Mormotomyia hirsuta Austen, 1936

Kirk-Spriggs, Ashley H., Kotrba, Marion & Copeland, Robert S., 2011, Further details of the morphology of the enigmatic African fly Mormotomyia hirsuta Austen (Diptera: Mormotomyiidae), African Invertebrates 52 (1), pp. 145-145 : 149-157

Mormotomyia hirsuta Austen

Figs 1–49, 52

Mormotomyia hirsuta: Austen 1936: 429 .

Redescription of third-instar larva

Measurements: Overall length: 9.5–10.2 mm (mean = 10 mm; SD = 0.21 mm; n = 10); breadth at widest point (abd 3): 1.7–2.6 mm (mean = 1.9 mm; SD = 0.29 mm; n =10).

Colour: Uniformly pure white, except anterior spiracles pale tan-brown and posterior spiracles chestnut-brown around margin of spiracular plate and stigmal openings.

Habitus ( Figs 1 – 3 ): Cylindrical, slightly flattened dorsoventrally, anteriorly and posteriorly narrowed, posteriorly truncate; body segmentation (as labelled on Fig. 3 ) of the usual schizophoran arrangement, divided into pseudocephalon, three thoracic, and seven abdominal segments, plus anal division.

Pseudocephalon ( Figs 5–9 ): Retractile, anteriorly bilobed, slightly longer than wide; each cephalic lobe in area of antenna and maxillary palpus smooth; facial mask ( Fig. 5 , fama) comprising extensive series of oral ridges, those on upper part of fama (immediately posteriad to maxillary palps) formed of fringes of uniform, closely-abutting finger-like digitations ( Fig. 6 ), those on lower fama formed of ratchet-like rows of irregular digitations ( Fig. 7 ), those on lateral sides of cephalic lobes, shorter, rather scallop-like. Labial lobe ( Fig. 5 , llo) in the form of a sub-triangular fleshy, undivided protuberance, posteriad to mouth opening; pseudocephalon separated from pth by distinct fleshy fold, the surface of which is clothed in linear, regular to irregular rows of uniform, often partially overlapping, long pointed spinules. Antenna ( Fig. 5 , ant; 9) apparently one-segmented, relatively large, in terminal position, composed of spherical distal dome ( Fig. 9 , d), inserted into basal ring. Maxillary palpus ( Fig. 8 ) ventrolateral to antenna, with maxillary palpus sensillae and antennal sensillae arranged collectively in a ring and surrounded by three elongated fleshy folds; two a/mp partially separated from three mxps, a/mp slightly larger than mxps. Ventral organ not visible on examined specimens.

Cephaloskeleton ( Figs 28, 29 ): Mouth-hooks drawn-out, with posterior dorsal process truncate, ending in a blunt point; deep black basally, pale yellow-brown centrally and apically, with single well-developed, sharp, posteriorly-directed hooked accessory tooth, campaniform sensilla situated laterally at base of accessory tooth, visible as an elliptical “window”. Intermediate sclerite roughly wedge-shaped (viewed laterally, Fig. 28 ), black, slightly paler on dorsal edge, markedly narrowed basally, acutely pointed at point of connection with basal sclerite, markedly widened in basal third, with small ventral spine, tapering to bluntly pointed apex; H-shaped (viewed dorsally, Fig. 29 ), laterally-expanded and concave at points of connection with mouth-hooks. Basal sclerite ( Fig. 28 , bsc) deep brown-black in area of ventral plate, but becoming markedly paler posteriad to dorsal bridge of dorsal cornu and posterior and lateral regions of the ventral cornu, here weakly sclerotized, in region of cibarium with series of posteriorly-directed lines or ridges. Parastomal bars ( Fig. 28 , pab) attached to basal sclerite, extremely long and narrow for their entire length (needle-like), running above and parallel to dorsal edge of intermediate sclerite. Dorsal bridge ( Fig. 28 , dbr) with cuticular sieve consisting of a network of holes, contiguous with basal sclerite. Dorsal cornu ( Fig. 28 , dcor) broad in region of basal sclerite coming to an acute point, medial margin forming a darker, more heavily sclerotized band or line. Ventral cornu ( Fig. 28 , vcor) broad basally, with dorsally-directed sub-triangular cuticular extension in region of basal plate, more weakly sclerotized centrally, with two acute bars posteriorly, forming dorsal edge of cibarium. Dental sclerite ( Fig. 28 , den) sub-triangular (viewed ventrally), with slight posteroventral indentation, carrying adductor apodemes to mouth-hooks. Epistomal sclerite ( Fig. 29 , epsc) pale black-brown, darker basally and centrally, triangular, with broad, shallow, crescent-shaped excision basally.

