Description of the final instar larva of Silo chrisiammos Malicky 1984

Biometry. Body length ranging from 6.7 to 8.6 mm, head width from 0.86 to 1.00 mm (n = 3).

Head. Head capsule roundish, with strongly protruding eyes and orange to reddish brown coloration; surface coarsely granulated (Figs. 1–3). In lateral view, head profile rounded (Fig. 3). Pale ring around each eye (Fig. 3). Head capsule with complete set of 18 pairs of primary setae and small number of tiny pale secondary setae in occipital region. On each parietal, 10 dorsal and 2 ventral primary setae present, frontoclypeus with 6 pairs of primary setae. Antennae originating within small dents halfway between anterior eye margin and anterior head capsule margin (Fig. 1, arrow), each consisting of 1 short cylindrical base and 1 short flagellum. Labrum brown, with 3 pairs of primary setae at anterolateral corners; anteriorly, with 1 small median and 2 large lateral lobes, the latter fitted with long setal brushes (Fig. 2). Ventral apotome very narrow and elongate, amphora-shaped, orange, postgenal suture approximately 39% of apotome length; horn-like, curved anterolateral lobes present (Fig. 4). Mandibles black, lacking terminal teeth along edges as well as lacking ridges in central concavity (Fig. 4).

Thorax. Pronotum enlarged, coarsely granulated, with lateral yellowish-brown semicircular and plate-like extensions (Fig. 5); the latter extended anterolaterally, pointed, and partially divided by short oblique transverse suture at two-thirds distance from anterolateral angle (Fig. 5 s). Central pronotal section medium to dark brown, fitted with single, nose-like dorsal hump widest along anterior pronotal border and fading in height and width when approaching the posterior pronotal border (Figs. 5 n, 6n), thereby creating two dark brown lateral dents (Figs. 5 d, 6d). In anterior view, anterior pronotal border steeply sloped dorsally, shaping a semicircular retraction space for the head capsule (Fig. 1). Pronotal muscle attachment spots dark brown, each lacking border of dark-pigmented dots present in other Goeridae larvae.

Mesonotal sclerites coarsely granulated, medium brown, arranged in 3 closely-fitting pairs with suture clearly visible between sclerites arbitrarily numbered 1 and 2 (Fig. 7). With dorsal transverse hump anterior of posterior borders of mesonotal sclerites number 3. (The larva blocks its case opening against predators with its pronotum and anterodorsal and anterolateral mesonotum (= operculum sensu Wiggins 1996; figs. 16.1A, 16.1B) when it withdraws its head.) Mesepisterna (= mesopleurites) each with long and pointed anterior process projecting free from body and fitting against lateral pronotal margin (Fig. 7 m).

Metanotum covered by 4 pairs of coarsely granulated, light-to-medium brown sclerites with sclerite #2 small and relatively weakly sclerotized (Fig. 7).

Legs orange to light brown; coxa of each foreleg wider than those of mid- and hind legs (Figs. 8–10). Coxae of all three legs with ventral groups of dark setae; additional face setae lacking on all femora. Ventral edge of 1 st femur with 2 pale straw-colored spines and 1 dark seta, 2nd femur with 2 dark ventral-edge setae and 3rd femur with 2 dark long and 1 short pale setae. Proximal sections of trochanters without setae. Tarsal claw of each leg curved, with strong basal seta originating from conical base (Figs. 8–10).

Abdomen. Abdominal segment I with 1 dorsal and 2 lateral fleshy protuberances, latter with weak semicircular posterior sclerotization and sclerotized bar extending posterodorsad (Fig. 11). Setal areas sa 1, sa 2, and sa 3 (sensu Wiggins 1996) fused, thereby creating continuous transverse row of setae anterior of dorsal protuberance to dorsal section of each lateral protuberance; small setal group present posterior of dorsal protuberance; setal area sa 3 covering dorsal section of each lateral protuberance (Fig. 11). On abdominal sternum I, setal areas sa 1, sa 2, and sa 3 fused, creating continuous row of setae with basal sclerites minute and inconspicuous; setal number 58–62 (Fig. 12).

Gills consisting of 2–4 filaments and additional single filaments (Fig. 13). Dorsal gills present at most from 3rd segment (postsegmental position) to 7th segment (postsegmental position). Ventral gills ranging from 3rd (presegmental) to 7th segment (postsegmental). Lateral gills lacking. Lateral fringe extending from posterior 1/4 of abdominal segment III to end of abdominal segment VIII.

Posterior margin of abdominal segment IX with 18 setae, 6 of them long and remainder short to medium in length (Figs. 14, 15). Unsclerotized basodorsal section of anal proleg with group of 6–8 short and 3 large, dark setae. Anal proleg lateral sclerite with dark dorsal stripe; anal claw with yellow base and dark brown apical section and with tiny accessory hook (Figs. 14, 15).

Case. Fifth instar larval case flattened, 7.1–9.2 mm long, width at anterior opening 3.9–5.1 mm, at posterior opening 3.0– 3.1 mm, height 2.1–2.4 mm (n = 3), made of mineral particles and consisting of wing-like, large ballast stones up to 5 mm long and 1.7 mm wide along each side, connected by bottom and roof sections made of much smaller sand grains 0.3–1.0 mm in diameter. Compared with other Goeridae, the lateral wing-like extensions (= ballast stones) are small (Fig. 16). Posterior case membrane of prepupae with 5 narrow, oval apertures arranged in a semicircular pattern (Fig. 17).