Planiplax sanguiniventris (Calvert, 1907)

Novelo-Gutiérrez, Rodolfo, 2021, Description of the larva of Planiplax sanguiniventris (Calvert, 1907) (Odonata Libellulidae), Zootaxa 4966 (5), pp. 578-584 : 579-584

Planiplax sanguiniventris (Calvert, 1907)

( Figs. 1–5 )

Material studied: 1 F-0 larva. MEXICO: Tabasco; Municipality of Tenosique, Laguna Canitzán Punta “Los Ángeles” (17.5854°N, 91.3893°W), elevation 5 m, 18 August 2015, A. Mayorga leg.

Description. Larva pale dorsally with abundant light-brown spots and dots ( Fig. 1a ), pale ventrally ( Fig. 1b ), body robust and moderately hairy, legs hairy, abdomen with dorsal protuberances on S3–9 and posterolateral spines on S8–9, caudal appendages sharply pointed.

Head ( Fig. 2a ). Small relative to rest of body, subrectangular, 1.4x as wide as long, wider than prothorax. Labrum pale, bordered with brown, with a small central brown spot on pale area, anterior margin setose. Clypeus pale, bare, with two large, subrectangular, light brown spots close to anterior margin of anteclypeus. Frons pale, mostly bare, anterior border with abundant long, whitish setae directed forward, dorsal surface with short dark, stiff and erect setae; vertex mound-like, pale, encircled by brown, ocelli large and pale. Antenna 7-segmented, scape cylindrical, pedicel barrel-shaped, scape mostly yellowish-brown, pedicel and flagellomeres creamy pale ( Fig. 2b ), scape and pedicel with short whitish stiff setae, flagellomeres with sparse, short, and long delicate setae, 3rd and 6th antennomeres the longest, 4th and 5th antennomeres the shortest, size proportions: 0.6, 0.6, 1.0, 0.5, 0.5, 1.0, 0.8. Compound eyes relatively small, anterolateral, and protruding dorsally ( Figs. 2b, c ); posterolateral margins of head behind eyes bulging. Occiput large, cephalic lobes bulging, with longitudinal rows of small spiniform setae and sparse stiff long setae ( Figs. 2a, c ); occipital margin concave. Mandibles ( Fig. 2d, e ) without molar crest, with formula: L 1234 0 a b / R 1234 y a b d, b>a in left mandible b>d>a in right mandible; both mandibles with a large, dark, laterobasal spot. Maxilla: galeolacinia with seven teeth, three dorsal teeth almost straight, of similar length but basal one more slender, four ventral teeth of different size and robustness, basal tooth shortest, apical one largest, maxillary palp a little shorter than galeolacinia, ending in a robust blunt spine. Ventral pad of hypopharynx transversally enlarged ( Fig. 2f ), anterior margin convex with abundant long setae, posterior margin concave with a row of stiff setae directed apically. Labium scoop-shaped; prementum-postmentum articulation surpassing posterior margin of procoxae. Prementum subrhomboidal ( Figs. 3a, b ), 1.2x as wide as long, lateral margins smooth, widely divergent apically; large premental setae 6–7 ( Fig. 3b ), additional smaller setae 3−4 on each side of midline; a row of 4–5 short spiniform setae at the base of palp articulation; ligula moderately developed, anterior margin finely crenulate ( Figs. 3a, b ), the medial apex convex, sides straight, a submarginal row of 6−7 small stout spiniform setae to each side of tip. Labial palpi strongly developed, covering inferior part of face as a mask ( Figs. 2 a-c), each with 8–9 strong crenations on apical margin, each crenation finely serrulate with one short stout seta per crenation ( Figs. 3a, b ); seven palpal setae on dorsal margin ( Fig. 3b ), ventral margin almost straight, serrulate, with a row of six regularly spaced robust setae which increase in size distally; external surface of palp spotted ( Fig. 3a ), internal surface with 2–3 minute spiniform setae close to palpal base; movable hook long and slender, as long as contiguous seta, sharply pointed and smooth. Ventral surface of prementum ( Fig. 3a ) covered with sparse delicate hair-like setae and minute spiniform setae.

