Diaphorocera chrysoprasis

Turco, Federica, Giulio, Andrea Di & Bologna, Marco A., 2006, The first larval description in the genus Diaphorocera Heyden (Coleoptera: Meloidae: Cerocomini): D. chrysoprasis Fairmaire, Zootaxa 1295 (1), pp. 29-39 : 31-37

Diaphorocera chrysoprasis ,

vial 518 (about 50 triungulins); slide M403 (2 triungulins); stub 104 (2 triungulins): Tunisia, Gouvernatorat de Tozeur, 10 Km SW Tozeur on road P3, 33,90188° N 8,02700° E, 27.IV.2004, F. Turco, S. Carloni and C. Settanni leg., on Chrysanthemun coronarium ( Asteraceae ), one deposition 3.V.2004, hatch 26.V.2004 .

Morphological analyses were performed by a Leitz Laborlux S light microscope for material cleared and mounted on slides in Canada balsam, and a Philips XL30 scanning electron microscope for material mounted on stubs, after critical point dehydration and gold sputtering. Measures reported in the description are the mean of those of slidemounted larvae. For nomenclature of larval morphological features we refer to MacSwain (1956) and Bologna and Pinto (2001). For some characters of larval chaetotaxy we adopted notational conventions suggested by Selander (1990).

Results

Egg morphology

Eggs are whitish, elongate, rounded at both ends and distinctly wider at one apex. Egg length: 1 mm; maximum diameter: 0.3 mm.

Description of first instar larva

Habitus ( Figs. 9–10 ). Triungulin campodeiform; body elongate, subcylindrical, subparallel­sided.

Measurements. Body length 1.630 mm (from pygidium to labrum); head length 0.212 mm (from occipital foramen to clypeolabral suture), maximum width 0.316 mm, width at base (occipital foramen) 0.256 mm; basal stem of epicranial suture 0.063 mm; antennal length 0.063 mm, antennal terminal seta length 0.067 mm; prothorax length 0.200 mm, maximum width 0.368 mm; abdominal length 0.900 mm, abdominal terminal setae length 0.588 mm; diameter of spiracles: mesothoracic about 21 m, abdominal I about 15 m, abdominal II–VIII respectively from 11 to 9 m.

Colour. Whitish with head, tergites, legs and laterotergites light brown; thoracic sternites not evidently sclerotised.

Microsculpture. Cuticle reticulate with transverse polygonal meshes.

Head ( Figs. 1 , 11–12 ). Very transverse with subparallel sides greatly rounded posteriad; basal elevation absent; anterior margin of head slightly convex. Epicranial suture Y­shaped; frontal sutures complete to antennal fossae, widely diverging at base, then parallel and markedly curved laterally at distal third. One stemma present on each side of head capsule, dorsally placed; stemmata convex, round, subequal in diameter to mesothoracic spiracle. Frontoclypeal region with a total of 14 setae subequal in length; boundary between clypeus and frons with a transverse row (frontoclypeal row, FCR) of 3 pairs of setae; sensory pit between FCR 2 and FCR 3; 4 pairs of setae posterior to FCR, following a curved line paralleling the arms of the epicranial suture (from posterior to anterior setae 1–4); sensory pits present between setae 1 and 2; each epicranial plate, dorsally on posterior half, with 4 very small setae longitudinally arranged in the middle of the plate and with 2 pits at both sides; 4 pairs of setae transversally lined at the level of the base of frontal arms of epicranial suture; 1 sensory pit and 2 small setae just anterior to the previous line; 3 setae around the stemma: the first anterior, just behind antennal fossa; the second external and at the same level of stemma; the third medial (ocular seta), at the same level of stemma; ocular seta slightly longer than the adjacent, posterior to ocular sensory pit. Epicranial plate ventrally with 3 setae: 2 lateral and 1 near the base of mandible. Gulamentum weakly sclerotised with 2 anterior setae. Antennae short, forwardly directed ( Figs. 2 , 13 ); antennomere I short, ring­like with 1 dorsal and 1 dorsolateral sensory pit; antennomere II about 1.5 times longer than I, with 4 setae (1 dorsal, 1 lateral on outer side, 1 short ventro­lateral on inner side, 1 small ventro­lateral seta on the outer side) near sensory appendix and 1 dorsolateral pit; sensory appendix on segment II ventral, conical, acute at apex, nearly as long as antennomere I; antennomere III cylindrical, stout, about as long as antennomere II, with a long apical seta, as long as the antennomeres II and III together (ratio apical seta/head length: 0.3, see Table 1 ); 3 subapical setae, 2 dorsolateral and 1 medioventral; one small seta near the base of apical seta, and 1 lateral pit on outer side of the segment. Labrum transverse, with straight anterior margin and rounded sides, with 8 dorsal setae of different sizes approximately distributed along the margin; 8 very small setae and 2 pits anteroventrally. Epipharynx with the aspect of a coarsely granular plate. Mandibles dorsoventrally flattened, with a troncoconical base and apical half narrowing and bending inward, without mola ( Fig. 4 ); cutting edge with 6 little distinct teeth; outer margin of mandible with 2 setae and 1 sensory pit between them; 1 pit mesodorsally. Maxillae with broad stipes with 1 extremely long seta (as long as the maxillary palpus), 1 long seta laterally and 2 short setae and 2 pits basally ( Figs. 3 , 14 ); mala simple, lobiform, protruding, with 8–10 thick setae; maxillary palpomere I short, ring­like, with 1 pit ventrally; segment II asymmetric, short and straight at inner side, longer and curved at outer side; palpomere II with 2 lateral setae, 1 longer (outer side) and 1 small (inner side); palpomere III subcylindrical, more than 2 times longer than I, with swollen apex; palpomere III with 1 small dorsolateral seta (inner side) and 1 apical, stout, subconical sensory appendix, inserted in a prominent base and surrounded by a crown of 11 shorter subconical papillae; outer side of palpomere III furrowed by 1 slender digitiform and 1 pit sensillum; cardo transverse, subrectangular, with 1 very small lateral seta. Labium with mentum bearing 1 pair of small setae and 1 pair of sensory pit basally; prementum with 1 pair of medial setae and 1 pair of basal sensory pits; 2 small ligular setae near the insertions of palpi on prementum; labial palpomere I short and broad, II cylindrical, twice longer than I, with an apical sensory complex similar to that of maxillary palpomere III; 1 sensory pit lateroventrally (outer side).