Thoracic and abdominal body segmentation ( Figs 1–3, 11–17 ): Three thoracic segments ( Figs 1 – 3 , pth, msth, mtth), each slightly increasing in length posteriad; abd 1–7 of more-or-less equal length, sub-triangular at lateromedial edges; msth, mtth and abd 1–7 each with one dorsolateral and one ventrolateral tubule ( Fig. 11 ), apex furnished with three posteriorly-directed tear-shaped curved processes ( Fig. 12 ); abd 1–7 subdivided into three distinct transverse dorsal and ventral folds ( Figs 1–3 , 13 ), similar, but less pronounced on msth and mtth ( Fig. 1 ); each medial fold with three or four pits (possibly distended in living larvae as the membranous teats described by van Emden) ( Fig. 13 ), dorsomedial pits on msth ( Fig. 13 , dmp) bearing ring of four tear-shaped projections ( Fig. 14 ), dorso-sublateral pits ( Fig. 13 , dslp), with three overlapping leaf-shaped projections arranged in a spiral ( Fig. 15 ); dorsomedial and dorso-sublateral pits on abd 3 similar, but encircled by a “fairy ring” of incurved, sharp spikelets ( Figs 16, 17 ).

Creeping welts ( Figs 1–3 , 18–21 ): Encircling all body compartments on anterior sixth, those on thoracic compartments less pronounced than on abdominal compartments; ventral thoracic welts (e.g., Figs 3 , 18 ) in semi-regular, but widely-spaced crescent-shaped rows, formed of short, blunt, undivided spinules ( Fig. 19 ); ventral abdominal creeping welts (e.g., Figs 3 , 20 ) in similar crescent rows, on broad, raised medial fleshy folds, each comprising closely-packed long-pointed spinules ( Fig. 21 ).

Anterior spiracles ( Figs 26, 27 ): Fan-shaped, located on pth, normally consisting of 18 short, oblong papillae on a broad laterally-expanded lobe-like fleshy projection (retracted into cuticle in Fig. 26 ), each papilla with a slit-like spiracular opening ( Fig. 27 , spiro); ecdysial scar not visible in examined specimens.

Keilin’s organs ( Fig. 10 , ko): On pth closely-separated, consisting of two relatively long, slender, rigid and divergent spike-like sensillae.

Anal division ( Figs 22, 23 ): Large, projecting laterally as three large, cone-shaped projections on either side, surface with multiple and numerous rows of long, pointed spinules, similar to those on ventral creeping welts of abd 1–7 ( Fig. 23 ). Anal pad ( Fig. 22 , ap) transverse, elongate, sub-rectangular, anus surrounded by large, raised, fleshy folds, either side of which has a raised, prominent, medially-directed tubule, encircled with regular, closely-packed rows of brown, long-pointed spinules (these not clearly visible on Fig. 22 ).

Posterior spiracles ( Figs 24, 25 ): On extremely short stigmatophores, each with three radiating, elliptical, long and narrow stigmal openings (stigo) in a shamrock-shaped cuticular depression, surface between them smooth, positioned on a sub-triangular spiracular plate, ecdysial scar large, rounded and conspicuous; with four peristigmal tufts ( Figs 24, 25 , pstgt), inserted between stigmal openings on spiracular plate, broad and blade-like basally with 5–7 long, narrow undivided filaments.

Redescription of puparium ( Fig. 4 )

As described for third-instar larvae, but with following differences.