Thorax. Pronotum wider than long, with a complex color pattern of creamy pale and brown irregular spots ( Figs. 1a , 2a ); anterior margin of pronotal disc nearly straight, recurved, and thickened at sides, posterior margin very thick, recurved ( Figs. 2b, c ), lateral margin convex, all margins with short white delicate setae; a large, subrectangular bare area on each side of midline ( Fig. 2a ); inferior margin of propleura broadly rounded with tufts of long stiff white setae. Mesospiracle partially hidden ( Figs. 1a , 2a ). Side of pterothorax sloping down more or less steeply, mostly pale with a wide brown stripe along the meso- and metapleural sutures ( Fig. 2c ), most of lateral surface with long delicate white setae. Legs setose, very long (e.g., when fully extended, tip of metatibia surpasses tip of abdomen) ( Fig. 1 ); coxa and trochanter creamy pale, femur pale with two dark bands, tibia pale with one dark band, tarsi mostly light brown with tips pale; dorsal and lateral surfaces of meso- and metafemora with abundant minute spiniform setae; distal third of pro- and mesotibiae and distal half of metatibiae with abundant bi-, tri-, and tetradentate setae on internal (posterior) surface ( Fig. 3c ); ventral surface of all tarsi with two rows of setae as follows: protarsomeres with an external row of tridentate setae, the mesal row with stout spiniform setae; ventral surface of meso- and metatarsomeres with strong spiniform setae in both rows ( Fig. 3d ); pretarsal claws simple, slender, and very long: 0.63, 1.0, and 0.8 the length of distal tarsomere on pro-, meso-, and metatarsi, respectively, all with pulvilliform empodium. Anterior and posterior wing sheaths slightly divergent ( Fig. 1a ), reaching basal half and posterior margin of S6, respectively, both pairs setose mainly on borders.

Abdomen. Oblong, 1.3x longer than wide ( Fig. 1 ), reaching its maximum width at S6, abruptly tapered, with S10 reduced and sunken into S9. Tergum pale with abundant brown spots and dots arranged in a complex pattern ( Figs. 1a , 4 ). Tergites with abundant minute spiniform setae including posterior margins; dorsal protuberances on S3–9 ( Fig. 4a ), vertical on S3, directed posteriorly on S4–9, thick and bluntly-pointed on S3–6, ending in an acute spine on S7–9 ( Fig. 4 ), dorsal margin of protuberances on S5–6 straight and parallel to abdominal tergum, all protuberances with abundant small spiniform setae and hair-like setae; lateral margins of S4–9 beset with small, closelyset spiniform setae, intermingled with long white setae; lateral spines on S8–9 large and sharply pointed ( Fig. 4b ), those of S8 slightly divergent, those of S9 longer, surpassing tips of cerci, more or less straight and parallel, 0.6 and 1.0x the middorsal length of their respective segments. Sternum creamy pale ( Fig. 1b ), with a slight yellow tint on sterna 8–10, a pair of submedian light brown spots on sterna 5–8; posterior margins of sterna 1–5 smooth, 6–10 with a row of spiniform setae which increase in size and robustness caudally; sternum 9 with a subapical group of long white bristle-like setae on each side of midline; sterna 3–5 and 8–9 divided into five sternites, sterna 2 and 6–7 divided into three sternites, that of 10 forming a continuous ring with respective tergum; sutures slightly divergent on 3–4, slightly convergent caudally on 5–6, and parallel on 7–9. Gonapophyses lacking. Caudal appendages ( Fig. 4b ) pyramidal, long (e.g., epiproct and paraprocts as long as or longer than dorsal length of S9+10), sharply pointed. Epiproct longest, cerci shortest, 0.6x the length of epiproct; epiproct with a row of spiniform setae intermingled with long bristle-like setae on lateroventral margins; cercus with small white setae on dorsal surface; paraproct with a row of stout spiniform setae intermingled with bristle-like setae on dorsal and ventral borders.

Measurements: TL 18; AL (ventral, incl. app) 11; MWa 7.2; MWh 4.2; HfL (lateral) 6.5; Ep 1.7; Pp 1.5; Ce 0.9.

