Colobaea, Zetterstedt, 1837

Bratt, Albertus D., Knutson, Lloyd V., Murphy, William L. & Daniels, Anthony A., 2020, Biology, immature stages, and systematics of snail-killing flies of the genus Colobaea (Diptera: Sciomyzidae), with overviews of aspects of the tribe Sciomyzini, Zootaxa 4840 (1), pp. 1-64 : 55

Keys to third-instar larvae and puparia of Palearctic species of Colobaea

The only keys to genera of larvae and puparia of Palearctic Sciomyzidae are those of Rozkošný (2002) and Knutson & Vala (2011). Rozkošný (2002) provided a key to the puparia of two species of Colobaea ( C. distincta and C. pectoralis ).

Key to larvae

1 Posterior end with two pairs of reduced, welt-like lobes ( Fig. 16 ); dorsal surface of segments XI–XII tanned, with many fine scales ( Fig. 22 ); anterior spiracles with 14–20 large, fingerlike papillae ( Fig. 35 ). In species of Lymnaeidae . Ireland to Kazakhstan, northeastern Siberia, Russian South Maritime Territory......................................... C. bifasciella

– Posterior end with four pairs of conical lobes ( Figs 15, 17–19 ); dorsal surface of segments XI–XII smooth, white; anterior spiracles with 12–16 small papillae. Various snail prey........................................................ 2

2 Anterior spiracles with 12–14 marginal papillae ( Fig. 33 ); posterior spiracular plates with margins projecting at ends of slits ( Fig. 30 ). In Gyraulus intermixtus . Iran, Pakistan................................................... C. deemingi

– Anterior spiracles with 14–16 marginal papillae ( Fig. 34 ); posterior spiracular plates subcircular. In species of Anisus , Bathyomphalus , Planorbis , and Lymnaeidae . Widespread in Europe and Middle East....................................... 3

3 Dorsal cornu of pharyngeal sclerite longer than ventral cornu, posterior margin of dorsal cornu irregular, slender; dorsal and ventral cornua converging posteriorly ( Fig. 40 ). In Radix peregra and species of Planorbis . Trans-Palearctic east to eastern Siberia, south to Egypt, Israel.................................................................... C. punctata

– Dorsal and ventral cornua subequal in length, posterior margins less irregular, dorsal and ventral cornua not converging posteriorly ( Fig. 41 ). In Anisus vortex and Bathyomphalus contortus . Trans-Palearctic east to Moscow and northern Kazakhstan; absent from southeastern Europe................................................................ C. pectoralis

Key to puparia

1 Robust form; anterior half expanded to close opening of snail shell whorl, posterior half smaller, twisted; anterior spiracles large, protrudent, with 14–20 large papillae ( Figs 24, 27 ). In species of Lymnaeidae . Ireland to Kazakhstan, northeastern Siberia, Russian South Maritime Territory........................................................... C. bifasciella

– More slender; anterior end expanded to fit tightly within snail shell whorl, body form crescent shaped or subcylindrical in lateral aspect, not twisted; anterior spiracles protrudent or sessile, with 12–16 small papillae. In various species of snails..... 2

2 Anterior spiracles small, sessile; posterior spiracles large, protrudent; dorsal cephalic cap widened to close shell whorl, then narrowed abruptly ( Figs 45–46 ). In Gyraulus intermixtus ; septum material may be present. Southwestern Iran, Pakistan............................................................................................... C. deemingi

– Anterior spiracles large, protrudent; posterior spiracles small, not protrudent; anterior end widened to close shell whorl but not abruptly narrowed ( Figs 23, 26 , 47–48 ). In species of Anisus , Bathyomphalus , Planorbis , and Lymnaeidae . No septum material present.............................................................................................. 3

3 Form slender, dorsoventrally compressed, crescent shaped in lateral aspect; anterior spiracles slender, strongly projecting anteriorly ( Figs 23, 26 ). In Anisus vortex and Bathyomphalus contortus . Ireland east to Moscow and northern Kazakhstan..... ............................................................................................ C. pectoralis

– Form robust, subcylindrical, not dorsoventrally compressed; anterior spiracles subcircular, projecting dorsally ( Figs 47–48 ). In Radix peregra and species of Planorbis . Trans-Palearctic to eastern Siberia, south to Egypt, Israel............. C. punctata

Figures

FIGURES 15–20. Posterior ends of third-instar larvae: 15, Colobaea americana Steyskal, caudal view; 16, C. bifasciella (Fallén), caudal view; 17, C. pectoralis (Zetterstedt), caudal view; 18, C. punctata (Lundbeck), caudal view; 19, C. deemingi Knutson & Bratt, caudal view; 20, C. punctata, lateral view.Abbreviations: DL, dorsal lobe, LP, lateral pad, M, mammillae, PaP, peri-anal pad, SpP, spiracular plate, SpT, spiracular tube, VL, ventral lobe, VlL, ventrolateral lobe. Measurement in mm.

FIGURES 21–22. Colobaea bifasciella (Fallén), third-instar larvae: 21, lateral view; 22, dorsal view. Abbreviations: ASp, anterior spiracle; CpS, cephalopharyngeal sclerite; LP, lateral pad; IDSP, intrasegmental dorsal spinule patch; PaP, peri-anal pad; PIF, primary integumentary fold; PSp, posterior spiracle; SIF, secondary integumentary fold; VL, ventral lobe; VIL, ventrolateral lobe. Measurement in mm.

FIGURES 32–35. Anterior spiracles, third-instar larvae: 32, Colobaea pectoralis (Zetterstedt); 33, C. deemingi Knutson & Bratt; 34, C. punctata (Lundbeck); 35, C. bifasciella (Fallén). Abbreviations: PrS, prismatic spot; StS, stigmatic scar. Measurement in mm.

FIGURES 28–30. Posterior spiracular plates: 28, Colobaea americana Steyskal, first-instar larva; 29, C. deemingi Knutson & Bratt, first-instar larva; 30, C. deemingi, third-instar larva. Abbreviations: FH, float hair; PGO, perispiracular gland opening. Measurement in mm.

FIGURES 40–43. Cephalopharyngeal skeletons of third-instar larvae: 40, C. punctata, lateral view; 41, C. pectoralis, lateral view; 42, C. bifasciella (Fallén), lateral view; 43. C. deemingi Knutson & Bratt, lateral view. Abbreviations: AvP, anteroventral process of pharyngeal sclerite, DB, dorsal bridge, DC, dorsal cornu, DW, dorsal window, ES, epistomal sclerite, HS, hypostomal sclerite, LS, ligulate sclerite, MH, mouthhook, PB, parastomal bars, PS, pharyngeal sclerite, VA, ventral arch, VC, ventral cornu, VW, ventral window. Measurement in mm.

FIGURES 23–27. Puparia: 23, Colobaea pectoralis (Zetterstedt), lateral view; 24, C. bifasciella (Fallén), lateral view; 25, C. americana Steyskal, dorsal view; 26, C. pectoralis, dorsal view; 27, C. bifasciella, dorsal view. Measurement in mm.

FIGURES 44–48. Puparia, lateral and dorsal views: 44, Colobaea americana Steyskal, lateral view; 45, C. deemingi Knutson & Bratt, lateral view; 46, C. deemingi, dorsal view; 47, C. punctata (Lundbeck), lateral view; 48, C. punctata, dorsal view. Measurement in mm.