Drusus ramae, Marinkovic-Gospodnetic, 1971

Posilović, Hrvoje, 2010, Description of the larvae of Drusus ramae Marinković- Gospodnetić and Drusus medianus Marinković- Gospodnetić (Trichoptera: Limnephilidae) with some genetic, distributional, ecological, faunal and conservation notes, Zootaxa 2484, pp. 1-24 : 5-8

Description of the fifth instar larva of Drusus ramae

Case and Larva

Case constructed of mineral particles and in some specimens from gastropod cases ( Fig. 1 ), slightly curving, total length 11.20–15.49 mm (n=20), width of anterior part 3.21–3.60 mm, width of posterior part 1.59–2.49 mm. Overall body shape eruciform ( Fig. 2 ), total length without case 11.22–13.49 mm (n=20).

Head

Head capsule hypognathous, flat in vertex (posterior part of head) ( Figs 1–5 , 7 ), with width 1.45–1.71 mm (n = 20). Head brown and dark brown to black, dorsally darker and laterally lighter ( Fig. 3 ), with granular surface sculpturing ( Fig. 4 ). Genae of the parietals reddish-brown to yellow with lighter (yellow) ring around each eye ( Fig. 3 ). Posterior part of dorsum with numerous, dark muscle attachment spots. Frontoclypeal apoptome bell-shaped with narrow central region ( Fig. 5 ). Antennae short, brown to dark brown, each positioned on small, noticeable prominences, accompanied by 2 prominent lateral seta (setae no. 7 and no. 9) ( Fig. 5 ). Other primary setae positioned as shown in Fig. 5 . Setae no. 1, 4, 6, 10, and 11 light, inconspicuous; setae no. 8, 12 and 13 dark, inconspicuous; setae no. 2, 3, 5, 7, 9, 14, 15, 16, and 17 dark, prominent. Setae no. 1, 2, 3, 4, 5, 7, 9, 14, 15, 16, and 17 long; setae no. 6, 8, 10, 11, 12, and 13 short.

Labrum symmetrical, brown to yellowish (anterior apart), with setal brush at anterolateral margins and 5 pairs of thin primary setae on dorsal surface.

Mandibles black, mesal part reddish. Typical for grazers, mesal margin with setal brush and without teeth, although usually each mandible with minor irregular mesal margin in front of setal brush ( Fig. 6 ). Two setae present laterobasally on each mandibles ( Fig. 6 ).

Labium and maxillae light-brown (yellowish). Maxillary palps 5-segmented.

Thorax

Pronotum brown to black with granular surface sculpturing ( Figs. 3–4 ). Posterior margin rounded, both posterior and lateral margins thick and darkly sclerotized ( Fig. 3 ). Anterior half of pronotum convex, posterior half forming pairs of prominent acute humps ( Figs 3–4 , 9 ), separated by distinct indentation. Pronotum bearing dark setae, especially laterally and on anterior margin, some of them long and conspicuous ( Figs 3–4 , 7–8 ). Dorsal and lateral regions of pronotum bearing short, white, recumbent setae, with some specimens bearing only small number of these. Prosternal horn present.

Mesonotum sclerites brown, lighter than pronotum, with dark muscle attachment spots and uneven (rugged) surface. Numerous dark setae at positions sa 1, sa 2 and sa 3 ( Fig. 9 ). Posterior and lateral margins thick and darkly sclerotized.

Metanotum with 3 pairs of dorsal sclerites ( Fig. 9 ). Anteriormedian (sa 1) sclerites triangular, with distance between them shorter than their length ( Figs 9 , 46–47 ) ( Tab. 2), covered by setae, mainly anteromedially, colour similar to mesonotum. Posteriormedian (sa 2) sclerites smaller and lighter than sa 1 sclerites ( Fig. 9 , 46–47 ), transversely and irregularly elongated and with dark setae. Groups of setae present on membranes between sa 2 sclerties and between sa 2 and sa 3 sclerite. Lateral sa 3 sclerites longitudinally prolonged, sickle-shaped, lighter brown with dark median region, and group of setae anteriorly ( Fig. 9 ).