Diagnosis. The larva of P. sanguiniventris can be separated from that of P. phoenicura by the following features (features of P. phoenicura in parentheses): left mandible lacking tooth ‘d’ (with tooth ‘d’); right mandible lacking tooth ‘c’ (with tooth ‘c’); premental setae 10 on each side of prementum midline (premental setae 6−7); ligula with a submarginal row of four minute spiniform setae on each side of medial projection, apex lacking setae (11 minute setae plus 2 setae on apex); 7 palpal setae (5 palpal setae); dorsal protuberance on S3 higher than that on S4 (noticeably lower), dorsal protuberances on S3−6 thick, bluntly-pointed (slender and sharply-pointed); lateral spines on S8 slightly divergent (convergent); lateral spines on S9 straight (incurved), and caudal appendages longer than in P. phoenicura . In the same manner, the larva of P. sanguiniventris can be separated from the unidentified congeneric larva from Colombia ( Tennessen 2019) by the following features (features of Planiplax sp. in parentheses): premental setae per side 10 (6−7); 7 palpal setae (5); dorsal protuberance on S3 well developed (lacking); dorsal protuberances on S4−5 thick, bluntly-pointed, and pointing directly posteriorly, dorsal margin of protuberance on S5 straight and parallel to abdominal tergum (slender, sharply-pointed, and pointing up and posteriorly, dorsal margin of protuberance on S5 convex and not parallel to abdominal tergum). A provisional summary of the major generic characters of Planiplax based on the 3 species now known are: head relatively small with eyes protruding prominently, 5–7 palpal setae, 6–10 premental setae, crenations on distal margin of labial palp well-developed, each crenation bearing one stout spiniform setae, anterior and posterior margins of pronotum thick, hind tibiae slender, straight, and noticeably long, dorsal hooks on S3–9 or S4–9, posterolateral spines on S8–9 long, S10 sunken in S9, caudal appendages long and sharply pointed. Only a handful of genera of Libellulidae inhabiting the New World share with Planiplax the compound eyes small and protruding dorsally of which Planiplax differ by the following features (other genera in parentheses): distal margin of prementum slightly concave or straight and finely serrulate (convex and crenulate Ladona Needham, 1897 , Orthemis Hagen, 1861 , Plathemis Hagen, 1861 ); median lobe of ligula not raised (raised, Cannaphila Kirby, 1889 , Libellula Linnaeus, 1758 [ Tennessen 2019]); posterolateral spines on S9 as long as S9 dorsal length (shorter, all other five genera); hind legs long, tibiae extending well beyond caudal appendages (shorter, hind tibiae not surpassing caudal appendages Libellula , Ladona , Orthemis , Plathemis ); hind tibiae slender and straight (thicker and slightly bowed, all other five genera); middorsal protuberances on S3–9 or S4–9 (lacking at all in Cannaphila and Orthemis , and in some Libellula species , when present in Libellula always lacking on S9; on S4–7 Ladona , on S3–6 or S4–5 Plathemis [ Tennessen 2019]).

Habitat. The area surrounding the Canitzán lagoon has been reported as impacted by human activities such as agriculture, livestock, and human settlements. The vegetation present in the lagoon is a mixture of Phragmites sp. (Poaceae) , Typha sp. (Typhaceae) , and Thalia sp. (Marantaceae) , as well as floating Eichhornia sp. (Pontederiaceae) , and Salvinia auriculata Aubl. (Salviniaceae) ( Castillo et al. 2018). I have seen adults of P. sanguiniventris in Veracruz State flying and ovipositing in lagoons and large ponds covered with aquatic macrophytes such as Nymphaea sp. (Nymphaeaceae) ( Fig. 5a ), Nymphoides indica (L.) ( Menyanthaceae ) ( Fig. 5b ), Eichhornia crassipes (Mart.) and Pistia stratiotes L. ( Araceae ) ( Fig. 5a ). However, the presence of “dark mud and silt on the dorsum of the head, the thorax and coxae, the wing sheaths and also some on the dorsum of the abdomen indicates that this species wallows in substrate rather than clinging to stems or other supports above the substrate” (Tennessen, pers. comm.).

Figures

FIGURE 1. Planiplax sanguiniventris, habitus F-0 larva. a) dorsal, b) ventral.

FIGURE 2. Planiplax sanguiniventris details of larval morphology. a) Head and pronotum, dorsal view; b) ídem, right lateral view; c) head and thorax, oblique view; d) right mandible, ventrointernal view; e) left mandible, internal view; f) hypopharynx, ventral view.

FIGURE 3. Planiplax sanguiniventris details of larval morphology. a) Prementum, ventral view; b) ídem, dorsal view; c) right mesotibia, ventral view; d) mesotarsomeres, lateroventral view.

FIGURE 4. Planiplax sanguiniventris details of larval morphology. a) Dorsal protuberances on S3−9, laterodorsal view; b) S8−10 and caudal appendages.

FIGURE 5. Typical habitats where adults of Planiplax sanguiniventris have been observed flying and ovipositing in Veracruz State: a) Cansaburros wetland covered with aquatic macrophytes Nymphaea sp. (Nymphaeaceae) and Pistia stratiotes L.(Araceae); b) Laguna Miradores with patches of Nymphoides indica (L.) (Menyanthaceae).