Paussus kannegieteri

Giulio, Andrea Di, 2008, Fine morphology of the myrmecophilous larva of Paussus kannegieteri (Coleoptera: Carabidae: Paussinae: Paussini), Zootaxa 1741, pp. 37-50 : 39-47

Redescription of Paussus kannegieteri third instar larva

Material examined. Seven third instar larvae, collected together with several pupae and adults from an ant nest of Pheidole plagiaria . Java, Buitenzorg, Pangerango, 15–21.iii.1904, Hjalmar Jensen. This material is preserved in 70% ethanol and is deposited in the Zoological Museum in Copenhagen ( Denmark).

Diagnosis. At present it is not possible to distinguish this larva from the other known larvae of the genus Paussus due to inadequate or incomplete available descriptions.

Measurements. Body length = 9–9.5 mm (from tip of mandibles to the terminal disk); cephalic capsule maximum width (at the base of the antennae) = 1.08 mm, medial length (from occipital foramen to anterior emargination of frontoclypeolabrum) = 0.55 mm, occipital foramen width = 0.72 mm; antennal length = 0.48 mm; mandible length (measured along outer margin) = 0.48 mm, length of prostheca = 0.22 mm; pronotum maximum width = 1.14 mm, maximum length (along ecdysial suture) = 1.4 mm; diameter of terminal disk = 1.92 mm, dorsal plates length (measured along medial suture) = 1 mm, urogomphi (ventral plates) length (measured along medial suture) = 0.84 mm.

Habitus and coloration. Body physogastric with cup-shaped terminal disk ( Figs. 2 , 19 ), held in an elevated position by a thick, swollen abdomen ( Fig. 1 ); cephalic capsule, legs and thoracic tergites shiny, hard and yellowish, weakly sclerotised; thoracic and abdominal segments opaque, soft, pale yellowish-white; ventral edges of parietalia, tentorium, basal parts of frontal sutures, upper part of the occipital foramen, mandibles (especially at apex), medial margin of stipes, spiracles, claws and terminal disk thickly sclerotised and darker coloured.

Microsculpture. Sclerotised parts of the body (e.g. cephalic capsule, mouthparts, thoracic and abdominal tergites, legs, pygidium) smooth or only slightly corrugated. Epipharynx and hypopharynx medially with pointed or multipointed microsculpture, arranged in many parallel, transverse rows; anterior margin of frontal emargination and sides of hypopharynx with tufts of thin elongate sculpticells ( Fig. 9 ). Membranous areas of the body completely covered by a carpet of thorn-like spiniform warts by thin, elongate, filiform apices, shortening towards sclerotised areas ( Figs. 10 , 15–17 ). Surface of the terminal disk with spinulate microsculpture ( Figs. 21, 23 ), composed of conical, pointed sculpticells (average length 4–7 mm, see Fig. 23 ). Pygidium smooth.

