Agapetus episkopi Malicky 1972

Karaouzas, Ioannis, 2017, The larva of Agapetus episkopi Malicky 1972 (Trichoptera: Glossosomatidae), including a key to the larvae of Glossosomatidae of the Hellenic western Balkan region, Zootaxa 4329 (1), pp. 73-80 : 74-79

Description of the final instar larva of Agapetus episkopi Malicky 1972

Biometry. Body length ranging from 3.2 to 3.9 mm, head width from 0.37 to 0.40 mm (n = 8).

Head. Head capsule elongated, medium to chestnut brown, with smooth surface ( Figs. 1–3 ). In lateral view, head profile slightly flattened ( Fig. 2 ). White ring around each eye ( Figs. 1–2 ). Head capsule with complete set of 18 pairs of primary setae: 10 dorsal and 2 ventral primary setae on each parietal, 6 pairs of primary setae on frontoclypeus. Antennae originating near anterior parietal margin. Labrum brown, with black proximolateral margins and terminal membraneous fringe; with 3 pairs of primary setae. As in other Agapetinae ( Wiggins 1996) , ventromesal margins of parietalia not thickened, and length of median ventral ecdysial line ( Fig. 3 el) 1.5–1.6 times longer than each divergent anterior branch enclosing submentum ( Fig. 3b ). Submentum narrow, V-shaped ( Fig. 3 ); submental sclerites separated ( Fig. 3 sc).

Mandibles asymmetrical, with left mandible nearly right triangle and right mandible nearly equilateral triangle; yellowish-brown, of scraper-type, lacking terminal teeth along edges as well as lacking ridges in central concavity. Each mandible with one long basodorsal seta and group of 5 shorter, flexible ventral setae. Unworn mandibles each with large, rounded tip, subterminal crenulated scraping edge ventrally, and subterminal smooth edge dorsally ( Fig. 3A ). Concavity of each mandible with group of pinnate setae ( Fig. 3A ). In strongly worn mandibles, tips and scraping edges nearly smooth ( Fig. 3B ).

Thorax. Pronotum medium brown, with dark brown muscle attachment spots (muscle scars of Wiggins 1996), two heavily sclerotized, smooth plates meeting mesially along narrow, straight suture. With brown spot (not seen in Fig. 4p due to steep viewing angle) and 8–10 setae above each foreleg insertion ( Fig. 4p ). Anterolateral setal group consisting of 23–26 black setae of varying lengths, posterolateral and posteromedian setal groups consisting of 5–7 setae each. Mesonotum with 2 medium brown, lightly sclerotized, trapezoidal sclerites tapering posteriorly and covering approximately half of the mesonotal surface ( Fig. 4s ). Setation consisting of 1 anteromedian, 1 posteromedian, and 1 lateral paired setae (sa 1, sa 2, and sa 3, respectively, of Wiggins 1996). Metanotum bearing pair of small, lightly sclerotized, ovoid, medium brown sclerites between anteromedian and lateral setae ( Fig. 4t ). Setation same as on mesonotum. Legs light brown, of approximately the same size ( Figs. 5–7 ). Ventral edge of each femur with 1 strong pale, yellowish seta at mid-length about half as long as 1 slender black apical seta; subapically, each tibia with set of 2 short, pale lateral spines and 1 central spatulate spine. Tarsal claws curved, each with basal seta originating from tiny base ( Figs. 5–7 ). Prosternal sclerites large, wedge-shaped, medium brown with dark anterior borders and pale lateral and posterior borders ( Fig. 8 ps); mesosternal sclerites much smaller, transverse, narrow, and elongate ( Fig. 8 ms). Metasternal sclerites absent.

Abdomen. Abdominal segments I–VIII without sclerites. As typical for “Spicipalpia”, abdominal segment I without fleshy protuberances. Sternum II with pair of patches of microscopic spines ( Fig. 9 ) as described by Craft & Morse (1997). Dorsal setation of abdominal segments consisting of 3 pairs of setae: anteromedian, posteromedian, and lateral paired setae (sa 1, sa 2, and sa 3, respectively, of Wiggins 1996), with 1 anteromedian and 1 posteromedian setal pair on each of terga I–VIII, 2 pairs of lateral setae on terga I and VIII, 1 pair of lateral setae on tergum II and 2 pairs of tiny pale setae medially of each median lateral seta on tergum VIII ( Fig. 12 ss). Each abdominal segment with 1 pair of ventrolateral setae except on segments VI and VII ( Figs. 9 vs, 10vs). Gills and lateral fringe lacking. Dorsal sclerite of abdominal segment IX medium brown, trapezoidal, its crenulate posterior margin with 8 setae of almost equal length, including pair of outermost setae ( Fig. 12 , arrow); pair of smaller setae also present. Proximal sections of anal prolegs broadly joined with segment IX, their lateral sclerites medium brown, rectangular, each with 4 long, black apicodorsal setae (1 seta broken in Fig. 11 ); distal section free from abdomen, leg-like, ventral sole plate ( Wiggins 1996) light brown ( Fig. 11 ). Anal claws dark brown, each with 2 tiny dorsal accessory hooks ( Figs. 10, 11 ). As typical for Agapetinae ( Wiggins 1996) , anal opening without pair of vertical sclerotized bars along each side ( Fig. 11 ), but with anal papillae ( Fig. 11 ap).

