[Read before the Nelson Institute, 19th October, 1921; received by Editor, 26th October, 1921; issued separately, 17th February, 1923.]

The stone-flies, or Perlaria, form a very distinct order of insects, characterized by a combination of a primitive orthopteroid form of imago with an aquatic hemimetabolous form of larva. The perfect insects may at once be recognized by the following principal characters: Head wider than long, with rather small compound eyes placed wide apart; antennae long and many-segmented; mouth-parts mandibulate; no constricted neck region. Thorax with very distinct prothorax, the pronotum large and more or less flattened; meso- and meta-thorax quite separate and well developed, so that the wings are fairly wide apart at their bases; legs with short coxae, usually placed wide apart, the femora rather flattened, the tarsi three-segmented. Abdomen with ten distinct segments and a pair of anal cerci, which may consist of from one to very many segments; no appendix dorsalis. Wings in the position of rest folded longitudinally down the body, either more or less flatly or wrapped around it; the hindwing with a broad anal fan, which is folded under the rest of the wing when at rest. Ordinal characters in the wing-venation are the condition of M (which always has only two branches), the presence of a series of intercubital cross-veins in the forewing, and the position of Cu₂ just anterior to the cubito-anal furrow; in the hindwing there is always some amount of fusion between Rs and M close to the base of the wing, and 1A runs parallel and very close to Cu₂.

The perfect insects fly but little, and are usually to be found in close proximity to the streams in which their larvae live, either resting on rocks or hiding amongst the foliage fringing the water's edge, from which they can best be dislodged by sweeping.

The larvae are in general of a similar shape to the imagines, and are usually to be found in those parts of the stream where the water runs fastest, in cascades and rapids. Some are active, some very sluggish; but all alike possess great power of clinging to rocks against the rush of the water. In many cases external gills are developed on different parts of the body; the form and position of these gills afford valuable family characters within the order. The larvae are of economic value as trout-food.

Very little is known about the stone-flies of New Zealand, as the order has been greatly neglected both by collectors and by systematic entomologists. Only seven species have so far been described, though a season's careful collecting by Mr. W. G. Howes, of Dunedin, and myself has produced four times that number. The order is especially well represented in the colder parts of New Zealand, and a large number of the new species come from localities in Otago and Southland. These are being studied by Mr. Howes, and are not dealt with in this paper. The main object in

Moderately large insects, expanding from 50 mm. to 70 mm. Antennae from one-half to two-thirds as long as forewing. Pronotum somewhat heart-shaped, about as wide as long. Costal series of veinlets few and incomplete, there being always a long gap between the humeral veinlet and the next one. Medio-cubital cross-veins in forewing forming only a single row of cellules, only occasionally connected by a cross-bar.

Genotype.—Stenoperla prasina (Newman). New Zealand.

The only other described species of this genus is S. australis Till. from eastern Australia, but an undescribed species of a green colour has also been found in Queensland.

Fig. 1.—Wing-venation of Stenoperla prasina (Newm.) 1A, 2A, 3A, the three anal veins; Cu, cubitus; Cu₁, first cubitus, with its branches Cu_1a to Cu_1d; Cu₂, second cubitus; hm, humeral veinlet; M, media; M₁₊₂, M₃₊₄, its two main branches; M₅, its archaic basal posterior branch, which has become the most basal of the medio-cubital series of cross-veins: R, radius; R₁, its main stem; Rs, radial sector, with its branches R₂. R₃, and R₄₊₅; Sc, subcosta.

Stenoperla prasina (Newman). (Fig. 1.)

Chloroperla prasina Newman, 1845, Zoologist, vol. 3, p. 852. Hermes prasinus Walker, 1852, Cat. Neur. Brit. Mus., p. 206. Stenoperla prasina McLachlan, 1866, Trans. Ent. Soc., ser. 3, vol. 5, p. 354; Hudson, 1892, Manual Entom. N.Z., p. 106, pl. 16, fig. 3; Hutton, 1899, Trans. N.Z. Inst., vol. 31, p. 212; Hudson, 1904, N.Z. Neuroptera, p. 5, pl. 1, figs. 4–5; Tillyard, 1921, Proc. Linn. Soc. N.S.W., vol. 46, pt. 2, p. 233, pl. 15, fig. 9 and text-figs. 1, 4.

