Silphinae Latreille, 1806
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publication ID |
https://doi.org/10.1590/1806-9665-RBENT-2025-0014 |
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persistent identifier |
https://treatment.plazi.org/id/FD2D8785-FF8A-FFA4-FCE0-C05EFC9BF97A |
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treatment provided by |
Felipe |
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scientific name |
Silphinae Latreille, 1806 |
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Subfamily Silphinae Latreille, 1806 View in CoL
Genus Oxelytrum Gistel, 1848
Oxelytrum cayennense (Sturm, 1826)
Eggs (n = 77)
( Figs. 2A–D View Figure 2 )
Maximum width: 1.00 – 1.82 mm (mean 1.33 mm). Eggs laid individually or in clusters on the soil surface, in variable quantities (31.44 ± 26.7 eggs); protected by a thin transparent membrane ( Figs. 2A and B View Figure 2 ). Eggs are oval-shaped, varying from white to yellowish white chorion with wrinkled carvings ( Figs. 2C and D View Figure 2 ); micropyle not visualized.
First instar (L1) larva (n = 41)
( Figs. 3A–C View Figure 3 , 4A–G View Figure 4 , 5 A–B View Figure 5 , 6 View Figure 6 , 7 View Figure 7 and 8 A–B View Figure 8 )
Body length: 5.09 – 8.87 mm (mean 7.24 mm); head width (between dorsal stemmata): 0.76 – 1.44 mm (mean 1.13 mm); pronotum width: 2.10 – 3.68 mm (mean 2.67 mm). Campodeiform, narrowing towards both ends, widest at metathorax, flattened dorsoventrally. General color: dorsal region predominantly brown, lateral expansions varying from white to light yellow, each one bearing a posterolateral seta; medial line thin and yellow on thoracic terga ( Fig. 3A View Figure 3 ); ventrally, thorax predominantly membranous and white; abdominal sterna brown, shade slightly lighter than that of terga ( Figs. 3B and C View Figure 3 ). Dorsal and ventral surfaces dull. Terga with regular isodiametric microsculpture on posterior margin, except absent in nineth segment and the pronotum with microsculpture on anterior and posterior margin.
Head capsule. Prognathous, narrower than the pronotum, dark brown, heavily sclerotized. Coronal suture short; frontal branches in an open-U shape, extending until inner lateral margin of antenna sockets; epistomal suture interrupted at medial region ( Fig. 4A View Figure 4 ). Three pairs of stemmata on each side: two dorsal pairs above antennal level, one pair below antennal level ( Fig. 4B View Figure 4 ). Three antennomeres ( Figs. 3A, B View Figure 3 , 4B, D, E and G View Figure 4 ), first antennomere wider and slightly shorter than others, bearing many small setae; second antennomere narrower at the base with three subapical setae ( Figs. 4A View Figure 4 : A1, A2, A3) and inner lateral lobe with small sensillar cone (arrow in Fig. 4G View Figure 4 ); third antennomere white, narrower than others, with many setae ( Figs. 3A, B View Figure 3 and 4G View Figure 4 ) and three microchaetae at apex ( Fig. 4F View Figure 4 ). Clypeus sub-trapezoidal, short, with four pairs of setae ( Fig. 4A View Figure 4 ): one anterior pair (C1), one anterolateral pair (C2), one lateral pair (C3) and one pair on medial region (C4). Labrum free, sub-rectangular, formed by three distinct sclerites; medial anterior sclerites larger than others, bearing two pairs of setae, one internal and short (Lb1) and one anterolateral long (Lb2) ( Fig. 4A View Figure 4 ); medial posterior sclerite bifid, without setae and a lateral sclerites with one pair of setae each, internal setae (Lb3) longer than external (Lb4) ( Fig.4A View Figure 4 ). Mandible strong, prominent, mobile, sub-symmetrical, apex bifurcate, apical tooth about 2X longer than sub-apical tooth,
inner margin of apical tooth with nine denticuli ( Fig. 4C View Figure 4 ), with one pair of setae arising from each side ( Fig. 4A View Figure 4 ): one anterolateral and short (M1), one internal and long (M2), inner margin of sub-apical tooth without denticuli. Maxilla ( Fig. 5 View Figure 5 ) mobile, cardo (CA) broad, with one lateral seta near apex (arrow); stipes (ST) as long as wide, tapering apically, with four setae in outer margin, one in inner margin and one pore in inner margin; lacinia and galea basally fused, separated only apically. Galea (GL) with sclerotized base, apex membranous, sub-rounded with several brush-like setae; lacinia with nine spike-like setae on inner lateral surface, elongate apically, apex shorter than galea. Maxillary and labial palpomeres without basiconical sensillae at apex; maxillary palpomeres (MP) trimerous, first segment as long as second, which bears three setae, third segment slenderer, longer than second, tapering distally, covered with several minute setae. Labium, submentum (SM) and mentum (ME) fused, submentum tapering gradually towards apex, less sclerotized in distal and basolateral regions, with setae of different lengths and one pore on each side at mid-length (arrow in Fig. 5 View Figure 5 ); mentum sub-rectangular, about 2X wider than long, wider than base of prementum (PME), more sclerotized at the base, with one pair of long setae at mid-length, one basal pair shorter, clearly more inconspicuous – and one pore located laterally between shorter and longer setae (arrow in Fig. 5 View Figure 5 ); prementum short and bearing one setae on each side near apex (arrow in Fig. 5 View Figure 5 ). Labial palpomeres (LP) dimerous, distal segment conical, narrower and greatly shorter than proximal, about half length of basal segment, bearing basiconical sensillae in distal region ( Figs. 5 View Figure 5 , 6 View Figure 6 ). Ligula (LG) bilobed, heart-shaped and membranous, covered ventrally by fine short setation on the two lobes ( Fig. 5 View Figure 5 ). Epipharynx with one pair of anterolateral spine-like setae, below of labial palp (SS, Fig. 6 View Figure 6 ) and one pair of anteromedial spatula-shaped setae; two pairs of medial pores, two longitudinal areas covered by microchaetae; gula and gular sutures absent.