Legs yellow-brown to brown or black, with dark ventral and dorsal margins ( Figs 1–3 ). Foreleg coxae with dark setae on ventral and dorsal edges. Foreleg trochanters without dorsal setae, each with few lightyellow setae on ventral margin and distally with dense row of short, fine, yellowish setae (trochanteral brush) continuing onto basoventral margin of femur ( Fig. 10 ). Foreleg femora each with dark setae on dorsal edge, a few stout, light-yellow setae on ventral margin in addition to basoventral dense row of short, fine, yellowish setae ( Fig. 10 ). Mid- and hind leg coxae and femora with dark setae on both ventral and dorsal edges, midleg trochanters with few, fine, yellowish setae apicoventrally ( Figs 11–12 ). Additional setae present on anterior and posterior faces of all femora. Setae on dorsal edges of tibiae present only distally in all legs. Tarsae each with claw light brown to reddish-brown, tarsal basal seta and tibial spurs lighter yellowish. Foreleg coxae and femora wide compared to those of mid- and hind legs ( Figs 10–12 ). Mid- and hind-legs similar in shape and size ( Figs 11–12 ), with slender coxae, trochanters, femora and tibiae.

Abdomen

Abdominal segment I with well-developed dorsal and lateral humps (protuberances). Numerous setae present anterior and lateral to dorsal hump. It is not possible to distinguish between setal areas sa 1 and sa 2 on dorsal side. With numerous ventral setae, some of them with small sclerites at bases. Lateral humps with few setae.

Single filamentous gills ( Fig. 2 ) present on segments II–VII ( Fig. 13 ). Dorsal pre-segmental gills present on segments II–VII and dorsal post-segmental gills present on segments II–VI. Lateral pre-segmental gills presents on segments III–IV and lateral post-segmental gills on segments II–V. Ventral pre- and postsegmental gills present on segments II–VII ( Fig. 13 ). In some specimens, dorsal post-segmental gills on segment VI, pre-segmental gills on segments VII, and lateral post-segmental gills on segment V are not always present ( Fig. 13 ). Dorsal setae on abdominal segment VIII vary in number from 0 to 6. In only 7 % of specimens 0 or 3 setae were recorded. Lateral fringe extending from last third of segment II to first half of segment VIII (sometimes few setae in second half); in some specimens, only few setae forming lateral fringe on segment II.

Segment IX bearing irregular, semicircular, light brown dorsal sclerite, with 8 long dark setae on posterior margin and several shorter, lighter setae on posterior half of sclerite ( Fig. 14 ). Anal prolegs typical of limnephilids ( Fig. 15 ), each with lateral sclerite longitudinally prolonged, sickle-shaped, yellowish with small setae scattered over posterior 2/3rds and 2 large, dark setae at posterior end ( Fig. 15 ). Anal claws brown.

Figures

FIGURES 1 – 6. Drusus ramae Marinković- Gospodnetić, 1971. 1, larva in its case, right lateral view; 2, larva, right lateral view; 3, head and pronotum, right lateral view; 4, head and pronotum, left dorsolateral view; 5, head, frontal view; 6, right mandible, dorsal view.

FIGURES 7 – 12. Drusus ramae Marinković- Gospodnetić, 1971. 7, pronotum left lateral view; 8, pronotum, right lateral view; 9, thorax (pronotum, mesonotum and metanotum), dorsal view; 10, right foreleg, lateral view; 11, right mid-leg, lateral view; 12, hind-leg, lateral view.

FIGURES 46 – 53. Metanota of Drusus spp., showing anteromedian (sa 1) and posteromedian (sa 2) sclerites. 46 – 47, Drusus ramae Marinković- Gospodnetić, 1976; 48 – 49, Drusus medianus Marinković- Gospodnetić, 1971; 50 – 51, D. radovanovici septentrionis Marinković- Gospodnetić, 1976; 52 – 53, Drusus croaticus Marinković- Gospodnetić, 1971.

FIGURES 13 – 15. Drusus ramae Marinković- Gospodnetić, 1971. 13, gill diagram: position of filaments on left side of abdominal segments I – VIII; ●, gills always present; O, gills not always present; 14, abdominal segment IX, dorsal view; 15, anal proleg, left lateral view.