This species, easily recognized by its large size and by the bright-green coloration of the wings, is found in all parts of New Zealand where there is running water. Occasionally a yellow variety is found, in which the wings are somewhat shorter than in typical specimens.

Type in British Museum collection.

Needham, 1905, Proc. Ent. Soc. Washington, vol. 18, p. 109. Heteroperla Hare, 1910, Trans. N.Z. Inst., vol. 42, p. 30.

Genotype.—Austroperla cyrene (Newman).

This genus is distinguished from Tasmanoperla Till. by having, in the forewing, a definite anal angle, distad from which the posterior margin runs almost parallel with the costal margin of the wing, and also by the much weaker formation of the distal cross-veins.

Fig. 2.—Wing-venation of Austroperla cyrene (Newm.). (For lettering see fig. 1. except k, the strongly thickened second inter-anal cross-vein.)

Austroperla cyrene (Newman). (Fig. 2.)

Chloroperla cyrene Newman, 1845, Zoologist, vol. 3, p. 853. Perla (?) cyrene Walker, 1852, Cat. Neur. Brit. Mus., p. 168; McLachlan, 1874, Trans. N.Z. Inst., vol. 6, App., p. xcii (genus undet.). Stenoperla (?) cyrene Hutton, 1899, Trans. N.Z. Inst., vol. 31. p. 212. Heteroperla cyrene Hare, 1910, Trans. N.Z. Inst. vol. 42, p. 30.

Type in British Museum collection.

This common species varies greatly in size, specimens being found with an expanse from 20 mm. up to 30 mm. It may readily be distinguished by its folding the wings rather flatly down above its abdomen, with much less rolling of them around the body than in the Leptoperlidae, and also by its striking colour-pattern. The whole of the body is black, the wings blackish with weakly formed distal cross-venation, the forewing with a conspicuous cream-coloured humeral patch, which is continued more or less clearly as a pale stripe along part or whole of the costa. The legs are black, but the tibiae have a broad band of pale yellow occupying more than half their length. Cerci short.

It is of interest to note that a species of Tasmanoperla existing in Victoria, but not yet described, has a coloration closely similar to this species. There is also to be found in Otago a species of Zelandoperla, not yet described, which closely resembles it in coloration, but can be at once distinguished by its much longer cerci, as well as by its very different venational characters.

The larvae are very sluggish creatures, and frequently congregate at the edges of streams, under moist rocks or in wet trash, where other stone-fly larvae would not be able to exist. They are also unique in being able to stand removal from their natural habitat and living for quite a long time under abnormal conditions, even withstanding a considerable degree of desiccation. Probably they breathe through the integument generally, and perhaps also by means of gills placed internally within the anal opening.

To the characters given in the above key we may add the following: Insects of moderate to large size, from 1 in. to over 2 in. in expanse. Forewing narrow, three and a half times as long as wide; Sc lying close alongside R₁ for its whole length and forking at its tip; Cu₁ ending up about half-way between end of Cu₂ and apex of wing; 1A very close to Cu₂; only one inter-anal cross-vein connecting 1A with 2A. Both wings with a set of pterostigmatic veinlets present.

Genotype.—Leptoperla grandis Hudson.

Megaleptoperla grandis (Hudson). (Figs. 3, 4.)

Leptoperla grandis Hudson, Trans. N.Z. Inst., vol. 45, p. 51, 1913.

Hudson's description deals only with the size and coloration of this species, and fails to mention any of the very striking features of the venation, which separate it at a glance from all other described Perlaria. To the details already given in the generic key and definition the following specific characters may now be added:—

Head 3 mm. wide across the eyes, which are nearly black, but only 1.7 mm. long inclusive of the projecting clypeal shelf, which is itself only about half as wide as the rest of the head. Ocelli small but prominent; antennae with large bases set well forward in front of the eyes, the two basal segments considerably enlarged, the rest cylindrical, slightly hairy. Mouth-parts yellowish-brown, the palpi rather short.