Larval case. Tortoise-shaped, with flat ventral transverse strap (‘plastron’ sensu Wiggins 1996) and convex dorsal outline, 4.5 to 5.5 mm long, 1.9 to 3.6 mm wide, and 1.4 to 1.8 mm high (n = 8). Ventrally, with two openings near anterior and posterior border which can be shut by hinged closures consisting of mineral particles and silk ( Fig. 13 ). Cases made of mineral particles of mixed size ( Figs. 13–15 ).

Morphological diagnosis of fifth instar larvae of Agapetus episkopi Malicky 1972 from those of other

European Trichoptera

A summary of morphological features for the identification of European caddisfly families was given by Waringer & Graf (2013). Within the framework of the key for larvae of Trichoptera families by Pitsch (1993) and Waringer & Graf (2011), glossosomatid larvae are separable from those of other families by possessing the following features: - with transportable case shaped like a turtle shell ( Figs. 13 , 20 ); - labrum sclerotized ( Fig. 1 );

- tergite IX sclerotized ( Fig. 12 );

- abdominal segment I without fleshy protuberances ( Fig. 9 ); - prosternal horn absent.

In the context of the Glossosomatid larvae of European Ecoregion 6 (Hellenic western Balkan region), Agapetus episkopi belongs to subfamily Agapetinae where the pronotum is completely sclerotized and covered by two plates in close median contact ( Fig. 4p ); meso- and metanota are incompletely sclerotized and each bearing only two small sclerites ( Figs. 4s, 4t ). Within Agapetinae , the dorsal case profile is rounded in A. episkopi , and a sand collar is not attached to its base ( Figs. 14, 15 ), as it is common in genus Synagapetus ( Fig. 20 ). Therefore, A. episkopi keys together with Agapetus laniger and A. delicatulus , and can easily be separated from the latter two because A. episkopi ( Figs. 1, 2 ) lacks the pale area on the frontoclypeus of those species and the pale posterior sections of the parietalia of A. laniger (Fig. 21).

Key to the hitherto known final instar Agapetus larvae of European Ecoregion 6

(Hellenic western Balkan)

1 Pronotum fully sclerotized, meso- and metanota completely membranous ( Fig. 16p ).................................2

- Dorsal sclerites present on all three thorax nota ( Fig. 4p, 4s, 4t ).................................................3

2 Lateral pair of setae (setae 1a of Waringer & Graf 2011) on dorsal sclerite of abdominal tergum IX originating at posterior margin and almost as long as other setae along posterior margin of this sclerite ( Fig. 17 , arrow) ................................................................................................... Glossosoma conforme Neboiss 1963

- Lateral pair of setae on dorsal sclerite of abdominal segment IX distinctly set anterior of posterior margin and significantly shorter than other setae along posterior margin of this sclerite ( Fig. 18 , arrow)....... Glossosoma bifidum McLachlan 1879

3 With one lateral seta on each side of abdominal tergum III ( Fig. 19 ls); case with sand collars ( Fig. 20 )...................................................................................... Synagapetus iridipennis McLachlan 1879

- Without lateral setae on abdominal tergum III ( Fig. 9 ); case without sand collars ( Fig. 13 )............................ 4

4 With two lateral setae (ls) on each side of abdominal tergum I ( Fig. 9 ls); frontoclypeus without pale central area ( Fig. 1 ).............................................................................. Agapetus episkopi Malicky 1972

- With one lateral seta (ls) on each side of abdominal tergum I ( Fig. 19 ); frontoclypeus with pale central area (Fig. 21a)...... 5

5 Posterior sections of parietalia with pale areas (Fig. 21b); lateral setae on abdominal tergite IX almost as long as other setae along posterior margin of this sclerite (as in Fig. 12 , arrow).............................. Agapetus laniger Pictet 1834

- Posterior sections of parietalia without pale areas; lateral setae on abdominal tergite IX distinctly shorter than other setae along posterior margin of this sclerite (as in Fig. 18 , arrow).......................... Agapetus delicatulus McLachlan 1884

Ecology and distribution. Agapetus episkopi is found on most islands of the Aegean Sea, including Crete, Euboea, Andros, Tinos, Kea, Naxos, Ikaria, Skiathos, Skopelos, Chios, and Samos ( Malicky 2005b, 2014). There are only two records from the coast of the mainland: Monemvasia (southern Peloponnese) and Platamonas (northern Greece). The species is also widespread in the western part of Turkey ( Sipahiler 2008).