Chaetotaxy. Head. Frontal area (laterally including part of parietale) with many (about 60) setae of different sizes, not all symmetrically disposed ( Figs. 3, 5 ); long seta FR2* posterior to FR1*; FR3* elongate, posteromedial; FR4* and FR5* transversally lined (FR4* slightly anterior to FR5*) at base of median emargination; small seta FR6* near and slightly posterior to FR7*; long seta FR7* on anterior margin, forwardly directed; setae FR8*, FR10* FR11* internal to FR7*, lined along anterior margin, bent mediad; pores FR a* FR c* FR d* FR e* present on frontal sclerite, FR b* FR f* absent. Each half of parietal plate ( Figs. 4, 6 ) with about 50 setae, subequally spaced except for a crown o f about 10 setae around the antennal base; basal pores PA m and PA l absent. Antennae ( Figs. 3–7 ): antennomere I with about 15 additional setae, mainly dorsally and laterally, all primary pores present; antennomere II with a crown of 7 additional setae; antennomere III with about 10 additional setae mainly on dorsal side. Mandible ( Figs. 8–9 ) with 2 long additional setae directed mesad; seta MN1 on lateral side, elongate; seta MN2 absent; 6 pores present on each mandible: MN b* and additional pore mesodorsally, MN c* and additional pore more distally, at the base of retinaculum, and MN a* and additional pore lateroventral. Setal group gMX on stipes with few setae (about 6) around base of galea ( MX 4 and MX 5 difficult to identify) and 7 setae along mesodorsal margin; about 10 additional setae present on lateral and ventral sides of stipes (including MX 10); setae MX 2 and MX 3 long; galea with 2 setae at apex, one long, possibly MX 8* displaced apically, and MX 9* small; MX d ventral; MX 7 elongate, at ventral base of galea; maxillary palpomere II (first visible) with lateral additional seta; palpomere III (second visible) with additional lateroventral seta; palpomere IV (third visible, Fig. 12 ) with small additional seta on inner side and longer additional seta on outer side, 2 slender digitiform sensilla subapically and one apical sensorial area with about 10 elongate (about 5µm) subequal papillae (sensilla basiconica); cardo with 3–4 setae; pores MX a and MX c not visible. Dorsal and lateral setae on prementum spiniform, moderately long, ventral setae elongate and curved ( Fig. 11 ); seta LA1 close to midline; LA5 short; LA6 subapical, about as long as palpomere I; 11 pairs of additional setae on prementum: 6 ventral, 1 ventrolateral and 4 dorsal; labial palpomere I with small additional seta ventrolaterally and 2 large additional pores ventrally, obliquely disposed; II with 4 additional setae: 1 short on inner side, 2 on outer side (1 basal spiniform, about as long as internal, and 1 more distal very short), and 1 small ventral and subapical; 2 slender digitiform sensilla subapically and one apical sensorial area with about 7–8 elongate (about 5µm) subequal papillae (sensilla basiconica), similar to those of maxillary palpomere IV. Thorax. Pronotum ( Figs. 13–14 ) with about 40 additional setae on each side of ecdysial suture (primary setae impossible to identify), mainly on anterior and notopleural areas; notopleural setae very long and thin; mesonotum and metanotum ( Figs. 13–14 ) with about 10 additional setae on each side of ecdysial line. Distal leg segment (corresponding to fused coxa, trochanter, femur, tibia and tarsus) with dorsally 6 setae and 2 subapical pores, ventrally and ventrolaterally with a tuft of about 70–80 long and lanceolate setae, with peculiar expanded and flattened apices ( Figs. 17–18 ). Sternal areas of pro-, meso- and metathorax with about 10 pairs of additional setae. Abdomen. Terga of abdominal segments I-VII with about 20 pairs of setae each (identification not possible) and no pores. Dorsal and lateral plates of terminal disk dorsally (tergal side, Fig. 20 ) medially with many short, spiniform, regularly spaced (every 30–50 µm) sensilla S-VII: about 100 on each dorsal, 20 on each lateral plate; ventral plates (urogomphi) each with about 20 setae on ventral side; perimeter of the disk (margin of dorsal, lateral and ventral plates), with a dense fringe of very long hairs ( Figs. 19–21 ); sensilla S-II stick-like with broken apices ( Fig. 21 ), regularly spaced (every 50–70 µm) at margin of plates and urogomphi, radially oriented to the surface of terminal disk: about 15 on each dorsal plate, about 6 on each lateral plate and about 13 on each urogomphus; surface of the terminal disk ( Figs. 21–24 ) with many sensilla S-I of peculiar shape (see next paragraph). Epipleurites of abdominal segment I with 1 or 2 additional setae each; epipleurites of abdominal segments II–VII with 4–6 additional setae each; surface of terminal disk with many pores ( Fig. 23 ) equally spaced every 10–40 µm and spreading evident line of dense substance: about 200 on each dorsal, about 20 on each lateral and about 150 on each ventral plate. Hypopleurites of abdominal segments I–VII with 2–3 additional setae each. Sternal areas with 10–15 setae on each abdominal segment (homologisation not possible). Pygidium without setae.

