Hybosa acutangula Spaeth, 1913

Świętojańska, Jolanta & Linzmeier, Adelita M., 2024, Description of immature stages of Hybosa acutangula Spaeth, 1913 (Coleoptera, Chrysomelidae, Cassidinae), Zootaxa 5519 (3), pp. 395-422 : 397-417

Hybosa acutangula Spaeth, 1913

Egg

( Figs 2–4 )

Measurements (n = 5 [mm]). Mean length of egg: 1.38; width: 0.89 ( Table 1 ). Flat, elongated, integument slightly granulated, light brown; covered by a transparent mass placing them together and overlapping. Egg mass covered by a dark faecal shield, mostly rounded, measuring 5.6 mm x 4.7 mm (mean, n = 3).

First instar larva

( Figs 11–43 )

Measurements (n = 7 [mm]): length of body: 0.85–1.30; width of body: 0.55–0.60; length of supra-anal processes: 0.75–0.87; width of head: 0.40–0.42 ( Table 1 ). Length of body was measured without head, from anterior border of pronotum to the base of supra-anal processes; width of body was measured across metathorax without lateral scoli.

Body dorso-ventrally flattened, elongate-oval, narrowed posteriorly, widest across meso- and metathorax ( Fig. 11 ). Larvae preserved in alcohol light yellow with a brown head and two brown spots on the pronotum, light brown supra-anal processes and legs.

Lateral scoli of fourth pair reduced thus body is with 15 pairs of scoli and a pair of supra-anal processes; additional distinct tubercles (which look like very short lateral scoli) apically armed with single seta is placed between scoli of second and third pair ( Figs 11 , 12 , 26, 27 ). Scoli of thorax, of posterior pair on meso- and metathorax, and of last pair on abdomen the longest, slightly longer than half width of body. Remaining lateral scoli shorter, more or less of the same length, their length is as half length of the longest scoli. All lateral scoli apically armed with long seta ( Figs 28, 29 ), each apical seta is as long as length of scoli on which seta is located; scoli without lateral branches but with a few setae (usually 2–4) on sides ( Figs 24, 25 ). Supra-anal processes as long as length of abdomen, bent dorsally, basally covered with asperities then with spines, apexes rounded without apical setae ( Figs 11 , 34–36 ).

Anal turret distinct and 2-segmented ( Figs 11–13 ).

Nine pairs of spiracles (one on thorax and eight on abdomen), each distinctly elevated, and visible from dorsal view ( Figs 11 , 12 , 31, 33 ).

Body distinctly granulated ( Fig. 11 ). Minute setae at anterior border of tergites and sternites; tergites and sternites with setae. Setae of tergites short, setae of sternites very long in comparison to setae of tergites. Setae of head and legs of the same type as of body ( Figs 11–15 , 23 , 37–40 ).

Each side of pronotum with ten setae; single campaniform sensillum on each anterior side, close to body axis ( Fig. 12 ). Anterior border of meso- and metanotum with a pair of minute setae placed medially and two minute setae on each side laterally. Meso- and metanotum also with two rows of setae running along width of tergite: first with two setae placed antero-medially, and second with ten setae placed posteriorly; three setae on each antero-lateral side. Anterior border of abdominal tergite I with a pair of minute setae placed medially and two minute setae on each side laterally. Abdominal tergites II–VIII with a pair of minute setae at anterior border medially and single minute seta on each side laterally. One minute seta and one long seta close to each abdominal spiracle. Abdominal tergite I also with two rows of long setae running along width: with six setae placed anteriorly and second with four setae placed postero-medially. Abdominal tergites II–VIII on each side with a pair of long setae placed on each antero-lateral side and with row of four long setae placed postero-medially.

