Stempellinella Brundin, 1947

Ekrem, Torbjørn, 2007, A taxonomic revision of the genus Stempellinella (Diptera: Chironomidae), Journal of Natural History 41 (21 - 24), pp. 1367-1465 : 1372-1374

Stempellinella Brundin, 1947

Type species: Tanytarsus saltuum Goetghebuer 1921, p 115 . Designated in original description ( Brundin 1947).

Generic diagnosis

Adult male. Small, wing length 0.7–1.7 mm. Body green, yellow, or brown with darker vittae.

Head: antenna with 12 flagellomeres of which only 10 are easily discernible. Antennal ratio 0.5–1.5. Eye ovoid, bare, without dorsomedian extension. Frontal tubercles present as small dots or well-developed cones; 5–12 temporal setae in one row. Mouthparts and apodemes normal.

Thorax: antepronotum widely divided dorsally, bare. Scutum overhanging pronotum, with or without weak scutal tubercle. Acrosticals 8–17; dorsocentrals 5–12; prealars 1–2; scutellars 4–11, humerals 0–3; thorax otherwise bare.

Wing: cuneiform. Membrane and most veins extensively covered with macrotrichiae, denser distally; sub costa, media, and squama bare. Costa not produced; R 4+5 ending opposite or proximal to apex of M 3+4.

Legs: fore tibia with short, slender, apical spur. Combs of mid and hind tibiae narrow, well separated, with one or two spurs. Pulvilli absent or minute.

Hypopygium: anal tergite with transverse or slightly T-shaped anal tergite band. Median tergite setae long anteriorly on tergite or short close to anal point or both. Anal point well developed, slender to broad at base, often narrower and pointed towards apex, with or without well-developed anal crests and anal point spinulae. Some species with groups of microtrichia near anal point base. Setiger of superior volsella oval to almost rectangular, straight to strongly bent medially, with three to six dorsal and two ( Stempellinella truncata three) median setae. Superior volsella otherwise bare. Digitus absent, but contour of superior volsella stem on setiger often prominent. Median volsella with well-developed simple or branched stem with or without microtrichia, lamellae simple blades or setiform. Inferior volsella long, straight or club-shaped with concave median margin, reaching past apex of gonocoxite; with apical setae and microtrichia, dorsal surface otherwise bare. Gonostylus considerably shorter than gonocoxite, often with concave median margin and medially directed apex; median margin with several strong setae, dorsomedian margin usually without microtrichiae.

Adult female. Small, wing length 0.6–1.6 mm. Body green, yellow, or brown with darker vittae.

Head: antenna with five flagellomeres. Antennal ratio 0.2–0.4. Eye ovoid, bare, without dorsomedian extension. Frontal tubercles present as small dots or well-developed cones, usually a bit smaller than in male; temporal setae in one row. Mouthparts and apodemes normal.

Thorax: antepronotum widely divided dorsally, bare. Scutum overhanging pronotum, with or without weak scutal tubercle. Acrosticals 10–18; dorsocentrals 4–8; prealars 1; scutellars 4–7, humerals 0–6; thorax otherwise bare.

Wing: cuneiform. Membrane and most veins extensively covered with macrotrichiae, denser distally; sub costa, media, and squama bare. Costa not produced; R 4+5 ending opposite or proximal to apex of M 3+4.

Legs: fore tibia with short, slender, apical spur. Combs of mid and hind tibiae narrow, well separated, with one or two spurs. Pulvilli absent or minute.

Genitalia: gonocoxapodeme VIII well developed, medially curved. Sternite VIII forms relatively large floor under vagina, covering from one-quarter to more than half of vaginal opening ventrally. Vaginal floor with none to four setae, without suture, margin concave. Gonapophysis VIII simple, rounded lobe with relatively long, densely set, medially directed microtrichia. Labium large, angular. Notum about as long as seminal capsule width, sometimes longer. Rami as long as notum. Seminal capsules ovoid with relatively large, funnel-shaped neck. Spermathecal duct with strong bends, at most slightly longer than rami and notum combined. Tergite IX bluntly triangular or semicircular without shoulders. Gonocoxite IX with one to three setae. Postgenital plate subtriangular. Cercus small to large, approximately as long as seminal capsule width.

Pupa. Small, 1.5–3 mm long. Thorax and lateral margins of posterior abdominal segments brown.