Head. Cephalic capsule ( Figs. 3–6 ) strongly transverse, about two times as wide as long at middle, prognathous, gradually more curved from sides to base, with maximum width at base of antennae; base of cephalic capsule distinctly convex dorsally, partially retracted into prothorax, without distinct neck region; posteroventral margin with a deep incision at the level of gular suture of parietalia ( Fig. 4 ). Frontoclypeolabrale ( Figs. 3, 5 ) sub-hexagonal: anterior margin not sclerotized, widely emarginated medially; antennal margins anteriorly converging and strongly sclerotised, each as long as half anterior margin; hind margins slightly convergent towards back, and each of about the same size as the anterior margin; basal margin forming the medial part of the occipital margin on the upper surface of the head capsule, well-sclerotised and of about the same size as one of the antennal margins; surface distinctly convex posteriorly and anterolaterally, deeply concave anteromedially; transverse frontal keel absent; coronal suture absent; frontal sutures anteromedially obliterated, basally sclerotized, subparallel and not converging; frontale fused with parietalia. Parietalia ( Figs. 4, 6 ) without stemmata; ventral walls of parietale medially fused into a short gular suture. Each plate dorsally limited by a weakly distinct margin against the hind margin of frontale, and the following well-sclerotised margins: occipital margin, anterior ventral margin against labium and cardo, and lateral margin around mandibular base, forming the globular hollowed-out joint-socket to the globular condyle of the mandible. Antennae ( Figs. 3–4 ) 4-jointed, forwardly directed and slightly convergent anteriorly, slightly overreaching the apices of the mandibles, inserted in voluminous membranous, soft elevations; antennomeres I–III wide, slightly flattened laterally; I asymmetrical, shorter on inner side, about two times as long as wide, about twice as long as II; II short, slightly wider than long; III about two times as long as II; II and IV subequal in length; IV ovoid, very small compared to the others; sensorial appendage ventrolaterally positioned on antennomere III ( Fig. 7 ), conical, more than half length as IV (about 30 µm long and about 20 µm wide at base). Mandibles ( Figs. 8–9 ) slightly falcate, subtriangular, about 1.5 times as long as wide at base, with single, ventral cutting edge; dorsal surface deeply excavate along occlusal margin, ventral surface slightly convex; retinaculum triangular, cuneiform, sharp and pointed, anteriorly directed, displaced apically, forming, together with the pointed apex, a virtually bidentate mandible; posterior edge of retinaculum slightly convex; molar area produced into long, stiff, rather pointed, flat prostheca (possibly movable), with membranous margin on the occlusal side; prosthecae of mandibles crossing above the surface of prementum; penicillus absent. Maxilla with transversal, undivided cardo, subrectangular stipes slightly tapered to apex, 3-jointed palp (first palpomere fused with stipes), 1- jointed galea; lacinia absent; lateral margin of stipes distinctly curved, occlusal margin straight without basal tooth; basal maxillary palpomere wider than long; medial palpomere subquadrate, slightly longer than basal; apical palpomere about as long as basal, but thinner and subulate ( Fig. 12 ). Galea (corresponding to galeomere II of Ozaenini, galeomere I being fused with stipes) digitiform, almost straight, distinctly tapered from base to apex. Labium well-developed, anterior part free, posterior part lying between the cardines of the maxillae; mentum membranous, prementum ventrally sclerotised and palps 2-jointed. Prementum ( Fig. 9 ) short, sclerotised and enlarged from base to apex in ventral view; basal half of prementum dorsally bulging and enlarged, slightly tapering apically; distal half at middle with small subapical ligula, slightly protruding. Labial palpomere I wider and longer than II ( Fig. 11 ); II subulate. Hypopharynx wide and bulged, tongue-like, thick, soft-skinned and densely covered by transverse parallel rows of papillae ( Fig. 11 ), closely fitting in the vault of the oral cavity.

Thorax. Thoracic segments ( Figs. 1 , 13–14 ) slightly sclerotised; tergites, pleura and sternites weakly separated; tergites similar in length, widely transverse with rounded lateral margins, distinctly increasing in width and thickness from pro- to metanotum; surface of tergites irregularly convex ( Figs. 13–14 ); longitudinal ecdysial line restricted to pronotum. Pronotum composed by a single distinct sclerite, concave anteriorly and convex posteriorly, about three times as wide as long. Mesonotum and metanotum, with tergites longitudinally subdivided into two rounded parts, separated and partially embedded into the bulged membranous areas. Sterna of thoracic segments soft, unsclerotised.

Spiracles. Abdominal spiracles ( Fig. 15 ) extremely small, annular-uniforous, dorsolaterally positioned, partially embedded into the bulged membranous areas above the epipleurae on segments I–VIII; peritreme dome-shaped, convex and with a round hole at top; atrium poorly developed; with no trace of closing mechanism. Mesothoracic spiracles annular, similar but slightly larger than abdominal spiracles, with wider atrium. Small spiracle-like structure on metapleura ( Fig. 16 ) corresponding in position to mesothoracic spiracle, but without external peritreme; taenidial annulations present on internal tube but without atrium; connection with tracheal apparatus not visible in the mounted specimen.

Legs. Short but strong, all similar in type and length and directed upwards ( Figs. 1 , 13–14, 17 ); legs 2- joined; first article representing the coxa, basally embedded into soft membranous areas ( Fig. 17 ), dorsally articulated with medially subdivided elongate pleural sclerite; distal part of coxa obliquely truncate to allow the folding of second article. Second article cylindrical, digitiform, composed of completely fused trochanter, femur, tibia and tarsus; sutures between articles not visible. Procoxae slightly more slender than meso- and metacoxae. Tarsus with single small claw ( Fig. 18 ), apically curved and pointed.

