Antarctoperlinae Enderlein 1909

Antarctoperlinae gen. sp. IV

(Figs. 36 ‐ 42)

Material examined. 3 LA, Prov. Linares, Catillo, 29 March 1975, CC (in coll. Zwick).

Dimensions. Larva (last instar): body length 9.0; antenna 6.0; cercus 1.5.

Larva. Slender, fully winged, long ‐ legged, larva. Pale matt brown, a narrow sharply delimited median longitudinal line on the abdomen. Antennae very long and slender with a darker ring in basal quarter and another just before mid ‐ length. Subgenual rings on tibiae dark brown. Pilosity not obvious, but very complex and varied at high magnification.

Head not distinctive, dorsally a little concave but depression in front of occipital fork not deep; frons bulging over downwardly directed clypeus and labrum. Eyes large, distinct ocelli. Genae distinct, not as deep as width of antennal scape. Mandibles, maxillae and labium resembling Antarctoperlinae II, but hypopharynx simple, no distinct lobes. Antennae about 2/3 body length, structurally simple, no swollen or conspicuously setose parts, distal segments very thin and several times longer than wide, no distinct setae.

Thorax. Pronotum with all four angles conspicuously horned laterally, the anterior horns curved posteriorly and the posterior ones curved anteriorly. Anterior and posterior margins convex, hind margin with rough short modified hairs. Raised anteromedially part of meso ‐ and metanotum with similar pilosity. Both wing pads divergent, well developed, adult obviously fully winged. Legs simple, long (apex of hind femur reaching to tergite VI), almost hairless, no keels, spines or tibial spurs. Tarsi similar to other Antarctoperlinae, but slender, first segment twice as long as wide.

Abdominal segments ring ‐ shaped, middle and posterior ones strongly constricted medially, with dark spots along bulging distal edge; the setae in these insertion points are very short, club ‐ shaped to almost spatulate with the wide apices pale and transparent. Interspersed with the setae are a few long thin twisted or curled pale hairs which are best seen in slanting light and then give the larva an untidy appearance. On the tergal surfaces, in transmitted light, between the few pale club ‐ shaped setae are numerous minute thinly stalked floriform chloride cells which have only a few delicate cuticular rods surrounding the central vesicle (normally, there is a dense basket ‐ like arrangement of cuticular rods around it). Segment 10 with its distal dorsal edge regularly rounded and fringed with short setae, its ventro ‐ distal face covered by elongate triangular, prominently pointed, sclerotised subanal lobes. In side view, the ventral edge of the subanal lobe forms a straight line, from base to tip. Cerci directed postero ‐ laterally. They are basally light brown, regularly segmented and sparsely pilose but distally completely pale, indistinctly segmented and hairless. Gill rosette large, purplish.

Remarks. The male larva is insufficiently developed to show distinct secondary sexual characters, except for an indistinctly bilobed slight mediodistal extension of sternite 9. The dark dorsal line is most distinct and longest in the smallest larvae, but least developed in the largest specimen. However, this may be related to the condition of the specimens rather than being typical of given instars. By the shape of their wing pads, the three available larvae belong to the last three instars; their body proportions suggest wing development is in three steps, as in most Plecoptera (Zwick 2003).

Slender shape and pronotal angles suggest this may be the larva of some Plegoperla species. However adult Plegoperla have forwardly directed anterior angles of pronotum and the short extension of the posterior angles is directed backward. Also, Plegoperla adults have very long antennal scapes and tibial spurs which are lacking in the Antarctoperlinae IV larva.