Ctenophora (Ctenophora) guttata Meigen, 1818

Podeniene, Virginija, Naseviciene, Nijole & Podenas, Sigitas, 2014, Notes on the first instar larvae of Ctenophora and Nephrotoma (Diptera, Tipulidae), Zootaxa 3764 (2), pp. 152-168 : 154-156

Ctenophora (Ctenophora) guttata Meigen, 1818

( Figs. 1–17 )

First instar larvae. Length 2.5–2.6 mm; width– 0.44–0.45 mm. Body covered with pale pubescence. Cuticle is transparent.

Head capsule. Length 0.41–0.43 mm; width 0.24–0.25 mm. Head capsule is prognatous and hemicephalic, oval in shape, slightly depressed dorsoventrally and differently from the head capsule of the last instar larvae, just slightly sclerotised ( Figs. 1, 2 ). Internolateralia and externolateralia are separated by incisions, which reaches almost half-length of head capsule. Each incision is continuous with deep groove (the most sclerotised part of head capsule) that extends almost to the base of antenna. Externolateralia are widely separated on the ventral side of capsule ( Fig. 2 ). Premaxillary suture separates side plates from the rest of head capsule. Side plate is wedge shaped with anteromedially situated long seta. Hypostomium bears six large sharp teeth ( Fig. 3 ). Basally it is fused with ventral margins of genae and with side plates. Prementum is visible from below. It has three large sharp teeth on anterior margin. A pair of labial palps is present in the middle part of prementum, each consisting of five peg-like sensillae. Labial palps are separated by cushion of short bristles ( Fig. 4 ). Frontoclypeus is fused with internolateralia. Clypeal part of frontoclypeus is membranous and separated from labrum by deep fold. One long seta and three sensory pits present on the anterior part of clypeus, one long and one short seta present near the base of antenna. Three very short bristles are located near the grove on both sides of clypeus ( Fig. 1 ). Ecdysial and coronal sutures are not visible. Labrum is trapezoidal in shape and dorsally is composed of two wedge-shaped sclerotised plates separated by membranous area ( Fig. 5 ). Apical part of labrum and ephipharynx are covered with numerous short hairs. One long seta and one short sensory peg present on membranous part on both sides of labrum. One long, one of medium length, two short setae and three sensory pits present on anteriolateral part of labral lobe. One long and one short seta are located on posterior part of labral lobe. Antenna is short, slightly tapering apically. It has just one cylindrical segment, which length is almost two-thirds the width ( Fig. 6 ). Apically it has one large cone-shaped and six small peg-like sensillae, dorsally it has a sensory pit near the base. Mandible is one segmented and more sclerotised than the rest of head capsule. Five sharp teeth are present on each mandible ( Fig. 7 ). Second dorsal and second ventral teeth are much smaller than apical, first ventral and dorsal teeth. Prostheca or lacinia mobilis present on the dorsal side of mesal mandibular base ( Fig. 7 ). Lacinia mobilis is archshaped, with 11–12 sharp small teeth on apical part and with cushion of short hairs in the middle. Lateral margin of mandible has two long setae near the base. A sensory pit is present at the base of dorsal side of mandible. Mandibles operate in horizontal plane. Inconspicuous larval eye spots present below the base of mandible. Maxilla has wedge-shaped cardo, bearing two almost equal setae near the distal end ( Fig. 8 ). There are two sclerites on stipes. The inner sclerite extends around inner margin of maxilla onto its dorsal surface. The outer sclerite extends around outer margin of maxilla to its dorsal surface. There is a diamond-shaped sclerite near the base of galea ( Fig. 8 ). Galea and lacinia are fused. Galea is covered with numerous short hairs. There are three long sensory structures on the ventral side of galea. Lacinia bears five sharp pointed outgrooves on the outer margin.

Thorax. All thoracic segments are short and wide, covered with microscopic hairs. The first thoracical segment has no welts ( Figs. 9, 10 ).

Abdomen. Abdominal segments are longer than wide. They are covered with two types of hairs. Short hairs cover lateral parts of segments and large partions of tergal and sternal parts ( Figs. 11, 12, 13 ). Long hairs form transversal lines on tergal and sternal parts ( Figs. 11, 12 ). Setae are light brown. Setae D1–D4 and D6 are long, more than five times as long as D5. Setae D2, D3 and D5, D6 are very close to each other ( Fig. 14 ). Setae V1 and V3 are very long. They are twice as long as V4 and almost five times as long as V5. Setae V1, V2 and V4, V5 are very close to each other ( Fig.15 ). Seta L3 is very long. It is slightly longer than L2, twice as long as L1 and more than six times as long as L4. Setae L1, L2 and L3 are very close to each other ( Fig. 16 ).

Hairs on sixth and seventh abdominal segments are longer than those on other segments. Third thoracic and first abdominal segments are wider than longer. First, second thoracic and second–eighth abdominal segments are longer than wide. Last or anal abdominal segment is constricted.

Spiracular disc. Spiracular field is surrounded by four flat and elongate round-tipped lobes ( Fig. 17 ), which are almost completely covered with large, wedge-shaped sclerites. Lateral pair is more prominent. Lateral lobe is almost as long as its width at the base. It has four long stout apical bristles. Each bristle is almost five times as long as the lobe. Length of ventral lobe is almost 1.5x its width at the base. The lobe has one long and one mediumlength apical bristles and single long bristle on inner and on outer margins. They are as long as the lobe. It also has one of medium-long setae and a short bristle on outer margin. There are four tufts of longer and shorter bristles above the each spiracle. The innermost tuft consists of three short bristles. Laterally from it, is tuft of four very long bristles (they are almost three times as long as bristles of the innermost tuft). Further laterally, is tuft of three long bristles and outermost is one long bristle. Spiracles are large, circular and close to each other. Distance between them is smaller than diameter of a spiracle.

Anal field. Anus is surrounded by four short, white and fleshy anal papillae. A few long setae present on anal segment.

Specimens examined. 93 egg-larvae from 1 female, which was captured in Vilnius, N54.68194, E25.27087, 12 VI 2011, eggs were laid on 13 VI 2011, egg-larvae hatched on 19 VI 2011.

Figures

FIGURES 1 – 10. Ctenophora (Ctenophora) guttata, first instar larva: 1. General view head capsule, dorsal aspect. 2. General view head capsule, ventral aspect. 3. Hypostomium. 4. Prementum. 5. General view of labrum. 6. Right antenna. 7. Mandible. 8. Right maxilla, ventral view. 9. The first thoracical segment, dorsal view. 10. The first thoracical segment, lateral view.

FIGURES 11 – 17. Ctenophora (Ctenophora) guttata, first instar larva: 11. Abdominal segment, lateral view. 12. Abdominal segment, dorsal view. 13. Abdominal segment, ventral view. 14. Dorsal abdominal setae (segments II – VII). 15. Ventral abdominal setae (segments II – VII). 16. Lateral abdominal setae (segments II – VII). 17. Spiracular field.