Anterior border of pro-, meso- and metasternum with two minute setae ( Fig. 13 ). Two minute setae at base of each leg. Two pairs of pointed setae in the middle of pro-, meso and metasternum. Anterior margin of all abdominal sternites with one pair of minute setae placed medially. Moreover, abdominal sternites I–IV with eight long, pointed setae placed medially and two setae on each postero-lateral side. Abdominal sternite V with six long, pointed setae placed medially and two setae on each postero-lateral. Abdominal sternites VI–VII with four long, pointed setae placed medially and two setae on each postero-lateral side. Abdominal sternite VIII with four setae in the middle of segment. Single seta at base of each abdominal lateral scoli.

Head well sclerotized, hypognathous, retracted into pronotum. Median suture complete, connected with frontoclypeal suture ( Figs 14, 15 , 37–40 ). Clypeus distinct, wider than long, with one pair of setae and one pair of campaniform sensilla ( Fig. 14 ). Six distinct stemmata on each side of head ( Figs 38, 40 ).

Head on each side with four small, vertical, pointed setae (V 1–4; Figs 14 , 37, 41 ), and five frontal rows of long setae: row Fa with three setae, Fb with five setae, Fc with three (sometimes four—doubled Fc2) setae, Fd with single seta, Fe with two setae ( Fig. 14 ). Temporal surface of head with three setae ( Fig. 15 ).

Antennae 2-segmented, set in membranous ring ( Figs 22 , 38, 43 ). Both antennomeres stout but first is wider than long, and the second longer than wide. First antennomere with four campaniform sensilla, second with small seta on side at base and group of six peg-like sensilla at apex: one prominent (sensory appendix) and five small.

Labrum wider than long, anterior margin shallowly emarginate ( Figs 16, 17 ). Dorsal side of labrum with a medial row of four setae and two pairs of campaniform sensilla placed centrally. Anterior margin with 16 setae: eight short, thin placed medially (not visible from dorsal side) in shallow emargination, three stout, long, placed on each lateral side, and one slim, long placed dorsally between thin and stout setae. A pair of fine setae, four campaniform sensilla, and 16 small sensilla usually arranged in four groups (each with four sensilla) in the mid part of ventral surface (epipharyngeal area). Numerous small spines in the central and lateral parts of ventral side of labrum.

Mandibles heavily sclerotized, palmate, with four distinct, triangular, apical teeth in one row, and two setae and two campaniform sensilla at base dorsally ( Figs 18, 19 ).

Maxillae and labium connate ( Figs 20, 21 , 42 ). Each stipes (st) with three pointed setae. Mala (mal) not distinctly bordered from palpifer (pp), broad, truncate at the apex, bearing: six pointed setae, single blunt seta, one peg like sensillum and one campaniform sensillum. Dorsally palpifer covered with spines ( Fig. 21 ). Ventrally palpifer with two setae and two campaniform sensilla ( Fig. 20 ). Maxillary palp 2-segmented: first segment (mpI) with 2 setae and one campaniform sensillum, second segment (mpII) with a group of sensilla at apex, and one campaniform sensillum and one seta below the apex. Labial palp (lp) one-segmented with a group of sensilla at the apex ( Fig. 42 ) and single campaniform sensillum below the apex. Hypopharynx (hyp) covered with numerous spines, with four campaniform sensilla at base. Prementum (pre) with two setae and four campaniform sensilla. Postmentum (post) with six setae.

Legs elongate ( Figs 23 , 30, 32 ), 3-segmented, consisting of: coxa, femur, tibiotarsus and pretarsus. Internal side of coxa with setae arranged in three groups: first group with two short, pointed setae (placed at border between coxa and body); second with three pointed setae; third with three short pointed setae and one long seta. Two short, pointed setae on coxa externally. Femur with eleven long setae (two of them very long, 2–3 times longer than remaining setae on femur, placed ventrally) and a short seta placed dorsally close to the base. Moreover, base of femur with a group of five campaniform sensilla and very short-pointed seta internally, one campaniform sensillum ventrally, and two campaniform sensilla externally. Two long apically blunt setae on tibiotarsus dorsally. Pretarsus heavily sclerotized, in form of short and curved, single, and simple claw armed basally with a pointed seta. Claw surrounded by a group of six blunt, apically curved setae; pointed seta and two campaniform sensilla dorsally at base of claw.