Thorax, pronotum narrower but longer than meso- and metanotum ( Fig. 3A View Figure 3 ). Pleuron with one elliptical spiracle on intersegment of mesothorax (arrow in Fig. 3C View Figure 3 ), twice length of abdominal spiracles ( Fig. 3C View Figure 3 ). Prosternum ( Figs. 3B View Figure 3 and 4E View Figure 4 ) with three small and sclerotized plates on anterior region, medial plate trapezoid -shape, larger than others, lateral plates subtriangular; intercoxal region with several short setae. Legs ( Fig. 7 View Figure 7 ) pentamerous, diameter decreasing towards apex; femora and tibiae longer than other segments; coxae, trochanters, femora and tibiae bearing bunches of setae; trochanters and femora with two ventral rows of short and strong spines; a single seta longer than spikes between rows, at mid-length; tarsungulus with one pair of setae ( Fig. 7 View Figure 7 ).
Abdomen ( Figs. 3A and B View Figure 3 ) with 10 segments visible in dorsal view, tapering towards apex, with lateral expansions projecting posteriorly in distal segments. Terga 1–9 light brown, brown shade, becoming lighter towards distal region. Sternum 1 divided into three weakly sclerotized sternites, one medial and two lateral. Sternum 2 with three sclerotized sternites, one medial sternite larger than two lateral combined (described above). Sterna 3–8 large and highly sclerotized, not reaching terga. Abdominal pleura 1–8 containing a rounded spiracle each ( Fig. 3C View Figure 3 ). Segment 9 with a pair of apical dimerous urogomphi, basal segment wider, light brown and 1.5x longer than distal one (arrow in Fig. 8 View Figure 8 ), bearing 4–5 setae distally. Sternum 9 joint with respective tergum laterally ( Fig. 3C View Figure 3 ). Segment 10 tubular without lateral projections, with a circular anal opening (arrow in Fig. 8A View Figure 8 ), several setae arising from segment apex, a pair of longer setae dorsally located (arrow inFig. 8B). All sternites with a row of setae in posterior margin.
Second instar (L2) larva of Oxelytrum cayennense (n = 51)
( Figs. 9A–C View Figure 9 and 10A–D View Figure 10 )
Body length: 8.72 – 14.78 mm (mean 10.64 mm); head width (between dorsal stemmata): 1.06 – 1.79 mm (mean 1.37 mm); pronotum width: 3.01 – 3.89 mm (mean 3.38 mm). General color: dorsal region predominantly light brown, with a pale medial line, extending to the last abdomen segment, becoming evanescent towards the last tergite, more evident than L1. Lateral expansions present, increased compared to L1, varying from white to light yellow ( Fig. 9A View Figure 9 ); Head light brown; tergites 1-9 light yellow with lateral whitish; maxillary and labial palpomeres with basiconical sensillae at apex ( Figs. 10A–C View Figure 10 ). A pair of micro setae between dorsal stemmata ( Fig. 10D View Figure 10 ). Basal segment of urogomphus light brown, approximately three times as long as distal. Remaining characters as in L1.