Overall length (“unhatched” puparia): 6.9–9.5 mm (mean = 7.8 mm; SD = 1.16mm; n =10); width at widest point (abd 2): 1.6–2.6 mm (mean= 2.1 mm; SD= 0.37 mm; n =10).

Male: Overall length (with partially opened puparial caps following eclosion): 8.1–9.7 mm (mean = 8.7 mm; SD= 0.73 mm; n = 10); width at widest point (abd 2): 2.1–2.7 mm (mean= 2.4 mm; SD= 0.17 mm; n =10).

Female: Overall length (with partially opened puparial caps following eclosion): 6.7–6.9 mm (mean= 7 mm; SD= 0.41 mm; n =4); width at widest point (abd 2): 1.7–2.2mm (mean = 1.9 mm; SD= 0.22 mm; n =4).

Shape (n =10), broad, cylindrical, strongly dorsoventrally flattened and markedly wider at anterior end in region of abd 1 and abd 2 (abd 2 normally widest), posteriorly narrowed at abd 7 and andi, posterior end truncate (all puparia examined with a semi-pliable, waxy substance adhering to posterior end, presumably secreted from anus during pupariation), transverse folds, and creeping welts on msth, mtth and abd 1–7 apparent, but less pronounced than larva; dorsal pits, and lateral processes indistinct; deep, lateral, crease-like indentations (allowing articulation) strongly developed between abd 5 & 6 and abd 6 & 7 ( Fig. 4 , indicated with arrows), and two less distinct crease-like clefts on ventral surface of abd 6 & 7. Colour (n =10) pale tan-brown to deep chestnut-brown (pale yellow-brown immediately following pupariation); surface matt, sub-shiny, usually brighter and shinier on thoracic region. Anterior spiracles black basally, with papillae dirty yellow. Posterior spiracles concolourous with rest of puparium. Processes to either side of anal pad, black, strongly developed into hook-like structures, terminal rows of spinules strongly developed.

Description of female reproductive tract

The posterior part of the common oviduct ( Figs 30–32 , co), is lined with membranous cuticle along a considerable portion of its length. This opens anterodorsally into the wide anterior part of the tubular vagina ( Figs 30 , 32 , va). Posterior to this, the paired spermathecae and accessory glands open adjacent to each other into the dorsal vaginal wall.

Each of the two spermathecae ( Figs 30 , 32 , sp1, sp2; 35), consists of a pear-shaped sclerotized chamber, approx. 100 μm in length and 60 μm in width. The surface ( Fig. 35 ) is smooth, with tiny wart-like protrusions, bearing the delicate cuticular end apparatus of epithelial gland cells. The wider apical portion of the spermatheca bears a circular invagination. No introvert is present at the base, but there is a valve-like structure at the insertion of the ducts.

The spermathecal ducts are comparatively short, lined with thick colourless cuticle and are dilated apically, i.e., near the spermathecae and may be slightly sclerotized at their bases.

The accessory glands ( Fig. 32 , ag1, ag2) are almost twice as long as the spermathecae. The large membranous gland lumina receive the delicate end apparatuses of gland cells very similar to those of the spermathecae. The thin-walled ducts are densely pleated, especially towards their bases.

The anteroventral vaginal wall is enlarged to form a deep transversal pouch-like fold ( Figs 30–32 , vf). A small one-chambered, sclerotized ventral receptacle is embedded between this fold and the oviduct ( Figs 30–34 , vr). It arises from the anteroventral portion of the vagina and curves dorsally where it ends in a round chamber. The total length is approx. 70 μm. Only the anterior and dorsal portions of the ventral receptacle are sclerotized. Its shape thus resembles a slipper ( Fig. 34 ) and is reminiscent of a small ephydroid ventral receptacle without operculum.

Where the spermathecal and accessory gland ducts open into the dorsal wall of the vagina, it is drawn out to form a large genital papilla ( Fig. 31 , gp). This papilla protrudes ventrally towards and into the entrance of the ventral receptacle and thus, as long as the vagina is empty, the internal openings of the ducts are in close contact with this organ.