Fifth instar (mature) larva

( Figs 7, 8 , 44, 45 , 48–64 )

Measurements in mm (n = 8): length of body: 7.40–10.50; width of body: 3.50–4.50; length of supra-anal processes (measured like in Fig. 8 ): 2.00; width of head: 1.50–1.65 ( Table 1 ). Length of body was measured without head, from anterior border of pronotum to the base of supra-anal processes; width of body was measured across metanotum without lateral scoli.

Alive larva yellow whereas larvae preserved in alcohol straw-coloured (yellowish-white) with brown head, lateral scoli and spiracles; supra-anal processes brown ventrally and with four brown spots at base dorsally; coxae brown, femora brown at base and around distal part, tibiotarsi brown dorsally ( Figs 7, 8 , 44, 45 ). Body elongate-oval, slightly flattened dorso-ventrally, widest across meso- and metathorax, abdominal segments very slightly narrowed posteriorly ( Figs 44, 45 ). Sixteen pairs of lateral scoli and a pair of supra-anal processes: four pairs of lateral scoli on prothorax, two pairs on meso- and metathorax, and a pair on each abdominal segment (I–VIII). No scoli at the level of the thoracic spiracles. First three thoracic lateral scoli placed close each other, scoli of first pair pointed in direction of head; scoli of third pair shorter than remaining thoracic scoli, pointed opposite to scoli of first pair. Scoli of anterior meso- and metathoracic pairs slightly shorter than of posterior pairs. Abdominal scoli similar in size with thoracic scoli. In general, all lateral scoli short (in relation to the body width), approximately as long as 1/4 of width of segment on which they are placed. Scoli without lateral branches, covered with setae (each placed in tiny tubercle) and apically armed with pointed seta ( Fig. 51 ). Supra-anal processes short and stout, bent dorsally, covered with pointed setae in 2/3 basal length, without apical seta ( Figs 8 , 44 ).

Anal turret distinct and 2-segmented ( Fig. 45 ).

Nine pairs of spiracles (one pair on thorax and eight on abdomen). Diameter of spiracles slightly decreasing posteriorly. Thoracic spiracles with the largest diameter and last abdominal spiracle with the smallest diameter visible from lateral side. Abdominal spiracles I–VII well visible from dorsal view ( Fig. 44 ).

Body granulated (pronotum and sternites less granulated than the rest of tergites) with pointed setae on tergites and sternites ( Figs 48–50 , 52, 53 ). Setae of sternites mostly longer than those on tergites. Most setae of tergites placed on tiny tubercles. Setae on pronotum distributed regularly on whole surface, setae along lateral side shorter than setae placed in the middle, along body axis ( Figs 48, 49 ). Meso-, metanotum and abdominal tergites with two minute setae at anterior border medially and two rows of setae which running across segment ( Fig. 50 ). Setae equally numerous on each tergite. Two minute setae at anterior border of pro-, meso- and metasternum. Medially pro-, meso- and metasternum with two groups of setae placed anteriorly (very close to each other) and two groups of three setae placed posteriorly ( Fig. 52 ). Each abdominal sternite with two minute setae at anterior border and with irregular row of pointed setae running across segment. Setae placed medially on abdominal sternite I–V longer and more numerous than setae placed laterally and on remainder abdominal sternites ( Fig. 53 ).

Head well sclerotized, hypognathous, retracted into pronotum. Median suture complete, connected with frontoclypeal suture. Clypeus distinct, wider than long, with a pair of setae and a pair of campaniform sensilla ( Fig. 54 ). Six, distinct stemmata on each side of head.

Four, vertical, minute setae on each side of head (V 1–4); numerous, pointed setae on frontal side and 5– 6 pointed setae on each temporal side of head ( Figs 54, 55 ).