Third instar (L3) larva of Oxelytrum cayennense (n = 32)
( Figs. 11A–C View Figure 11 , 12A–D View Figure 12 and 13A–F View Figure 13 )
L3 ( Figs. 11 View Figure 11 , 12 View Figure 12 and 13 View Figure 13 ). Body length: 19.0 – 22.6 mm (mean 16.70 mm); head width (between dorsal stemmata): 1.03 – 2.55 mm (mean 1.98 mm); pronotum width: 4.00 – 5.00 mm (mean 4.53 mm). General color: dorsal region predominantly dark brown ( Figs. 11A and C View Figure 11 ), with lateral expansions increased compared to L2, varying from white to light yellow only on the anterolateral half; sometimes yellow colored on head ( Fig. 12A View Figure 12 ) and on segments 9 and 10; a longitudinal medial yellowish line extending from pronotum to tergum 9, wider than in previous instars ( Fig. 11A View Figure 11 ). Maxillary and labial palpomeres without basiconical sensillae at apex; Labial palpomeres dimerous and maxillary palpomeres trimerous ( Fig. 12B View Figure 12 ). Prosternum sclerotized, meso- and metasternum with sclerotized punctures ( Fig. 11B View Figure 11 ). Thoracic spiracle elliptical ( Fig. 13B View Figure 13 ), about twice as large as rounded abdominal spiracles ( Fig. 13E View Figure 13 ). Abdominal sterna yellowish-brown with conspicuous sclerotized punctures ( Fig. 11B View Figure 11 ). Urogomphi with proximal segment dark brown, three times as long as distal one ( Fig. 12C and D View Figure 12 ). Segment 10 bearing spine-like setae, dorsal pair distinctively longer ( Fig. 13F View Figure 13 ). Characteristics observed through SEM, only observed in L3: Thoracic and abdominal terga with setae short on lateral margin ( Fig. 13C and D View Figure 13 ); abdominal sterna with several short slender setae ( Figs. 13C and D View Figure 13 ). Remaining characters as in L1 and L2.
Pupa of Oxelytrum cayennense (n = 16)
( Figs. 14A–C View Figure 14 , 15A–F View Figure 15 and 16A–F View Figure 16 )
Body length: 13.0 – 20.0 mm (mean 16.5 mm). Adectica exarate, white-colored ( Fig. 14A–C View Figure 14 ). Pronotum: width= 4 – 6 mm, wider than other tergites; four long plain setae on anterior margin ( Fig. 14B View Figure 14 and 15A View Figure 15 ); short setae conglobate on lateral margin; fewer setae on posterior region ( Fig. 14A View Figure 14 ); tergites 1-2 with anterior and posterior wings, respectively. Abdomen: Segments 2–8 each with a pair of long, lateral setae ( Fig. 15E View Figure 15 ), about 2.12 mm long; segment 9 with a pair of urogomphi ( Fig. 16F View Figure 16 ), as long as abdominal setae; segment 10 with a pair of short setae ( Fig. 16F View Figure 16 ). Pleura, abdominal segments 1 – 5 ( Fig. 14A View Figure 14 ) with a pair of functional spiracles ringshaped, anterior-most four heavily sclerotized; segments 6 – 8 with vestigial spiracles; segments 1 – 3 bearing dorsolateral sclerotized regions, rounded, which are more sclerotized on segment 1 and 2 ( Fig. 14C View Figure 14 ).
Remarks: In general, the characteristics that vary between the larval stages of O. cayennense are related to coloration, urogomphi and body length ( Fig. 17 View Figure 17 ). The lateral expansions are whitish in the first and second instar ( Fig. 17E and F View Figure 17 ), while the third instar is whitish only in an interior margin, posterior margin brown ( Fig. 17G View Figure 17 ). The medial line is thin, conspicuous only in the thoracic segments in the first instar ( Fig. 17E View Figure 17 ), in second instar is thin, conspicuous in all body segments ( Fig. 17F View Figure 17 ), while in third instar is wide and conspicuous in all body segments ( Fig. 17G View Figure 17 ). The head color is dark brown in the first instar ( Fig. 17A and E View Figure 17 ), light brown in second instar ( Fig. 17B and F View Figure 17 ) and yellow in third instar ( Fig. 17C and G View Figure 17 ). The basal segment of urogomphus is light brown and 1.5 x longer than distal one in first instar, in second instar the basal segment is light brown and 3 x longer than distal, while in third instar is dark brown and 3 x longer than distal segment. The body measurement varies between the instars: in first instar varies 5.09 – 8.87 mm, in second instar varies 8.72 – 14.78 mm and in third instar varies 19.00 – 22.6 mm. The pupa ( Figs. 17D and H View Figure 17 ) presents adult structures perceptible in pharate imago: compound eyes and clavate antennae ( Figs. 14A View Figure 14 and 16B View Figure 16 ), wings ( Figs. 14A View Figure 14 and 15D View Figure 15 ), legs with pentamerous tarsi and tarsal claws ( Figs. 14A View Figure 14 and 16D View Figure 16 ). Analyzing the pupae of O. cayennense and O. discicolle it is possible to notice some changes in relation to the larval stage, such as: differences in color, since the pupae has a light color, from yellow to whitish, while the larvae are light to dark brown; it is possible to observe structures in the pupae that belong to the pharate adult, such as the formation of two extensions on the thorax that correspond to the wings, in addition to the modification in the tarsomeres, which in the adult are divided into five segments. Despite the similarities, the pupa of O. discicolle differs from O. cayennense by the remake in the outer bristle of the anterior region of the pronotum, which is bifid at the apex, while in O. cayennense the bristles are plain.
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