Thorax. Segments transverse, subrectangular, decreasing in width from prothorax to metathorax, with anterior and posterior margins only slightly curved; meso­ and metanotum more rounded than pronotum laterally. Ecdysial line well marked and complete on pro­ and mesonotum and absent on metanotum. Pronotum subrectangular, broader than head, about 1.8 times wider than long ( Fig. 5 ); 13 setae (12 long and 1 short) and 3 pits present symmetrically at each side of the ecdysial line, approximately disposed in 3 transverse, subparallel rows; anterior row (AR) with 5 long setae and 2 pits (1 small and short anterolateral seta on membrane); medial row (MR) with 3 setae and posterior row (PR) with 5 setae (4 long and 1 short) and 1 pit; prosternum with 3 pairs of medial setae of different length, medial pair shorter and posterior pair longer than anterior pair and 2 pairs of small anterior setae more lateral. Mesonotum distinctly narrower than pronotum and slightly broader than metanotum; AR composed of 4 setae and 1 pit extremely small and short compared to those of pronotum. MR with 3 long setae and 2 shorter near the stigma; PR with 4 long setae and 2 pits; 3 pairs of medial setae on mesosternum slightly increasing in length from anterior to posterior and 1 pair of small anterior setae more lateral. Setae of metathorax similar in number, position and relative dimensions to those of mesothorax.

Legs. Slender; coxa short and broad, with 3 long setae, transversally lined (gradually decreasing in size from the external to the internal), 2 setae and 1 pit lateral (inner side), 2 small and short setae and 1 pit basally; trochanter with 5 setae and 6 pits (1 subapical and 5 transversally disposed); 8 setae and 1 pit on femur, the major ventral femoral seta, much shorter than femur; tibiotarsi and claws increasing in length from fore to hind leg; tibiae with 5 longitudinal rows of 5–7 robust setae; claw thin, acute and slightly curved at apex, with 2 sub­basal setae of different length, slightly displaced at base, the distal longer than the proximal seta and approaching apex ( Fig. 15 ); surface of claws longitudinally ridged.

Spiracles ( Fig. 16 ). Rounded, internally papillate; marginal ring slightly protruding (as in Fig. 6 ); mesothoracic spiracle anterolateral, about as large as the stemma; abdominal spiracle I dorsolateral ( Fig. 6 ); abdominal spiracles II–VIII on laterotergites, smaller than I and all about equal in size.

Abdomen ( Figs. 9–10 ). Subparallel sided with transverse, rectangular terga, well sclerotised; abdominal segments IV–IX gradually decreasing in size; tergum completely fused with laterotergites on segments I and IX, only partially fused with laterotergites on segments II–VIII (suture distinct with light microscope). Two long setae and 1 small and short anterior (on tergum I this seta is more dorsally placed, at the level of the AR) on laterotergites. Terga with approximately 3 rows of setae transversely lined at each side of the midline ( Figs. 6–7 ); 1 small and short seta (3 on tergum I) and 1 pit on AR; 3 short setae and 1 small and short lateral on MR; 3 long setae, 2 shorter setae and 1 pit on PR. Tergum IX ( Fig. 8 ) with 5 setae on PR, including laterotergal setae; PR with second pair from the midline elongate, as long as the last five abdominal segments (caudal setae). Sterna with AR and MR with 2 short setae respectively and PR with 4 longer setae. Segment X membranous, tergum semicircular with 6 small setae transversally lined and 2 slightly bigger setae more dorsal; sternum longitudinally divided into 2 lobes (pygopod), moderately produced.

Figures

FIGURES 9–16. Diaphorocera chrysoprasis, first­instar larva. 9, habitus, dorsal view; 10, habitus, ventral view; 11, head, dorsal view; 12, head, ventral view; 13, left antenna, ventro­lateral view; 14, mouthparts, frontal view; 15, mesothoracic claw, dorsal view; 16, abdominal spiracle I. Scale bars: 500 µm (Figs. 9–10); 100 µm (Figs. 11–12); 20 µm (Figs. 13–15); 5 µm (Fig. 16).

FIGURES 1–4. Diaphorocera chrysoprasis, first instar larva. 1, head, left half, dorsal view; 2, right antenna, dorsal view; 3, left maxilla, ventral view; 4, right mandible, dorsal view. Scale bars: 1 = 0.1 mm; 2–4 = 0.05 mm.

FIGURES 5–8. Diaphorocera chrysoprasis, first instar larva. 5, prothorax, left half, dorsal view; 6, abdominal tergum I, left half, dorsal view; 7, abdominal tergum II, left half, dorsal view; 8, abdominal tergum IX, right half, dorsal view. Scale bar = 0.1 mm.