Thorax: Pronotum sub-trapezoidal, 2 mm. long by 2.5 mm. wide, slightly wider behind than in front; the hinder edge with a narrow raised rim, as shown in fig. 4; median longitudinal furrow present but weakly formed. Meso- and meta-notum with a pale-yellowish median longitudinal band. Legs: Fore tibiae marked alternately with two transverse bands of dark fuscous and two of pale testaceous; hind legs with numerous soft hairs.

Abdomen: In the male the last two segments are paler than the rest, rich brown. The appendages are strongly curved and turn upwards behind the tenth tergite; viewed laterally their ends are flattened and well rounded; viewed from behind they are close together at their bases, but diverge apically, their tips appearing sharply pointed; the small copulatory

hook projects upwards between them but is considerably shorter. Cerci 3 mm. long, with numerous small ring-like segments, yellowish-brown with abundant short hairs.

Wings: Specific characters in the wing-venation are the presence of a complete series of costal veinlets in the forewing, and the very regular and complete formation of the distal cross-veins in both wings, associated with a certain amount of zigzagging of the branches of Rs and M₁₊₂. The mottled grey and whitish colouring of the forewing is continued on the distal two-thirds of the costa of the hindwing, including the pterostigma; the rest of the hindwing is whitish-subhyaline.

Fig. 3.—Wing-venation of Megaleptoperla grandis (Hudson) n. g. (For lettering see fig. 1.)
Fig. 4.—Head and pronotum of Megaleptoperla grandis (Hudson), ♂ (X 4.4).

Type in Mr. G. V. Hudson's collection; sex not specified.

Locality.—The type specimen was taken near Ohakune. Other localities for it are Tokaanu, Lake Taupo, where the larva is not uncommon under rocks in the Tongariro River (R. J. T.); Arthur's Pass and Dunedin (W. G. Howes).

Tillyard, Canadian Entomologist, Feb., 1921, p. 43.

To the characters given in the key we may add the following: Insects of small size, under 1 in. in expanse. Both wings with or without extra costal veinlets besides the humeral; pterostigma without veinlets; fork of Rs very short, terminal, usually without cross-veins, but sometimes with a single one as shown in fig. 6, forewing. Distal cross-veins irregularly placed, not very numerous; in forewing a complete series below Cu₁ right to its end, and only a single inter-anal connecting 1A with 2A. Sc not terminally forked, but with its apex turned upwards to the costa, and a cross-vein descending on to R₁ some little way before the apex.

Genotype.—Leptoperla confusa Hare.

Several species of this genus occur in New Zealand. Hare has described two species, both under Leptoperla—viz., Z. confusus (Hare), and Z. hudsoni (Hare).

Locality.—Common in many parts of New Zealand: Rotorua, Tarawera, Taupo; also Cass and Kingston (R. J. T.). Probably generally distributed.

Zelandobius unicolor n. sp. (Fig. 8.)

Resembles the preceding species in having the short extra distal veinlet in the costal space of the forewing, and in the excessive shortness of the terminal fork, which arises below the end of R₁, but differs from it in being a more robust insect, of somewhat larger size (forewing 9 mm.), with broader wings, of very different coloration, and with the antennae not so definitely moniliform, pale-brownish at base, darkening towards apex. Forewing subhyaline, tinged with pale-brownish, and along the costa with

Fig. 8.—Forewing of Zelandobius unicolor n. sp.

a suspicion of rose-pink; the veins yellowish-brown. Hindwing hyaline with the faintest tinge of yellowish-brown. The intercubital series of cross-veins in the forewing does not go beyond the end of Cu₂, and there are very few distal cross-veins, only two (rarely three) between each pair of main veins, as shown in fig. 9; those between Rs and M₁₊₂, M₁₊₂ and M₃₊₄, M₃₊₄ and Cu₁ respectively are very faintly shaded with pale fuscous. Cerci excessively short.

Type.—Holotype, apparently a male (abdomen shrivelled), in Cawthron Institute collection.

Locality.—Arthur's Pass, 18th January, 1920 (R. J. T.)

Insects of medium size, somewhat larger than those comprised [ unclear: ] in Zelandobius Till. Radial sector simple in both wings. Costal space with no extra veinlets beyond the humeral. Pterostigma without any veinlets. In the forewing the series of cross-veins below Cu₁ is incomplete distally. Hindwing with the fusion between M₃₊₄ and Cu₁ complete.

