been written about these Insects, but really very little is known. They are abundant, though local in many parts of North and Central Europe; some of the females have, as we have said, abbreviated wings, but how many species there are, and whether the modifications existing in the development of the wings are constant in one species or locality, are unknown as yet.
Fam. 42. Pterophoridae[[328]] (Plume-moths).—Elegant Insects of small size, usually with the wings divided (after the fashion of a hand into fingers) so as to form feathers: the extent of this division is diverse, but the hind wings are more completely divided than the front, which indeed are sometimes almost entire. The group is placed by Meyrick in his Pyralidina, but there are many entomologists who look on it as distinct. It consists of two sub-families, Agdistinae and Pterophorinae, that have been treated as families by many entomologists. The Agdistinae (of which we have a British representative of the only genus Agdistes) have the wings undivided. Pterophorinae have the hind wings trifid or (rarely) quadrifid, the front wings bifid or (rarely) trifid. The larvae of the Pterophorinae are different from those of Pyralidae, being slow in movement and of heavy form, covered with hair and living exposed on leaves; the pupae are highly remarkable, being soft, coloured somewhat like the larvae, and also hairy like the larvae, and are attached somewhat after the manner of butterfly-pupae by the cremaster: but in some cases there is a slight cocoon. There is, however, much variety in the larval and pupal habits of the Pterophoridae, many having habits of concealment of divers kinds. We have thirty species of these lovely Plume-moths in Britain. The family is widely distributed, and will probably prove numerous in species when the small and delicate Insects existing in the tropics are more appreciated by collectors.
Fam. 43. Alucitidae (Orneodidae of Meyrick and others).—The genus Alucita includes the only moths that have the front and hind wings divided each into six feathers. Species of it, though not numerous, occur in various regions. The larva and pupa are less anomalous than those of the Pterophoridae, though the imago is more anomalous. The caterpillar of our British A. polydactyla feeds on the flower-buds of honey-suckle, and forms a cocoon. The moth with wings expanded is about an inch across, and is a lovely object. It is not rare, though seldom numerous.
Fam. 44. Tortricidae.—Moths of small size, with a rather ample wing area, with the wing-fringes never as long as the wings are wide (long across), the hind wings without a pattern: the anterior nervure on the hind wings is simply divergent from that next to it, and the internal nervure, 1b, is very evidently forked at the base. The larvae inhabit their food, which may be rolled up or twisted leaves, or the interior of fruits and herbs, or galls, or even roots; they exhibit less diversity than is usual in other large series of moths; all have the normal complement of sixteen legs. This group is a very extensive one, but is much neglected owing to the great difficulties attending its study; it is not recognised in Hampson's Table of families given on p. [370], being there merged in Tineidae. It appears, however, to be a really natural group, and it is not desirable to merge it in the sufficiently enormous assemblage of the Tineidae till this has been shown to be necessary by the light of a greater knowledge of the external anatomy than we possess at present. The term Microlepidoptera is frequently met with in entomological literature, and should, we think, be confined to the two series Tortricidae and Tineidae. The Pterophoridae, and even the Pyralidae, have been, and still sometimes are, included under this term, but at present it seems best to limit its application as is here suggested.
Three great divisions are at present recognised; these were formerly called by Meyrick,[[329]] Tortricidae, Grapholithidae, Conchylidae; subsequently,[[330]] he has adopted the names Tortricidae, Epiblemidae, Phaloniadae. Lord Walsingham, who has devoted a great deal of time and study to the elucidation of this most difficult group, has suggested[[331]] that another change is desirable, and if so the nomenclature will be:—1. Tortricidae [or Tortricinae, according to the view that may be taken as to the group being family or sub-family]; 2. Phaloniidae [= the formerly used name, Conchylidae]; 3. Olethreutidae [= the formerly used name Grapholithinae = Epiblemidae, Meyr.]. We have upwards of 300 species in Britain, nearly 200 of which belong to the last division. The name Tortricidae refers to the habit the larvae of these moths possess of rolling up leaves, or twisting and distorting shoots and buds.