Chimarra minima, Ulmer, 1907

Gibon, François-Marie, 2015, The Chimarra minima group in West Africa and Madagascar (Trichoptera, Philopotamidae), Zoosystema 37 (2), pp. 333-350 : 334-335

The Chimarra minima group

PRELIMINARY REMARK

Except for the neotropical region, which has benefited from the studies of Blahnik (1997, 1998 and 2002), the evolutionary history of the genus Chimarra is still poorly known and based on the conclusions of Ross (1956). At that time, less than a quarter of the species known today were described and the history of the genus is probably longer and more complicated than Ross proposed. However, he was already able to characterize some major lineages mostly based on structures of the tergum X. In the most primitive forms, tergum X is entire and sclerotized. The following evolutionary steps included the splitting of this tergum into one mesal and two lateral lobes and the transformation of the dorsal lobe, which becomes membranous and subsequently disappears.

DIAGNOSIS. — In the C. minima group, the mesal lobe of tergum X has disappeared, the lateral lobes are widely separated and split into two secondary lobes. Furthermore, tergum IX is membranous dorsally: when viewed caudally, the ninth segment is not ring-shaped but U-shaped or horseshoe-shaped ( Fig. 1 ). These characters suggest that the C. minima group might be a relative of the C. tsudai group. The latter was erected by Ross (1956), who hypothesized that C. tsudai Ross, 1956 was close to the “asiatic ancestor” that initiated one of the colonization movements from Asia to Africa. It was formally described by Blahnik et al. (2009), who listed 130 species from Japan to Pakistan (subsequently, Blahnik et al. (2012) described five more species from Vietnam). In the C. tsudai group, the lateral lobes of tergum X are secondarily subdivided into sclerotized lateral and mesal lobes, and the lateral lobes, and sometimes the mesal lobes, bear numerous sensilla. In the C. minima group, the lateral lobes of tergum X are secondarily subdivided into sclerotized dorsal and ventral lobes (subsequently referred to as latero-dorsal and latero-ventral lobes), and the dorsal lobes usually have two sensilla. Moreover, the long inward deformation of the dorso-distal angle of the inferior appendages and the phallotheca ending in two long, lateral and spear-shaped processes are characteristic of the C. minima group. Finally, in the C. tsudai- group, both veins 2A and 3A of the forewing are looped to 1A, in the C. minima group, 2A appears to be Y-shaped apically ( Fig. 2 ).

DESCRIPTION

Adults yellow or pale yellow, wings without patch or pattern. Ocelli 3. Labial palps 3-segmented. Maxillary palps 5-segmented. Spur formula 1/4/4. Forewing ( Fig. 2 ): Rs sinuous, with node before discoidal cell, R1 and stem of M1+2 slightly sinuous; forks 1 and 2 present, sessile; fork 3 present, petiolate; fork 4 absent; fork 5 present; extremity of Cu2 curved and joining wing margin a little beyond 1A; sc-r, r, s, r-m, m, m-cu and cu present. Hindwing ( Fig. 2 ): R1 apparently fused to subcosta, forks 1 and 2 present, sessile; fork 3 present, petiolate; fork 4 absent; fork 5 present; 2A looped to 1A.

Abdominal segment IX distinctly produced anteroventrally, with short posteroventral process, dorsally membranous (U-shaped when viewed caudally). Preanal appendages, short, simple. Inferior appendages bulky, almost rectangular or trapezoidal in lateral view and C-shaped in caudal view; heavily sclerotized, with inward directed elongation of the dorso-distal edge and spine-shaped protuberance or small bump on the inner side. Mesal lobe of tergum X absent. Lateral lobes distally split, over most of their length. Laterodorsal lobes highly sclerotized, rod, sickle or hook-shaped; latero-ventral rod, plate or sheet-shaped, sometimes absent. Phallotheca tubular, arising from bulbous base, ending in two long, lateral, pointed rods. Endotheca with phallotremal sclerite and one short internal spine, absent in some species.

REMARKS

Two subgroups and two isolated species may be distinguished, based on the shape of the latero-ventral lobes of tergum X. In most species, this latero-ventral lobe forms a lateral sheet or a plate along the phallus apparatus (subgroup 1). This plate is sometimes thin, membranous and, for this reason, not visible after clearing in KOH; it is consequently missing from the original descriptions, at least in the case of C. ambaja Mosely, 1939 , C. callasae Gibon, 1982 , C. sassandrae Gibon, 1982 and C. toubaensis Gibon, 1985 . I give new figures (lateral view) for the male genitalia of these species ( Figs 3E, F ; 5G ). In some species, the latero-ventral lobe is, like the latero-dorsal lobe, heavily sclerotized, branch or sword-shaped (subgroup 2). In C. minima , the latero-ventral lobe is an elongated and narrow plate with a more strongly sclerotized spiny distal thickening. In C. intexta Mosely, 1931 , the latero-ventral lobe is absent.

Table 1. — Preliminary List Of The Chimarra minima Group

Figures

FIG. 1. — Chimarra antsymeloka n. sp., abdominal segments VIII, IX and X (without inferior appendages and phallic apparatus), caudal view. Abbreviations: ldl, latero-dorsal lobe; lvl, latero-ventral lobe; s, segment; t, tergum; vp, ventral process. Scale bar: 0.1 mm

FIG. 2. — A-C, wings: A, Chimarra vulgaris n. sp.; B, Chimarra antsymeloka n. sp.; C, Chimarra assambae n. sp. Scale bar: 1 mm. Abbreviations: A, anal vein; Cu, cubitus; M, medius; R, radius; Sc, subcosta.

FIG. 3. — A, B, Chimarra callasae Gibon,1982:A, segments IX and X,lateral view; B, phallic apparatus,lateral view;C, D, Chimarra minima Ulmer, 1907, holotype male: C, segments IX and X, lateral view; D, phallic apparatus, lateral view; E, Chimarra sassandrae Gibon, 1982, segments IX and X, lateral view; F, Chimarra toubaensis Gibon, 1985, segments IX and X, lateral view. Scale bar: 0.1 mm.

FIG. 5. — A-F, Chimarra antsymeloka n. sp.: A, inferior appendage, dorsal view; B, segments IX and X, lateral view; C, tergum X, dorsal view; D, Chimarra antsymeloka n. sp., specimen from the Efaho River (near Ifarantsa), tergum X, dorsal view; E, Chimarra antsymeloka n. sp., specimen from the Menarandra River (near Tranoroa), tergum X, dorsal view; F, phallic apparatus, lateral view; G, Chimarra ambaja Mosely, 1939, segments IX and X, lateral view. Scale bar: 0.1 mm.