Other than the structures described above, the delicate cuticle of the tubular vagina is devoid of any sclerotized and/or pigmented elements. Posteriorly the vagina opens to the exterior behind sternite 8.

Material examined: Larvae (all labelled “ Mormotomyia / hirsuta Austen, 1936 / det. A.H. Kirk-Spriggs 2011”): 42 “ KENYA: Eastern Prov. / Ukazi [= Ukasi] Hill at: / 00˚49.028’S 38˚32.535’E / 29.xi–1 xii. 2010, 720 m / A.H. Kirk-Spriggs // Extracted from / accumulated bat guano / (1 xii.2010) washed from / rock fissure // Property of the / National Museums / of Kenya, Nairobi [yellow card]” [36 preserved in 96% ethanol; 6 critically-point-dried, mounted on cards; 5 sputter-coated with gold] // BMSA(D) / 26135–26141”; 34 (alcohol-preserved) same except: “Extracted from / accumulated bat guano / (5.xii.2010) washed from / rock fissure // BMSA(D) / 26142” (all BMSA).

Puparia only (all “unhatched” puparia, labelled “ Mormotomyia / hirsuta Austen, 1936 / det. A.H. Kirk-Spriggs 2011”): 16 “ KENYA: Eastern Prov. / Ukazi [= Ukasi] Hill at: / 00˚49.028’S 38˚32.535’E / 29 xi–1. xii. 2010, 720 m / A.H. Kirk-Spriggs // Extracted from / accumulated bat guano / (1 xii.2010) washed from / rock fissure // Property of the / National Museums / of Kenya, Nairobi [yellow card]” [all cardmounted; 1 critically-point-dried, sputter-coated with gold; specimens individually numbered “ BMSA (D) / 26119–26134”] (all BMSA) .

Reared adults (all with associated puparia glued to card pinned beneath; labelled “ Mormotomyia [♂ or ♀] / hirsuta Austen, 1936 / det. A.H. Kirk-Spriggs 2010”): 1♂ “ KENYA: Eastern Prov. / Ukazi [= Ukasi] Hill at: / 00˚49.028’S 38˚32.535’E / 29 xi–1 xii. 2010, 720 m / A.H. Kirk-Spriggs // bat guano washed / from rock fissure // Puparium extracted / from guano: 1 xii.2010 / eclosion: 5 xii.2010 // Property of the / National Museums / of Kenya, Nairobi [yellow card]”; 1♂, 1♀, same, except: extracted: 1 xii.2010 , eclosion: 6 xii.2010; 1♂, 1♀, same, except: extracted: 1 xii.2010, eclosion: 7 xii.2010; 2♂, same, except: extracted: 1 xii.2010, eclosion: 8 xii.2010; 3♂, 1♀, same, except: extracted: 5 xii.2010, eclosion: 5 xii.2010; 3♂, 1♀, same, except: extracted: 5 xii.2010, eclosion: 5 xii.2010; 6♂, same, except: extracted: 5 xii.2010, eclosion: 6 xii.2010; 3♂, same, except: extracted: 5 xii.2010, eclosion: 7.xii.2010; 1♂, 3♀, same, except: extracted: 5 xii.2010, eclosion: 8 xii.2010; 2♂, same, except: extracted: 5.xii.2010, eclosion: 13 xii.2010 [specimens individually numbered “BMSA(D) / 26093–26118”] (all BMSA).

Adult material: 3♀ “ KENYA: Eastern Prov. / Ukazi [= Ukasi] Hill at: / 00˚49.028’S 38˚32.535’E / 29.xi–1. xii. 2010, 720 m / R. S. Copeland ” ( ZSM) .