Larvae of Agapetus episkopi inhabit a wide range of stream habitats from slow to moderate currents and low to medium water temperatures. Altitudinal distribution ranges from 0 to 650 m a.s.l., and their microhabitats are composed of cobble, pebbles, gravel, and abundant coarse particulate organic matter. Glossosomatid larvae are specialised for feeding on the uppermost exposed rock surfaces ( Wiggins 1996), and in fact can often be observed on mineral surfaces above water and covered only by a very thin film of drizzle (hygropetric habitats). With their scraper-type mandibles ( Figs. 3A, 3B ) and the membranous labrum fringe, they graze on biofilm, cyanobacteria, diatoms, green algae, and associated fine organic particles. Another interesting feature in this family is the fact that the distal halves of the anal prolegs are free from the abdomen ( Fig. 11 ), permitting the larva to extend them through the case opening for stabilizing the case on the external substrate ( Wiggins 1996).

In Crete, adults can be found all year round with four emergence maxima, the highest being in May–June and September–October ( Malicky 2005b). On Serifos, A. episkopi is on the wing during May–June, although a longer flight activity is expected. Agapetus episkopi is sympatric with Hydroptila aegyptia Ulmer 1963 , H. kalonichtis Malicky 1972 , H. vectis Curtis 1834 , Oxyethira falcata Morton 1893 , Hydropsyche pygmalion Malicky 2001 , Polycentropus ierapetra Malicky 1972 , Tinodes horstaspoecki Malicky 1975 (in Kumanski & Malicky 1975), T. serifos Malicky 1984 , and Wormaldia subnigra McLachlan 1865 .

Figures

FIGURE 20. Glossosomatidae genn. spp., final instar larvae. 20, Synagapetus iridipennis McLachlan 1879, larval case, ventral (arrows = collar of sand grains). 21, Agapetus laniger Pictet 1834, head, frontal (a = pale central patch on frontoclypeus, b = pale patches on posterior sections of parietalia). Scale bars: 0.5 mm.

FIGURES 1 – 6. Agapetus episkopi Malicky 1972, final instar larva. 1, head, dorsal; 2, head, dorsolateral; 3, head, ventral (b = anterior branch of ventral ecdysial line, el = ventral ecdysial line, sc = submental sclerite); 3 A, unworn left mandible, ventral; 3 B, strongly worn right mandible, ventral; 4, thorax, dorsal (p = pronotal sclerite, s = mesonotal sclerite, t = metanotal sclerite); 5, left foreleg, posterior face; 6, left midleg, posterior face. Scale bars: 0.5 mm (except Figs. 3 A, 3 B: 0.1 mm).

FIGURES 7 – 13. Agapetus episkopi Malicky 1972, final instar larva. 7, left hind leg, posterior face; 8, thorax, ventral (ms = mesosternal sclerite, ps = prosternal sclerite); 9, metathorax and abdominal segments I – IV, right ventrolateral (ls = lateral seta, vs = ventral seta); 10, abdominal segments IV – IX, right lateral (vs = ventral seta); 11, posterior tip of abdomen, right posterolateral (ap = anal papillae). 12, posterior tip of abdomen, dorsal (arrow = left posterolateral seta on tergite IX; ss = alveolae of tiny pair of pale setae); 13, larval case, ventral. Scale bars: 0.5 mm.

FIGURES 14 – 19. Glossosomatidae genn. spp., final instar larvae. 14 – 15, Agapetus episkopi Malicky 1972: 14, larval case, dorsal; 15, larval case, lateral. 16 – 17. Glossosoma conforme Neboiss 1963: 16, thorax, dorsal (p = pronotum); 17, posterior tip of abdomen, right lateral (arrow = left lateral seta on abdominal tergite IX). 18, Glossosoma bifidum McLachlan 1879, posterior tip of abdomen, right lateral (arrow = left lateral seta on abdominal tergite IX). 19, Synagapetus iridipennis McLachlan 1879, abdominal segments I – IV, right lateral (ls = lateral seta). Scale bars: 0.5 mm.