Ichthybotus bicolor n. sp. (Plate 19, and text-figs. 3–5.)
♂. Imago: Total length, 19 mm.; forewing, 16 mm.; hindwing, 6 mm.; expanse, 33 mm.
Head deep chocolate-brown; eyes blackish.
Thorax deep chocolate-brown; legs the same colour, except coxae and bases of the femora, which are paler. Foreleg 10·5 mm. long.
Abdomen deep chocolate-brown, faintly mottled with somewhat paler brown; in shape slender subcylindrical, slightly narrowed at 5–7, broadening again at 8–9; 9 much wider than 10, broader apically than basally. Cerci 23 mm. long, dark chocolate-brown, strongly formed, slightly hairy, the segments cylindrical with narrow black basal rings. Appendix dorsalis vestigial, 1 mm. long, with few segments.
Appendages of the same type as in I. hudsoni McL., but with the following differences: Forceps basis slightly shorter and cut-off obliquely on either side of its posterior margin, which, between the bases of the forceps, is cut straight off, not double-curved as in I. hudsoni McL.; pale brown in colour, with a large shield-shaped central area of dark brown, with two black dots on it. Forceps with segment 1 broad, as in I. hudsoni McL., but more sharply angulated apically on the inner side; segment 2 very
Fig. 3.—Ventral view of male appendages in the genus Ichthybotus Eaton: a, in I. bicolor n. sp.; b, in I. hudsoni McL. × 14. 1, 2, 3, 4, the four segments of the forceps; 9, 10, the last two abdominal segments; ad, appendix dorsalis; c, cercus (the right cercus is omitted); fb, forceps basis; p, penis.
Fig. 4.—Left lateral view of male appendages in the genus Ichthybotus Eaton: a, in I. bicolor n. sp.; b, in I. hudsoni McL. × 14. Right cercus and right forceps omitted. (For lettering see fig. 3.)
Fig. 5.—Outline of ventral valve in the female of a, Ichthybotus bicolor n. sp., and b, I. hudsoni McL. × 14.
long (but not so long as in I. hudsoni McL.), narrower, and with a row of minute hairs along the basal two-thirds of the inner margin; segments 3–4 very short, subequal. Penis more prominently lobed than in I. hudsoni McL., each lobe carrying a set of minute stiff hairs. Cerci 23 mm. long, dark chocolate-brown, strongly formed, slightly hairy, the segments cylindrical with narrow black basal rings; those of I. hudsoni McL. are quite hairless, yellowish-brown or orange-brown, with broad dark basal rings. Appendix dorsalis vestigial, 1 mm. long, with few segments.
In order that a careful comparison may be made between the appendages of the males of the two species, I have figured them both ventrally in fig. 3, and laterally in fig. 4.
The male may at once be distinguished from that of I. hudsoni McL. by its very dark coloration and its brown hindwings, as well as by the morphological differences given for the appendages.
♀. Subimago: Total length, 16·5 mm.; forewing, 19 mm.; hindwing, 7 mm.; expanse, 40 mm. Generally resembling the same stage in I. hudsoni McL., but with the following differences: The whole body, legs, and appendages are a dull earthy greyish-brown; the forewing has the groundcolour pale-greyish tinged with yellowish, the pale basal patch pale orange, the costal band dull purplish-brown, and the two oblique clouds a medium fuscous and more sharply angulated below R1 than is the case in I. hudsoni McL.; the hindwing is dull purplish-brown, paler towards the base and posterior margin. (In I. hudsoni McL. the hindwing is pale-greyish, with two oblique clouds of medium fuscous.) Ventral valve entire, not bilobed as in I. hudsoni McL. (fig. 5). Cerci 8 mm.; appendix dorsalis 6·5 mm. long.
Types.—Holotype male imago and allotype female subimago in Cawthron Institute collection.
Locality.—Maitai River, Nelson; taken by Mr. A. Philpott on 29th December, 1920. No further specimens have so far been found, but the larva was taken in the following January by Mr. Philpott and myself, by scraping away the loose rubbly bank of the stream. It seems probable that this species may be found widely distributed throughout the South Island if searched for.