Genotype.—Leptoperla fulvescens Hare.

This genus differs from Zelandobius Till. in having Rs simple in both wings, in having the fusion between M₃₊₄ and Cu₁ complete in the hindwing, and in not possessing any extra veinlets in the costal space. It differs from Zelandoperla n. g., to which it is very closely allied, by not having any pterostigmatic veinlets, and by the distal series of cross-veins in the forewing below Cu₁ being absent from the distal part of the area in question.

Epicranium and pronotum blackish, the latter 1.4 mm. long by 2 mm. wide, and having the posterior lateral corners produced into two strong projecting spines (fig. 11, b). Appendages strongly upcurved, sharply pointed, with the shorter copulatory hook lying between them and having a narrowly blunt apex. Venation closely similar to that of N. howesi n. sp.

Female closely similar in size and general appearance to male, but having the posterior lateral corners of the pronotum cut off sharply at right angles, thus differing from those of N. howesi n. sp., which are rounded. Abdomen much slenderer than in N. howesi, reddish-brown in colour, darkest at base, and becoming bright-reddish apically. Ventral plate much less prominent than in N. howesi n. sp.

Types.—Holotype female, allotype male, and series of six paratype males in Cawthron Institute collection. (Holotype and allotype, 18th January, 1920, Arthur's Pass; R. J. T.)

Locality.—Arthur's Pass, January, 1920; taken both by Mr. Howes and myself.

Nesoperla trivacuata n. sp. (Fig. 12.)

♂. Forewing, 8.5 mm.; hindwing, 7 mm.; expanse, 18 mm.

In this species the head, thorax, and abdomen are all brownish-black, the pronotum having a definite median longitudinal impressed line on it. The pattern of the wings is very distinctive, as can be seen from fig. 12. The ground-colour of the forewing is either fuscous or brownish, and is interrupted by three large irregular areas, arranged more or less transversely at wide intervals across the wing, these areas being very pale and subhyaline. There is also sometimes a pale area of irregular shape close to the base. The size and shape of each of the three subhyaline patches varies greatly in different specimens: sometimes they are more or less oval, with fairly regular outline; sometimes more like transverse fasciae, with irregular outline. The typical and most common form has them very much as shown in fig. 12. Legs a bright medium brown. Cerci 3 mm., brownish. Appendages short, dark, slightly upcurved.

♂. Forewing, 11 mm.; hindwing, 9 mm.; expanse, 23 mm.

Closely resembling the male, but larger; forewings more fuscous. (Abdomen shrivelled, so that ventral plate cannot be seen.)

Types.—Holotype male (Lake Rotorua, 18th November, 1919; R. J. T.), allotype female (Tokaanu, Lake Taupo, 24th November, 1919, R. J. T.), and series of paratypes in Cawthron Institute collection.

Locality.—Appears to be generally distributed throughout New Zealand, but commonest in the North Island.

Varieties.—A variety frequently occurs in which the most basal of the three subhyaline patches is either obsolescent or quite absent. In one specimen this and the middle patches have coalesced.

Insects of medium to fairly large size. Radial sector simple in both wings. Costal space with no extra veinlets beyond the humeral. Pterostigma with a complete series of veinlets in both wings. In the forewing the series of cross-veins below Cu₁ is complete distally. Hindwing with the fusion between M₃₊₄ and Cu₁ complete.

Genotype.—Zelandoperla decorata n. sp.

As already stated under Nesoperla (q.v.), this genus is very closely allied to Nesoperla, but can be at once distinguished from it by the presence of the complete set of pterostigmatic veinlets in both wings, and also by the complete series of distal cross-veins below Cu₁ in the forewing. The pattern of the forewings in all species is much variegated.

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Zelandoperla decorata n. sp. (Figs. 13, 14a.)

♀. Forewing, 14.5 mm.; hindwing, 12.5 mm.; expanse, 30.5 mm.

