The Arctiidae (tiger moths, footmen, &c.) are allied to the Noctuidae, but their wing-neuration is more specialized, the sub-costal nervure of the hindwing being confluent with the radial for the basal part of its course. These moths (fig. 37) have gaily coloured wings, and the caterpillars are often densely covered with long smooth hairs. The pupae are enclosed in silken cocoons (fig. 38). The highest specialization of structure in this group of the Lepidoptera is reached by the Syntomidae, a family nearly allied to the Arctiidae, but with the sub-costal nervure in the hindwing absent. The Syntomidae have elongate narrow forewings and short hindwings, usually dark in colour with clear spots and dashes destitute of scales (fig. 40). The body, on the other hand, is often brilliantly adorned. The family, abundant in the tropics of the Old World, has only two European species.

Fig. 35.—Rothia pales. Madagascar.

Sphingides.

Fig. 36.—Aegocera rectilinea. Tropical Africa. Fig. 37.—Haploa Lecontei. N. America.
After Lugger, Riley and Howard, Insect Life, vol. 2 (U.S. Dept. Agr.).
Fig. 38.—c, Tiger Moth (Phragmatobia fuliginosa, Linn.). Europe. a, Caterpillar; b, cocoon with pupa. Slightly enlarged.

This group includes a series of families which agree with the Noctuides in most points, but are distinguished by the origin of the second median nervure of the forewing close to the first, or from the discocellular nervure midway between the first and third medians (see fig. 5). These neurational characters may appear somewhat insignificant, but such slight though constant distinctions in structures of no adaptational value may be safely regarded as truly significant of relationship. Several of the families in this group have lost the frenulum. In larval and pupal characters the Sphingides generally resemble the Noctuides, but in some families there is a reduction in the number of the larval prolegs. The egg is spherical or flat, upright only in the Notodontidae.

Fig. 39.—Halias prasinana. Europe.Fig. 40.—Euchromia formosa. S. Africa.

The Notodontidae are stout, hairy moths (figs. 5, 41, 42 a) with maxillae and frenulum developed. In the larva the prolegs on the hindmost segment are sometimes modified into pointed outgrowths which are carried erect when the caterpillar moves about. From these structures whip-like, coloured processes are protruded by the caterpillar (fig. 42 b) of the puss moth (Cerura) when alarmed; these processes are believed to help in “terrifying” the caterpillar’s enemies. Allied to the Notodontidae are the Cymatophoridae—a family of moths agreeing with the Noctuidae in appearance and habits—and the large and important family of the Geometridae. The moths (fig. 43) of this family are distinguished from the Notodontidae by their delicate build and elongate feet, the caterpillars (fig. 43, c) by the absence or vestigial condition of the three anterior pairs of prolegs. The two hinder pairs of prolegs are therefore alone functional and the larva progresses by “looping,” i.e. bending the body so as to bring these prolegs close up to the thoracic legs, and then, taking a fresh grip on the twig whereon it walks, stretching the body straight out again. Many of these larvae have a striking resemblance both in form and colour to the twigs of their food-plant. In some of the species the female has the wings reduced to useless vestiges. The family is world-wide in its range. The tropical Uraniidae are large handsome moths (figs. 44, 45), often with exquisite wing-patterns, allied to the Geometridae, but distinguished by the absence of a frenulum in the moth and the presence of the normal ten prolegs in the larva.

Fig. 41.—Notodonta ziczac (PebbleProminent Moth). Europe.
Fig. 42a.—Cerura borealis.N. America. Fig. 42b.—Larvaof Cerura (Puss Moth).
After Grote, Natural Science (J. M. Dent & Co.).
Fig. 43.—Geometrid Moth (Amphidasys betularia, Linn.). Europe. a, Large grey type; b, dark variety; c, caterpillar in looping attitude.