Antennae 2-segmented, set in membranous ring ( Fig. 62 ). First segment stout, wider than long, the second longer than wide. First segment with four campaniform sensilla, second with small seta on side at base and group of six peg-like sensilla on the apex: one prominent (sensory appendix) and five small.

Labrum wider than long, anterior margin distinctly emarginate ( Figs 56, 57 ). Dorsal side of labrum with a medial row of four long setae and two pairs of campaniform sensilla placed centrally. Anterior margin with 14 setae placed ventrally and two dorsally. A pair of small setae, four campaniform sensilla, and four groups of 4–5 small sensilla placed in the mid part of ventral surface (epipharyngeal area). Numerous small spines on over most of the ventral side of the labrum.

Mandibles heavily sclerotized, palmate, with four triangular, apical teeth, and two setae and two campaniform sensilla at base dorsally ( Figs 58, 59 ). Margins of mandibular teeth finely crenulate.

Maxillae and labium connate ( Fig. 60 ). Each stipes (st) with three pointed setae. Mala (mal) not distinctly bordered from palpifer (pp). Six long pointed setae, single blunt seta, one peg like sensillum and one campaniform sensillum at the apex of broad, truncate mala. Dorsally palpifer covered with spines ( Fig. 61 ). Ventrally palpifer with two long setae and two campaniform sensilla. Maxillary palp 2-segmented: first segment (mpI) with two setae and one campaniform sensillum, second segment (mpII) with a group of sensilla on apex, and with one campaniform sensillum and one pointed seta below the apex. Labial palp (lp) one-segmented with group of sensilla on the apex and campaniform sensillum below the apex. Hypopharynx (hyp) covered with numerous spines, with four campaniform sensilla at base. Prementum (pre) with two pointed setae and four campaniform sensilla. Postmentum (post) with about 12 pointed setae.

Legs stout, consisting of coxa, femur, tibiotarsus and pretarsus, all segments covered with pointed setae, more or less of the same length, distributed like on figures 63, 64. Additionally, four short pointed setae on coxa externally; group of five campaniform sensilla and short pointed seta at base of femur internally, one campaniform sensillum ventrally, and two campaniform sensilla externally. Pretarsus heavily sclerotized, short and curved, single and simple, armed basally with pointed seta. Pointed seta and two campaniform sensilla dorsally at base of pretarsus.

Pupa

( Figs 9, 10 , 46, 47 )

Measurements in mm (n = 6): length of body: 9.00–10.00; width of body: 3.10–4.80; length of pronotum: 2.10–2.80; width of pronotum: 5.20–5.60. Length of body was measured from anterior border of pronotum to the posterior border of abdominal segment VIII (at base of supra-anal processes); width of body was measured across third abdominal segment, without lateral scoli.

Body rounded-oval to elongated, surface distinctly texturized, living pupae yellow ( Figs 9, 10 ), preserved in alcohol—straw-coloured; in both alive and alcohol-preserved pupae, tips of lateral processes of abdominal segments I–V and spiracles of abdominal tergites I–V black ( Figs 46, 47 ). Body covered with numerous, regularly distributed minute setae, each placed on tiny tubercle (tubercles smaller than those on the lateral scoli of the mature larva). Numerous spinules in posterior part (along posterior margin) of abdominal tergites; number of spinules on successive segments gradually increases posteriorly.

Vertex of head with two conic projections (in ventral view) ( Fig. 47 ). Anterior margin of pronotum rounded, with central area straighter, with a small notch medially (not so clearly visible in all specimens); presence of two pairs of very short (hardly visible), conical, marginal processes with tiny tubercles bearing single seta. Posterior angles of pronotum projected backwards, slightly curved inward, covered with minute setae, each placed on tiny tubercle.