Figures

Figs 1–11.Scanning electron micrographs of third-instar larva andpuparium of Mormotomyia hirsuta: (1–3) larva habitus, dorsal (1), lateral (2), ventral (3); (4) puparium habitus, lateral (arrows indicate lateral creases allowing articulation);(5–11) larva pseudocephalon,ventral (5), detailof upper oral ridges (6), detail of lower oral ridges (7), maxillary palpus (8), antenna (9); (10) Keilin’s organ on prothorax, ventral; (11) ventrolateral and dorsolateral tubules on first abdominal segment. Scale bars: Figs 1–4 = 1 mm; Fig. 5 = 100 µm; Figs 6–9 = 10 µm; Fig. 10 = 5 µm; Fig. 11 = 50 µm.

Figs 12–21.Scanning electron micrographs of third-instar larva of M.hirsuta: (12) dorsolateral tubule on first abdominal segment,from above; (13) detailof mesothorax indicating positions of dorsal pits; (14) dorsomedial pit on mesothorax; (15) dorso-sublateral pit on mesothorax; (16) dorsomedial pit on third abdominal segment;(17) dorso-sublateral pit on third abdominal segment;(18) creeping welt at junction on mesothorax, ventral; (19) detail of same; (20) creeping welt on second abdominal segment, ventral; (21) detail of same. Scale bars: Figs 12, 14–17, 19, 21 = 10 µm; Fig. 13 = 200 µm; Figs 18, 20 = 50 µm.

Figs 22–29. Scanning electron and light micrographs of third-instar larva of M. hirsuta: (22) anal division, posterior; (23) detail of lateral process on anal division, posterior;(24) posterior spiracular plate, dorsal; (25) detail of peristigmal tuft; (26) anterior spiracle between prothorax and mesothorax laterally; (27) detail of papilla on anterior spiracle; (28) light micrograph of cephaloskeleton, lateral; (29) same, dorsal. Scale bars: Fig. 22 = 200 µm; Figs 23, 28 = 100 µm; Fig. 24 = 20 µm; Fig. 25 = 10 µm; Fig. 26 = 50 µm; Fig. 27 = 5 µm.

Figs 30–31. Light micrographs of internal female reproductive tract of M. hirsuta: (30) cuticular parts, left lateral (one accessory gland lost during dissection); (31) anterior part of vagina with genital papilla, left lateral. Scale bars = 100 μm.

Figs 32–35. Line illustrations of internal female reproductive tract of M. hirsuta: (32) cuticular parts, left lateral (one accessory gland lost during dissection); (33) ventral receptacle, dorsal; (34) same, lateral; (35) spermatheca. Scale bars = 100 μm.

Figs 36–48. (36–42) Scanning electron micrographs of adult male M. hirsuta: (36) tarsomere 1, lateral; (37) same, detail of setation; (38) foretibia, dorsolateral;(39) tarsal claw and pulvillus of foreleg, ventrolateral;(40) same,dorsal;(41) tarsal claw and pulvillus of hindleg, ventral; (42) same, detail of pulvillus, ventrolateral; (43–46) SEMs of Nycteribiidae and Streblidae: (43) Nycteribiidae, tarsal clawand pulvillus of foreleg, ventral; (44) same,detail of pulvillus, ventral; (45) Streblidae (Nycteribosca sp.), tarsal claw and pulvillus of foreleg, ventral; (46) same, detail of pulvillus, ventral; (47, 48) SEMs of female M. hirsuta: (47) wing base, dorsal; (48) halter, dorsal. Scale bars: Fig. 36 = 200 µm; Figs 37, 45, 48 = 20 µm; Fig. 38 = 500 µm; Figs 39, 41, 43 = 100 µm; Figs 40, 47 = 50 µm; Fig. 42 = 10 µm; Fig. 44 = 5 µm; Fig. 46 = 2 µm.

Figs 49–52. (49) Living male of Mormotomyia hirsuta; (50) Ukasi Hill (north face), Kenya, type locality of M. hirsuta, illustrating rock fissure in which flies normally reside; (51) Accumulated deposit of damp bat guano washed from rock fissure on north face of Ukasi Hill, breeding site from which larvae and puparia were extracted;(52)Empty puparium of M. hirsuta (arrowed) attached to fissure wall c. 0.3 metres from substrate. Figs 49, 52 ©R. Copeland, Figs 50, 51 ©A.Kirk-Spriggs.