Abdomen. Swollen, scarcely or not sclerotised distinctly curved in a strongly upturned position ( Fig. 1 ); largest width and thickness at segments III and IV, gradually narrowed towards both ends; segments I–VII thick, with terga flattened or slightly convex, pleura and sterna extremely swelling; terga, pleura and sterna strongly marked against each other like swollen membranous pillows; pleurae rather grooved where lateral abdominal muscles are attached. Terminal disk ( Figs. 2 , 19–21 ) regularly round, flat or slightly concave at middle, with perimeter strongly raised, corrugated and markedly sclerotized; with diameter slightly smaller than segment VII, composed of 6 symmetrical subtriangular plates, joined by thin membranous lines; dorsal plates slightly wider than others, lateral plates small; ventral plates corresponding to modified urogomphi. Pygidium cylindrical, dorso-ventrally flattened, ventrally positioned to urogomphi.

Sensilla S-I ( Figs. 21–24 ). Sensilla inserted perpendicularly to the surface of terminal disk ( Fig. 21 ), composed by an elongate basal stem (20–40 µm) laterally and/or apically multilobed and multispinulate, and a short, stick like smooth seta (8–15 µm), often clavate and apically truncate and fringed, medially emerging from a dome-like apex. Two main types of sensilla S-I are present on terminal disk: (a) those present only along the raised margin (about 25 along each dorsal, about 10 along each lateral, and about 20 along each ventral plate), characterised by basal stem laterally and subapically produced into 9–13 flattened, hand-like, multispinulate ridges ( Fig. 22 ); (b) those covering the surface of terminal disk ( Figs. 21, 23–24 ), regularly spaced every 60–70 µm (about 100 on each dorsal plate, 10 on each lateral plate, and 70 on each ventral plate), characterised by cylindrical basal stem covered by spinulate microsculpture, similar to that covering the surface of terminal disk, and with radially multilobed, star-like apex (diameter 40–60 µm); each radial lobe cylindrical and apically produced into 5–8 large conical thorns surrounded by variable number of small spines.

Figures

FIGURES 1 – 2. Paussus kannegieteri third instar larva: 1, habitus, lateral view (from Bøving 1907); 2, terminal disk, apical view. Scale bars: Fig. 1 = 1 mm; Fig. 2 = 0.5 mm.

FIGURES 19 – 24. Paussus kannegieteri third instar larva: 19, terminal disk, apical view; 20, terminal disk, dorsal view; 21, left dorsal plate of terminal disk, dorsolateral view; 22, sensillum S-I on margin of terminal disk; 23, sensillum S-I on surface of dorsal plates, lateral view; 24, sensillum S-I on surface of ventral plates, apical view. aml = apical multispinulate lobe of sensillum S-I, bs = basal stem of sensillum S-I, dp = dorsal plate, ep = epipleurite, lmr = lateral multispinulate ridge of sensillum S-I, lp = lateral plate, po = pore, py = pygidium, t = tergum, S-I = sensillum S-I, S-II = sensillum S-II, se = seta of sensillum S-I, ug = urogomphus; the arrows indicate the substance coming out from pores. Scale bars: Figs. 19 – 20 = 250 µm; Fig. 21 = 200 µm; Figs. 22, 24 = 10 µm; Fig. 23 = 20 µm.

FIGURES 7 – 12. Paussus kannegieteri third instar larva: 7, apex of left antenna, ventral view, details of antennomere IV and sensorial appendage; 8, left mandible, dorsal view; 9, detail of mouthparts, frontal view; 10, intersegmental membrane between head (down) and prothorax (up), dorsal view; 11, labial palpomeres, ventral view; 12, right maxillary palpomere, anterior view. ds = digitiform sensillum, FR = frontoclypeolabrale, hv = hyaline vescicle, LA = labium, m = membrane, MN = mandible, PR = pronotum, pt = prostheca, re = retinaculum, sa = apical sensorial area. Scale bars: Figs. 7, 12 = 20 µm; Figs. 8 – 9 = 100 µm; Figs. 10 – 11 = 50 µm.

FIGURES 13 – 18. Paussus kannegieteri third instar larva: 13, thorax, left lateral view; 14, thorax, dorsal view; 15, mesothoracic spiracle; 16, metathoracic spiracle-like structure; 17, mesothoracic leg, anterolateral view; 18, apex of metathoracic leg with lanceolate setae, posterolateral view. CO = coxa, ls = lanceolate setae, m = membrane, ME = mesonotum, MT = metanotum, pe = peritreme, PR = pronotum, un = claw. Scale bars: Figs. 13 – 14 = 500 µm; Fig. 15 = 10 µm; Fig. 16 = 20 µm; Fig. 17 = 200 µm; Fig. 18 = 50 µm.

FIGURES 3 – 6. Paussus kannegieteri third instar larva: 3, head, dorsal view; 4, head, ventral view; 5, head, frontal view; 6 head, left lateral view. FR = frontoclypeolabrale, PA = parietal plate. Scale bars: 3 – 6 = 200 µm.