Pro-, meso- and metanotum without lateral scoli. Abdominal segments I–V with a pair of conical, pointed forward lateral scoli which gradually shortened posterad; scoli covered with tiny tubercles bearing single seta; a group 3–6 setae at the apex of each scolus. Lateral scoli of segments VI–VIII short, thin, in form of simple processes, pointing backwards. Lateral scoli of abdominal segment VI ended with single seta; scoli of segments VII and VIII without setae. Segment IX with a pair of short processes (shorter but stouter than scoli of abdominal segments VI–VIII) covered with numerous spinules which look like spinules on tergites. Diameter of spiracle of each abdominal pair decrease posteriorly. Spiracles of abdominal tergites I–V slightly elevated from body level, spiracles of abdominal segments VI–VIII visible only on microscopic slides. The cast skin of the last instar is retained by the pupa ( Figs 46, 47 ).

Biological notes

Adults, larvae and egg masses were found on the host plant ( Figs 1–6 ). The eggs are laid in groups (egg mass), in horizontal, overlapping layers with among 12 to 35 eggs, covered by a dark, rounded faecal shield ( Figs 2–4 ). The egg mass is always laid in the fork of twigs where the branches leave the main trunk ( Fig. 2 ). Once hatched, the larvae group at the leaf margin where they are feeding (mainly first and second instar) and in older instars the groups become less numerous; groups of larvae forming circles were also observed ( Fig. 5 ), where larval heads were turned to the centre of the group (cycloalexy). After each molt the exuvia remains attached to the supra-anal process together with moist faeces, forming a triangular mass that can be moved up and down by the larva when disturbed. Also, when disturbed, larvae tend to disperse ( Fig. 6 ).

Most of the egg masses sampled (n=13) were parasitized by a Chalcidoidea microhymenoptera or developed fungi and no larva hatched from them. The egg parasitoid should belong to Emersonella Girault, 1916 ( Eulophidae ), known to parasitise Hybosa and recorded as egg parasitoid of Neotropical Cassidinae ( Cuignet et al. 2007) . From the two remaining egg masses 38 larvae hatched (in one group 14 and in the other 24 larvae) which had a high mortality under laboratory conditions (28 oC; ca. 75% RH). The developmental time under laboratory conditions from first instar larva to adult was estimated at 21 days.

Figures

FIGURE 11. Hybosa acutangula, first instar larva, dorsal aspect; arrow 1 points to additional tubercle placed between scoli of second and third pair; arrow 2 points to the place where the scolus of the fourth pair should be.

FIGURE 12. Hybosa acutangula, first instar larva, chaetotaxy of tergites, part of granulation was removed on right side of body to expose setae.

FIGURE 13. Hybosa acutangula, first instar larva, chaetotaxy of sternites.

FIGURES 14–22. Hybosa acutangula, first instar larva. 14. Frontal side of head; 15. temporal side of head; 16. ventral side of labrum; 17. dorsal side of labrum; 18. mandible, dorsal aspect; 19. mandible, ventral aspect; 20. maxillae and labium; 21. palpifer and maxillary palp; 22. two aspects of antenna.Abbreviations: hyp—hypopharynx; lp—labial palp; mal—mala; mpI—first segment of maxillary palp; mpII—second segment of maxillary palp; post—postmentum; pp—palpifer; pre—prementum; st—stipes.

FIGURES 23. Hybosa acutangula, leg of first instar larva.

FIGURES 24–29. Hybosa acutangula, first instar larva. 24, 25. Setae at base of lateral scoli, place ventrally; 26. additional tubercle placed between lateral scoli of second and third pair; 27. top of sensillum of additional tubercle; 28. lateral scolus of last abdominal segment; 29. top of sensillum of last abdominal scolus.

FIGURES 30–36. Hybosa acutangula, first instar larva. 30. Top of leg, arrow points to position where one seta is missing on the side of claw, pointed seta at base of the claw is also invisible in this aspect; 31. spiracle of thorax; 32. leg, one of the six setae surrounding the claw is missing, pointed seta at base of claw is visible—arrow points to this seta; 33. spiracles of abdominal segment I and II; 34. asperities on supra-anal process; 35. supra-anal processes; 36. top of supra-anal process.

FIGURES 37–43. Hybosa acutangula, first instar larva. 37. Head; 38. stemmata; 39, 40. setae of frons of head; 41. minute seta on vertex of head; 42. labial palp; 43. antenna.

