Palaeosynthemis cyrene (Lieftinck, 1953)

Fleck, Günther & Adouzi, Marine El, 2013, The larva of the genus Palaeosynthemis Förster, 1903 (Odonata: Anisoptera: Synthemistidae) and a generic key to the larvae of non-New Caledonian Synthemistidae, Zootaxa 3619 (5), pp. 589-594 : 589-593

Palaeosynthemis cyrene (Lieftinck, 1953)

Description (F-0). Larva of typical synthemistid type, elongated and rather robustly built, with general color of the body brownish and abdomen remarkably patterned with green, yellow and orange with white spots ( Figs. 1, 2 ); larva covered by small scale-like setae and distinctly pilose, with long and strong pale setae predominantly distributed on frontal margin, on lateral parts of the body, and on trochanters, femora and tibiae.

Head appearing rectangular in dorsal view, as broad as thorax ( Figs. 1–3 ); antennae thick and rather short, little shorter than length of head, 7-segmented with following anterodistal relative length of antennomeres: 0.5, 0.5, 0.8, 0.6, 0.7, 1.0, 0.8, and with long setae essentially located along lateral margins ( Fig. 4 ); frontal plate wide, almost semicircular with apex slightly flattened, and with rather long, robust and curved setae on distal margin, and scalelike setae on dorsal surface ( Fig. 4 ); functional part of eyes small, located antero-laterally, slightly projected above the epicranium; occiput well developed, with subparallel lateral margins, and with posterior margin slightly concave; occipital postocular lobe with dense fringe of long setae made by numerous soft hair-like setae and several well-aligned stronger and rigid setae; mask rather short and broad, submentum-mentum articulation just reaching level of mesothorax ( Fig. 2 ); submentum very large and with posterior margin distinctly bilobed ( Figs. 2 , 5); prementum very abruptly widened at level where submentum disappears beneath prementum (ventral view, Figs. 2 , 5); ventral side of mask with premental groove short but very distinct (see Theischinger & Fleck 2003); prementum with laterodorsal parts furnished with field of small strong spine-like setae, with two series of 11–12 premental setae (one specimen with 10 setae on right side), 4–5 most lateral ones longest (Fig. 5); between mental setae and distal margin of prementum presence of field of fine spine-like setae; distal margin of prementum of libelluline type, finely undulated laterally with apical large tonguelet, between two lateral undulations presence of a minute seta (Fig. 5); palpal articulation surmounted by small spine-like setae (Fig. 5); labial palps with field of about 11–16 minute setae close to articulation, and with 4 palpal setae each, dorsal margin of labial palps with row of numerous long and soft setae (Fig. 5); dentations of labial distal margin deprived of raptorial setae, each of these dentations with ventro-apical hooklet and row of ventral minute serrations (Fig. 6); concave part between two palpal dentations large and rounded; moveable hooks strong and rather long, longer than half length of palpal distal margin (Fig. 6).

Prothorax less wide than head, with distinct and grossly rounded epaulets ( Figs. 3 , 7); synthorax robust, with wing sheaths strongly divergent, reaching or overlapping posterior margin of S4 tergite ( Figs. 1–3 ), and with ventral posterior oblique sulci meeting transverse one nearly in one median point ( Fig. 2 ); legs long and strong, with tibiae bearing some long spine-like setae near apex of flexor part, and with rather short claws about same length as that of first tarsomere (ventral view).

Abdomen elongated and tapered, approximately twice as long as head and thorax taken together (on exuviae); pleurite entire, not divided into prepleurite and postpleurite; female rudiments of ovipositor visible at base of S9 as two small blunt triangular buds (Fig. 8); anal pyramid well developed, about 1.5 (larvae) to 1.2 (exuviae) times longer than dorsal length of S9+S10 taken together ( Fig. 3 ); epiproct and paraprocts of about equal length (Figs. 9, 10) and curved down with curvature of epiproct more pronounced than that of paraprocts (Figs. 9b, 10b); epiproctal rudiment of male inferior appendage well marked and with distal margin truncated (Fig. 9a); male cerci with apices slightly divergent (dorsal view) and distinctly broader than female cerci which are triangular-shaped in lateral view and with apices slightly convergent (dorsal view) (Figs 9, 10).

Measurements (mm). Total length, male exuviae 24.0–25.0, female exuvia 26.0, male larva 23.0, female larva 25.0; width of head, male exuviae 5.5–5.6, female exuvia 5.9, male larva 5.5, female larva 5.9; greatest width of abdomen (S5), male exuviae 5.8–6.3, female exuvia 6.1, male larva 6.0, female larva 6.3.

Note on biology. A rather mature F- 1 P. cyrene male larva, collected 8.XII.2004, moulted to F-0 on 5.IV.2005, and to adult the 27.IX.2005, nearly one year after its collecting. A second F- 1 P. cyrene male larva, collected 9.XII. 2004 in a similar stream distant a few hundreds of meters from that of the first male F-1, and distinctly less voracious, moulted to F-0 on 20.IV.2005 and was put in ethanol as mature larva (pterotheca slightly inflated, and adult eyes already visible beneath larval cuticle) on 5.II.2006. Thus the larval stage should extend over at least two years, more probably three. The great disparity observed in the length of the last instar could correspond to two adaptive strategies within the species. Nevertheless, rearing in the laboratory could introduce a great bias.

Genus Palaeosynthemis Förster, 1903 . The proposed generic diagnosis follows the model of diagnoses established by Theischinger (2001) for Australian synthemistids and gomphomacromiids.

Diagnosis (F-0). (1) Frontal plate well-developed, reaching to end of pedicels, or slightly passing them, and with numerous strong curved setae along distal margin; (2) prementum as broad as long, with generally 4–5 pairs of primary and 6–7 secondary premental setae, and with distal lobe of prementum distinct and rather large; (3) labial palps with 4–5 dentations, shark’s fin-shaped with ventro-apical small indentation; (4) generally 4 palpal setae; (5) postocular lobe with dense fringe of very long setae, any of them rigid; (6) lateral margin of pronotal lobes with fringe of very long and robust setae; (7) abdominal terga without any processes, hairy; (8) cerci approximately half length of paraprocts.

Note. This diagnosis is based on a single species unambiguously determined and is therefore susceptible to change with the discovery of new larvae. For example, some synthemistid larvae collected at Varirata plateau (26–27.XI.2004, about 800 m asl), near Port Moresby, for which rearing failed, and then not attributed to any species, present a distal margin of the frontal plate with curved and rather short scale-like setae and an anal pyramid slightly shorter than that of P. c y re n e.

Affinities. Similar to Archaeosynthemis and Synthemis , and probably related to these genera; distinguished by the shape of palpal dentition, the shape of frontal plate and the abruptly expanded prementum.

Figures

FIGURE 3. Drawing of the general habitus of the last instar (exuvia). Setae omitted.

FIGURE 4. Frontal plate and right antenna, dorsal view. FIGURE 5. Mask, dorsal view. FIGURE 6. labial palps, frontal view. FIGURE 7. left pronotal epaulet. FIGURE 8. Female S 9 showing the rudiments of ovipositor (exuvia), ventral view, setae figured only on left side. FIGURE 9. Male anal pyramid, a) dorsal view, b) lateral view. FIGURE 10. Female anal pyramid, a)

FIGURES 1 – 2. photographs of last-instar larva showing the peculiar color pattern: 1) dorsal view; 2) ventral view.