Terellia (Cerajocera) tussilaginis (Fabricius, 1775)

Troshyn, A. M., 2024, Description Of The Third Instar Larvae Of Terellia Tussilaginis And T. Gynaecochroma (Diptera, Tephritidae), Zoodiversity 58 (2), pp. 167-174 : 168-170

Terellia (Cerajocera) tussilaginis (Fabricius, 1775) ( figs 1 –2)

M a t e r i a l e x a m i n e d. Ukraine, Kryviy Rih District, Gleyuvatka, in flower heads of Arctium lappa L.

25.10.2023, 3 third instar larvae (A. Troshyn leg.).

D e s c r i p t i o n. Third instar larva. Body short oval; 2.54–3.1 mm long (mean 2.78 mm); 1.74–2.0 mm wide (mean 1.84 mm); 1.45–1.55 times as long as wide (mean 1.51 mm). Coloration. Uniform, pale yellow to pale orange. Posterior surface of segment 8 yellow light.

Gnathocephalon ( fig. 1 , 5) mostly smooth, inverted into thoracic segment 1 at rest. Anterior sensory lobes short, partly separated at anterior margin. Antenna (dorsal sensory organ) ( fig. 1 , 5: ant) with short, rounded terminal segment. Maxillary sense organ ( fig. 1 , 5: max. org) with sensilla. Medial sensory organ indistinct or absent. Anterior portion of sensory lobe with network of grooves. Antero-lateral portion of gnathocephalon with 10–12 oral ridges ( fig. 1 , 5: or rdg). Lateral sensory organ ( fig. 1 , 5: lso) distinct. Stomal sensory organ and labial lobe not examined. Dorsal surface of gnathocephalon with additional sensilla ( fig. 1 , 5: s) posterior of oral ridges. Postero-lateral portion of gnathocephalon with rather numerous small and acute denticles.

2 3

Fig. 2. Terellia tussilaginis , larva. 1 — cephalopharyngeal skeleton; left; 2 — segment 8, posterior view; 3 — posterior spiracle: arr — arcuate row of plaques; D1, D2 — dorsal sensilla 1 and 2; da — dorsal apodeme; dc — dorsal cornu; es — ecdysial scar; hs — hypopharyngeal sclerite; I1/2 — intermediate sensilla 1 and 2; L — lateral sensillum; mh — mouthhook; msc — mandibular sclerite; ps — posterior spiracle; psma — plaques of submedial area; pt — praeapical tooth; s — sensillum; ss — spiracular slits; sh — spiracular hair; sta — stigmatal area; stp — stigmatal plate; trr — transverse ridge of plaques; V — ventral sensilla; va — ventral apodeme; vc — ventral cornu.

Cephalopharyngeal skeleton (fig. 2, 1). Mandibular sclerite (fig. 2, 1: msc) almost as long as high, with single blunt mouthhook (fig. 2, 1: mh) and without additional lobes or teeth. Preapical tooth (fig. 2, 1: pt) at most vestigial, barely visible; dorsal and ventral apodemes (fig. 2, 1: da, va) about as high as long. Hypopharyngeal (= hypostomal) sclerite (fig. 2, 1: hs) moderately long, ca. two times as long as high, parastomal sclerite fused to it, indistinct. Dental sclerite not expressed. Pharyngeal sclerite and dorsal and ventral cornu (fig. 2, 1: dc, vc) visible, but details not clear.

Thoracic segments 1–3 moderately sclerotised. Segment 1 short, forming a shield-like “mask” ( fig. 1 , 5) with T-shaped aperture when gnathocephalon retracted; antero-dorsal surface with denticles. Anterior spiracle ( fig. 1 , 4 ) with 7 lobes. Segments 2–3 almost smooth.

Segment 8 (fig. 2, 2) with rows of denticles at anterodorsal margin and with 10– 11 elongate-oval or subrectangular plaques forming arcuate ridge (fig. 2, 2: arr) between stigmatal and dorsal areas. Stigmatal area with slightly sunken spiracular plates (fig. 2, 2: stp) separated by a rather wide area 1.2 times as wide as spiracular plate and bearing 6– 7 subrectangular plaques (fig. 2, 2). Medial area separated from stigmatal area by transverse arched ridge (fig. 2, 2: trr) formed by plaques. Submedial area with 5 oval plaques (fig. 2, 2: psma) forming two irregular rows. Intermediate sensilla ( fig. 4 , 2: I1 and I2) present, close to each other. Dorsal sensillum (fig. 2, 2: D1 and D2), lateral sensillum (fig. 2, 2: L) and ventral sensillum (fig. 2, 2: V) seem to be present, but not depicted in fig. 2, 2). Other sensilla to be expected (see White et al., 1999, Fig. 33.7) not visible.

Posterior spiracle (fig. 2, 3) with three spiracular slits (fig. 2, 3: ss). Dorsal slit almost vertical, two times as long as wide. Medial and ventral slits 2.4–2.7 as long as wide; ventral slit almost horizontal, forming angle about 120° to dorsal slit. Bundles (from dorsal to medioventral) with 3–4 — 2–3 — 3 — 2–3 spiracular hairs (fig. 2, 3: sh).

Diagnosis. Third instar larva of T. tussilaginis differs from all known larvae of Terellia subgenus Cerajocera by the absence of a sclerotized prominence on abdominal segment 8. From other known larvae in species of the genus Terellia , it differs by the less sclerotized last abdominal segment and the number of plaques on it.

Notes. This species is widespread in Europe and in some regions of the Far East, in particular, on Sakhalin Island. First instar larvae develop in flower heads of Arctium lappa L. and the 2–3rd instar larvae develop in the burdock seeds ( Korneyev, 1987). Superficially similar T. (C.) nigronota ( Korneyev, 1985) occurs in Eastern Europe, and the Caucasus ( Korneyev, 1985), also in association with burdocks, but larvae have not been collected or described yet.

Figures

Fig. 1 4. Terellia tussilaginis, larva. 1 — habitus, left; 2 — habitus5, ventral; 3 — larvae in seed; 4 — anterior spiracle; 5 — gnathocephalon, anterior view: ant — antenna; lso — lateral sensory organ; mh — mouthhook; max org — maxillary sensory organ; or rdg — oral ridges; s — sensillum.

Fig. 4. Terellia gynaecochroma, larva. 1 — anterior spiracle; 2 — segment 8, posterior view; 3 — stigmatal area, enlarged; 4 — posterior spiracle: es — ecdysial scar; I1/2, I3 — intermediate sensilla 1, 2 and 3; ss — spiracular slits; sh — spiracular hair; sp — sclerotized prominence; V — ventral sensilla.