Acostatrichia simulans Mosely, 1939

Angrisano, Elisa B. & Sganga, Julieta V., 2010, Preimaginal stages of Acostatrichia simulans Mosely 1939, a Neotropical microcaddisfly (Trichoptera: Hydroptilidae: Leucotrichiinae), Zootaxa 2480, pp. 54-60 : 56-59

Acostatrichia simulans Mosely, 1939

Figs. 1–18

Larva. Length of body: up to 3 mm. General coloration of body white and green, with grayish brown sclerites ( Figs. 14–15 ).

Head. Subquadrangular in dorsal view, slightly rounded laterally and posteriorly; pilosity reduced; coronal suture well defined, branches of frontoclypeal suture lightly insinuated; frontoclypeus bearing reticulate sculpturing, without papillae; tentorial pits well defined; antennae short; labrum cleft mesally, with row of 4 long, mesal setae, and shorter setae especially on inner side; mandibles subtriangular, robust, with lightly defined teeth, almost blunt ( Fig. 1 ).

Thorax. Pronotum subquadrangular, anterior margin almost straight, posterior margin more heavily sclerotized and pigmented than rest of tergum, slightly produced mesally and with deep, U-shaped indentation, lateroposterior corners rounded; mid-dorsal ecdysial line present; with setae distributed along anterior and lateral margins, and approximately 7 to 8 setae in middle of each pronotal plate ( Fig. 2 ). Meso- and metanota without ecdysial lines. Mesonotum quadrangular, narrower and more heavily sclerotized posteriorly, bearing 4 to 5 long setae anteriorly, and shorter setae mesally ( Fig. 3 ). Metanotum narrower than pro- and mesonota; with short setae distributed anterior and mesally, except for a long seta on each anterolateral corner, of same length as sclerite; posterior and centre of anterior margins heavily pigmented, with strongly pigmented area, not clearly defined, between metanotum and abdominal segment I ( Fig. 4 ). Mesothorax with small subtriangular posteroventral plate. Thoracic tergites superimposed at rest, separated by wide, membranous areas allowing extension of segments, providing great mobility to larvae. Legs short, broad, without any particular modification; chaetotaxy reduced; tarsal claws short, each with wide, curved basal seta ( Fig. 5 ). Pro-, meso-, and metathoracic legs similar to each other except metathoracic legs with coxa longer than others.

Abdomen. All segments with central tergite; segments I to VIII each with circular, pleural sclerite bearing 2 to 3 setae. Abdominal segment I shorter and narrower than the others; its central tergite rectangular, wide, almost entirely covering dorsum, 4 times wider than long; anterior and posterior margins slightly curved forward; bearing pair of long lateroanterior setae, 3 pairs of lateral ones, and mesolateral pair of sensory pits ( Fig. 6 ) (there is a pair of these pits on each of segments I–VIII). Segment II with tergite wide and short, convex posteriorly and almost straight anteriorly; with pair of mesal pores (present on each of segments II– VII), and chaetotaxy similar to that of tergite I ( Fig. 7 ). Segments III to VII with central tergite gradually narrower and longer than that of segment I, with that of segment VII almost subtriangular; each tergite with 3 to 4 pairs of lateral setae; each of these segments with additional pair of lateroanterior, circular tergites, each bearing 1-2 setae ( Figs. 8–9 ). Tergite of segment VIII subrectangular, rounded lateroposteriorly; with pair of long, lateroposterior setae, and 6 pairs of shorter, lateral setae and rigid spines; without sensory pits ( Fig. 10 ).

Tergite of segment IX longer than wide, quadrangular, anterior margin lightly excavated mesally and posterior end rounded; bearing approximately 32–34 stout setae, 3 pairs of long lateroposterior setae, longer than segment, and very small spines along posterior margin ( Fig. 11 ). Anal prolegs lengthened, claws deeply arched, each without accessory claw ( Fig. 12 ); membranous area between legs with microtrichiae.

Larval case. Length 3 mm; width 2 mm. Oval, typical of Leuchotrichiinae, irregular, open ventrally and at both ends; anterior and posterior openings with flanges (bottle neck-like) ( Figs. 16-18 ).

Pupa. Mandibles without teeth. With dorsal anterior hook plates on segments III–VII, and posterior ones on segments III–V; plates small, circular, with 10 to 13 small hooks of same size ( Fig. 13 ).

Pupal case. Completely closed; ventrally with a floor of thin silk, thinner than dorsal sheet ( Fig. 16–17 ). Emergence occurring through large, anterior, subcircular opening.

Material examined. Argentina: Misiones Province: Salto Encantado Provincial Park, Arroyo Azul, 23- 28.i.2008, Angrisano & Sganga leg., 6 larvae, 10 metamorphotype males, numerous larval and pupal cases.

Biology and habitat. Larvae and pupae were attached to rocky substrate in riffles and pools of the Arroyo Azul, a 1st order tributary of the Arroyo Garuhapé. They were found in a sunny section of the stream where the canopy was partially open. In this section the stream is 5–6 m wide, with clean, warm water (22 ºC, pH =7, conductivity= 210μS.cm -1), ranging from 1 to 35 cm in depth. The rocks had a great number of cases that were situated separately (in Abtrichia antennata they are usually found in pairs); the cases were more abundant in shallow areas of the reach.

Figures

FIGURES 1 – 13. Acostatrichia simulans. Larva. (1) Cephalic capsule, dorsal. (2) Pronotum. (3) Mesonotum. (4) Metanotum. (5) Right prothoracic leg, external. (6) Abdominal tergite I. (7) Abdominal tergite II. (8) Abdominal tergite III. (9) Abdominal tergite VII. (10) Abdominal tergite VIII. (11) Abdominal tergite IX. (12) Right anal proleg (and membranous area between the prolegs), right lateral. Pupa. (13) Dorsal abdominal plates, IVp: right posterior plate IV, Va: right anterior plate V.

FIGURES 14 – 18. Acostatrichia simulans. (14, 15) Larva, right lateral. (16) Pupa in the pupal case, ventral. (17) Cases attached to a rock, dorsal, lc: larval case, pc: pupal case. (18) Detail of the opening of the larval case, left dorsal oblique.