FIGURE 1–6. Hybosa acutangula. 1. Alive adult; 2. ootheca laid on the host plant, dorsal aspect; 3. ootheca removed from host plant, dorsal aspect; 4. Ootheca removed from host plant, ventral aspect; 5, 6. larvae in natural environment, on the host plant.

FIGURE 7–10. Hybosa acutangula. 7. alive mature larva; 8. supra-anal processes of mature larva, Ls-ap—length of supra-anal processes; 9, 10. alive pupa with attached last larval skin.

FIGURES 44–47. Hybosa acutangula. 44. Mature larva, dorsal aspect, the white arrow points out an additional scolus, present in the larvae of the first instar in the form of a tubercle, the black arrow points out the location of the thoracic spiracle and the lack of scolus; 45. mature larva, ventral aspect; 46. pupa, dorsal aspect, scoli of first abdominal segment partially covered with elytra; 47. pupa, ventral aspect.

FIGURES 48–51. Hybosa acutangula, mature larva. 48. Setae of pronotum medially; 49. setae of pronotum laterally; 50. setae of first abdominal tergite (first row of setae); 51. lateral scolus of first abdominal segment (dorsal aspect).

FIGURES 52, 53. Hybosa acutangula, mature larva. 52. Metasternum; 53. second abdominal sternite.

FIGURES 54–62. Hybosa acutangula, fifth instar larva. 54. Frontal side of head; 55. temporal side of head; 56. dorsal side of labrum; 57. ventral side of labrum; 58. mandible, dorsal aspect; 59. mandible, ventral aspect; 60. maxillae and labium; 61. palpifer and maxillary palp; 62. two aspects of antenna. Abbreviations: hyp—hypopharynx; lp—labial palp; mal—mala; mpI—first segment of maxillary palp; mpII—second segment of maxillary palp; post—postmentum; pp— palpifer; pre—prementum; st—stipes.

FIGURES 63, 64. Hybosa acutangula, leg of fifth instar larva. 63. internal aspect; 64. external aspect.

Tables

TABLE 1. Measurements of egg, egg mass, first and fifth instar larva and pupa of Hybosa acutangula (Coleoptera, Chrysomelidae, Cassidinae).

egg	length [mm]	width [mm]
1.	1.40	0.90
2.	1.40	0.80
3.	1.30	0.90
4.	1.50	0.95
5.	1.30	0.90
egg mass	length [mm]	width [mm]
1.	6.00	4.50
2.	4.80	4.50
3.	6.00	5.30
first instar larva	length of body [mm]	width of body across metathorax [mm]	length of supra-anal processes [mm]	width of head [mm]
1.	0.85	0.55	0.75	0.40
2.	0.95	0.56	0.80	0.40
3.	1.10	0.55	0.80	0.40
4.	1.25	0.57	0.78	0.42
5.	1.25	0.55	0.80	0.42
6.	1.30	0.60	0.87	0.42
7.	1.25	0.57	0.82
fifth instar larva	length of body [mm]	width of body across metathorax [mm]	length of supra-anal processes [mm]	width of head [mm]
1.	10.50	4.40	2,00	1.52
2.	7.50	4.00	2,00	1.55
3.	7.40	3.50	2,00	1.65
4.	10.00	4.10	2,00	1.50
5.	8.00	4.00	2,00	1.60
6.	8.50	3.80	2,00	1.65
7.	9.00	4.50	2,00	1.50
8.	9.00	4.10	2,00	1.60
pupa	length of body [mm]	width of body across 3rd abdominal segment [mm]	length of pronotum [mm]	width of pronotum [mm]
1.	9.00	3.70	2.10	5.20
2.	10.00	3.60	2.60	5.60
3.	9.00	3.70	2.50	5.40
4.	9.90	4.80	2.80	5.50
5.	9.90	4.60	2.60	5.50
6.	9.00	3.10	2.30	5.10