Head short and wide, dull black, with pale-greyish pubescence. Median ocellus very small, the two lateral ocelli much larger, ruby-red, set on large black tubercles. Eyes, antennae, and mouth-parts dark brown. Behind the ocelli there is a transverse band of dark brown from eye to eye. Antennae 10 mm. long, basal segments very strong and large, second segment much smaller, but considerably larger than the others (fig. 14a).

Thorax.—Pronotum 1.5 mm. long by 1.9 mm. wide, with well-defined anterior, posterior, and median longitudinal grooves, the last-named slightly widened in the middle; colour dull black, with greyish-white pubescence (fig. 14a). Meso- and meta-notum shining black, with very slight pubescence. Legs dull brown to blackish, with soft pale hairs; femora mostly brown, with two patches of blackish, one at apex and one a little before; tibia with a black patch at base, followed by a pale-brownish

not so much enlarged as in Z. decorata, nor is the pronotum so definitely marked with grooves (fig. 14b).

Types.—Holotype female and series of paratypes in Cawthron Institute collection. (Holotype, Arthur's Pass, 16th January, 1920; R. J. T.).

Locality.—Arthur's Pass, January, 1920; taken by Mr. Howes and myself.

Some of the specimens show a distinct thickening of the pterostigma of the forewing, which tends to become unicolorous reddish-brown; in these cases the pterostigmatic veinlets become weak, and are not easy to see except with transmitted light.

Characters as in the key given above, to which may be added the following: Veinlets Sc₂ and R_1a present in pterostigma of forewing, Sc₂ only in that of hindwing. Intercubital space of forewing very wide; Cu₁ diverging strongly from M₃₊₄ at its apex.

Genotype.—Notonemoura latipennis n. sp.

Notonemoura latipennis n. sp. (Fig. 17.)

♂. Forewing, 6 mm.; hindwing, 4·8 mm.; expanse, 13 mm.

Head testaceous; eyes, ocelli, and two spots in front of lateral ocelli blackish. Antennae 4 mm. long, dull greyish-brown, with slender whitish annuli at base of each segment.

Thorax: Pronotum rectangular, wider than long, testaceous, with a narrow anterior transverse blackish band, a well-marked median longitudinal groove, and on either side a crescentic dark mark and an outer spot, the former merging posteriorly into a broad dark posterior transverse

band. Meso- and meta-notum blackish, touched with brown in front. Legs brownish; hind femora with a testaceous patch on basal half, and hind tibiae slightly darkened distally.

Abdomen (shrivelled) blackish, changing to brown apically. An exceedingly long and pointed organ, apparently the copulatory hook, projects upwards from the end of the abdomen.

Fig. 17.—Wing-venation of Notonemoura latipennis n. g. et sp (For lettering see fig. 1, except m-cu, medio-cubital cross-vein, and r-m, radio-median cross-vein, forming portions of the transverse cord or anastomosis.)

Wings subhyaline, unicolorous; venation very pale testaceous, almost whitish.

Type.—Holotype male in Cawthron Institute collection, also a second specimen from Karori, both taken by myself.

Locality. — Arthur's Pass, 16th January, 1920 (R. J. T.); Karori, Wellington, 6th December, 1919 (R. J. T.).

Characters as given in the generic key, to which may be added the following: Pterostigma with only one veinlet, Sc₂, in both wings. Cross-vein m-cu very long in forewing, obliquely placed to rest of transverse cord. Anal fan rather narrow.

Genotype.—Spaniocerca zelandica n. sp.

Spaniocerca zelandica n. sp. (Fig. 18.)

♀. Forewing, 9 mm.; hindwing, 7·5 mm.; expanse, 19 mm.

Head, including antennae and eyes, dull greyish-black.

Thorax: Pronotum subrectangular, slightly wider in front than behind, dull greyish-black. Meso- and meta-notum jet black, the former with a large bright-brown patch posteriorly. Legs dull-brownish, the hind femora with a pale band in middle, the hind tibiae pale basally, darker distally.

Abdomen black, tenth tergite testaceous; ventral plate projecting beyond end of abdomen in the form of a narrow subtriangular tongue, pale testaceous in colour.

Wings: Forewing subhyaline, slightly infuscated, the veins rich brown and narrowly shaded with fuscous; at about two-thirds of the wing-length there is a faint indication of a pale transverse fascia. Hindwing very pale