cuticular structures-the scales (fig. 7)-that may be regarded as modified arthropod an “ hairs.” Such scales are not peculiar to the Lepidoptera-they are found also on many of the Aptera, on the Psocidae, a family of Corrodentia, on some Coleoptera (beetles) and on the gnats (Culicidae), a family of Diptera. The most distinctive structural features of the Lepidoptera are to be found in the jaws. The mandibles are mere vestiges or entirely absent; the second maxillae are usually reduced to a narrow transverse mentum which bears the scale-covered labial palps, between which project the elongate first maxillae, grooved on their inner faces, so as to form when apposed a tubular proboscis adapted for sucking liquid food. All Lepidoptera are hatched as the cruciform soft-bodied type of larva (fig. 1, a) known as the caterpillar, with biting mandibles, three pairs of thoracic legs and with a variable number (usually five pairs) of abdominal prolegs, which carry complete or incomplete circles of hooklets. The pupa in a single family only is free (i.e. with the appendages free from the body), and mandibulate. In the vast majority of the order it is more or less obtect (i.e. with the appendages fixed to the cuticle of the body) and without mandibles (fig. 1, c). Structure.-The head in the Lepidoptera is sub-globular in shape with the compound eyes exceedingly well developed, and with a pair of ocelli or “ simple eyes ” often. present on the vertex. It is able-number of Iiepidoptera take no food in the imaginal state; in these the maxrllae are reduced'or altogether atrophied. The second max'll ' ' ae are intimately fused together to form the labium< which consists only of a peduced ~men- tum, earing sometimes vestigial lobes lg and always a pair of b . palps. These have two or thrge segments an are I = -, ss clothed with scales. . § fl P Theform and direc-' '“ tion of the terminal I QT"§ =§§ § B segment of the labial #~' §§ " § palp afford valuable gi characters in classi- g § ¥ 3 hcation. In the thorax of the Lepidoptera the;§ " '* , , foremost segment or A. §§ , f' 1; pro thorax is very of ' g small, and notmov- i ' f 3 able on the meso- E “@' § Q thorax. In many §§ '. § families it carries a gi gg 199m .pair of small erectile if '":. ..plates-the patagia - *fi-ei" -which have been regarded as serially maxillae are so reconnected to the thorax by a relatively broad and membranous “ neck." The feelers are many-jointed, often they are complex, the segments bearing processes arranged in a comb-like manner " "X and furnished with 5 "', -, ~-, , it numerous sensory - . r ' . tt, ,, . X hairs (fig. 2). The ~ 'f~», i 5Q'f§ ~= L fel§ '~ ¢ complexity of the
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H . feelers is carried to its highest development <in certain male moths that have a wonderful power of discovering their females by smell or From Riley and Howard, Insect Life, 'vol. 7 (U.S. Dept. SOITIC 3.113-lOg0S S€I1S€Asn). Often the feelers are F IG. 2.-a, Feeler of Saturniid Moth (Telea excessively gomplex Polyphemus). b, c, Tips of branches, highly in male moths whgge magnified. homologous with the wings. The mesothorax is extensive; its scutum forming most of the dorsal thoracic area and small plates-tegulae—are often present at the base of the fore wings, as in Hymenoptera. The tegulae which are beset with long hair-like scales are often conspicuous. The meta thorax is smaller than the mesothorax. The legs are of the typical hexapodan form Fig. 4.-Arrangement of the jaws in a typical Moth. Somewhat diagrammatic and in part after E. Burgess and V. L. Kellogg. (Amer. Nat. xiv. xxix.). A, Front view of head. c, Clypeus. e, Compound eye. m, Vestigial mandible. l, Labrum. g, Galeae of 1st 'maxillae. " p, Labialpalp. Magnified, B., lhead. b, Base of first maxilla dissected out of the p, Vestigial palp. 1 g, Galea. Further magnified. C, Part transverse section showing how the channel (A) of the proboscis isiformed by the interlocking of the grooved inner faces of the Hexible maxillae. » t, Air-tube. n, Nerve. duced that they take no food in the imaginal state. The nature of the jaws has already been briefly described. Functional mandibles of peculiar form (fig. 3, A) are present in the remarkable small moths of the genus Microplefyx (or Eriovephala), and there are vestiges of these jaws in other moths of low type, but the minute structures in the higher Lepidoptera that were formerly described as mandibles are now believed to belong to the labrum, the true mandibles being perhaps represented by rounded prominences, , 2 not articulated with thehead-capsule. Throughout the order, as a whole, " - D the jaws are adapted for sucking "' L liquid food, and the suctorial prof boscis (often erroneously called- a
Y 9 “ tongue ) is formed as was -shown by ]. C. Savigny in 1816 by two
elongated and flexible outgrowths of the first maxillae, usually regarded as' representing the outer lo es or galeae (fig. 4, A, B, g). These structures are grooved along their inner faces and by means of a series of interlocking hair-like bristles can be A B joined together so as to form a After A. wana- um. um. f. f“bU1HE § UCl<@f (Hs 4, C)- Af fheif Nalunu. vol. 18). - extremities they are beset with club-FIG 3 . A' Mandibley and like sense-organs, whose apparent B 1st maxilla of Mic, op¢e, yx function is that of taste. Theproboscis when in use is stretched out in front of the head and inserted (Eriocephala). Magnified. 0' palp' d' Stipes” into the corolla of a flower or else-E iggxa e” grflggsfla of where, for the absorption of liquid nourishment. When at rest, the proboscis is rolled up into a close spiral beneath the head and between the labial palps (fig. 4, A, p). Only in th e genus Micropteryx mentioned above is the lacinia of the maxllla (as A. V/alter has shown) developed (fig. 3, B, c). The maxillary palp is usually a mere vestige (fig. 4, B, p) though it ns conspicuous in a few families of small moths. A considerwirh five segmented m, Muscle-fibres. Highly magnified. feet; the shins often bear terminal and median spurs articulated at their bases and-the entire'limbs are clothed with scales. 4 ' » The wings of the Lepidoptera may be said to dominate the structure of the insect; only exceptionally, in 'certain female rnoths, are they vestigial or absent (fig. 17). The forewing, with .its prominent apex, is longer than the, , . hindwmg, and the, i ' “' " 2 I A neuration in both ' 2 3 (see figs. 5 and 6) is, E § 4 for the most part; longitudinal, only a ' f few transverse ner-, * 33 vures, which are, in 2 4| fact, branches of the 4, median trunk, 7 52 6 marking off a discoidal areolet or “cell " (Hg. 5, a). 3 The five branches of . the radial nervure 3 (Hes-, 5. 6. 3) (see 8 HEXAPODA) are 41usuall resent in 7 2 T 52 51 if Y P f ' b t the Orewmg' U AfterA. s, 1>ae<ara, M¢~m. Nat. Amd. sei. vol. vii. the hindwing, in most families, has only a single radial nervure; its anal area is, however, often more strongly developed than that of the forewing. The two wings of a side are usually kept together during fiight by a few stout bristles-the frenulum-(fig. 5, f) projecting from the base of the costa of the hindwing and fitting beneath a membranous fold or a few thickened scales-the retinaculum-on the under surface of the forewing. In butterflies there is no frenulum, but a costal outgrowth' of the FIG. 5.-Wing-neuration of a Notodont Moth. 2, Subcostal; 3, radial; 4, median; 5, cubital; 7, 8, anal' nervures. a, Discoidal areolet or “ cell ”; f, frenulum. Note that the forewing has five branches (I-5) of the radial nervure, the hind wing one only. The
first anal nervure (No. 6) is absent.