Cephalothorax: frontal setae well developed, taeniate, arising from weakly to strongly developed cephalic tubercles. Frontal apotome smooth to strongly granulose. Frontal warts and pedicel sheath tubercles absent. Thoracic horn elongate with fine to coarse chaetulae. Three taeniate precorneals in slight triangle. Median antepronotal and one lateral antepronotal long, taeniate; other lateral antepronotal seta basiconica. Thorax smooth with few wrinkles to strongly granulose anterodorsally. Prealar tubercle absent to well developed, broad mound. Dorsocentrals simple, in two pairs, anterior pair sometimes slightly stronger. Wing sheath with prominent nose. Pearl row absent.

Abdomen: tergite I bare; II with points in small, round to large triangular patches; III with points in small elongate to large rectangular patches, often p -shaped; IV and V with points in p -shaped patches, occasionally transversely and longitudinally divided; VI with points in four patches or in one p -shaped patch; VII bare, with shagreen in anterolateral patches or with points in transverse anterior patch; VIII with anterolateral patches of shagreen; IX bare or with anterolateral patches of shagreen. Points on tergites II – VI more or less equal in size. Hook row continuous, one-quarter to one-third width of tergite. Pleurae I, II, and VIII bare, pleurae III – VII bare or with shagreen. Pedes spurii A present on segment IV. Pedes spurii B on segment II well developed. Sternites without conspicuous armature. Segment II with 2 D and 3 simple L setae; III with 3 D, 2–3 simple and 0–1 taeniate L setae; IV with 3 D, 2–3 simple and 0–1 taeniate L setae; V with 2–4 D and 3 taeniate L setae; VI with 2–3 D and 3 taeniate L setae; VII with 2–3 D and 4 taeniate L setae; VIII with 1 D and 2–3 taeniate L setae; TIX with 1 D and 8–25 lateral taeniae in anal lobe. Segment VIII with well-developed single spur in posterolateral corner.

Larva. Small, 1.3–3 mm long. Live specimens yellow to pale pink, head capsule brown. Cases straight tubes which are slightly larger in anterior end; case material of fine silt and sand speckled with detritus.

Head: dorsal surface smooth. Clypal seta S3 simple to weakly plumose with three or four branches. Antenna five-segmented, placed on prominent pedestal with welldeveloped spur. Basal segment of antenna 0.7–1.5 × length of segments 2–5. Antennal seta placed basally on segment 1, just above ring organ. Antennal blade well developed, at least reaching antennal segment 2, usually apex of distal Lauterborn organ or beyond. Lauterborn organs large, bulbous, placed alternately on antennal segment 2. Proximal Lauterborn organ on short pedicel near base of segment 3, distal organ on short to moderately long pedicel apically on segment 2. Labral seta SI pectinate, bases fused; SII plumose on tall pedestal; chaetae pectinate to plumose; SIII simple, SIV present. Labral lamella well-developed comb. Pecten epipharyngis consisting of three long, slender, triangular scales. Premandible with two to four teeth, well-developed brush. Premandibular teeth only slightly inclined relative to main axis of premandible. Mandible with pale dorsal tooth; apical and three inner teeth brown. Seta subdentalis long, curved, usually reaching well beyond apical mandibular tooth. Seta interna consisting of four strongly plumose branches. Pecten mandibularis with well-developed lamellae, outer lamella stronger than rest. Mentum with rounded median tooth; six pairs of lateral teeth equal or subequal in size laterad; first pair often more or less fused with median tooth. Ventromental plates fan-shaped with obvious striation, medially at most reaching lateral margin of second lateral tooth. Mentum slightly wider than ventromental plate. Seta submenti placed medially to posteromedian corner of ventromental plate. Postoccipital plate little to moderately developed, continuous or split.

Body: anterior parapods with numerous simple spines; posterior parapods with 12–18 simple claws. Two pairs of conical anal tubules present. Supraanal seta strong and long. Procercus about as long as wide with two short and four long anal setae, short setae set individually and separate from the common base of the long setae.

Comments

The genus morphologically most similar to Stempellinella is probably Zavrelia . However, there are a few characters which can be used to separate the genera in most life stages (Table II). The larvae and pupae of Stempellinella are particularly similar to those of Zavrelia , and combinations of characters are needed to separate Stempellinella and Zavrelia species in these life stages.