Acentroptera basilica Thomson 1856
Creators: name: Albertoni, Fabiano F.
name: Casari, Sônia A.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Acentroptera
Acentroptera basilica

description: Acentroptera basilica Thomson, 1856
(Figs 1–52)
Description of mature larvae (Figs 1–19, 47–50). Length: 10–11 mm (n=4).
Body elongate, wide, strongly dorso-ventrally flattened. Coloration cream after fixation; when alive (Figs 48– 50) cream and yellow spotted laterally, slightly sclerotized; head strongly sclerotized, yellowish-brown with frons darker; mandibles, endocarina and hypostomal rods dark-brown; prothorax yellowish; legs yellowish-brown, partially brown. Pubescence not visible under stereoscopic microscope, except on the head, with tiny setae, represented in illustrations (Figs 3, 4) only by punctures. Metathorax and abdominal segments I–VII (Figs 1, 2, 48– 50), each with one dorsal and one ventral, transverse, elliptical, granulated band in middle; ventral granulation weakest.
Head (Figs 3, 4, 7–11, 48, 50) prognathous, narrower than prothorax, partially retracted into prothorax; epicranial stem absent; median endocarina well-developed, extending between frontal arms, not reaching anterior margin; frontal arms V-shaped. Six black stemmata on each side: 4 lateral or dorsolateral and 2 ventral. Frons with 6 pairs of tiny setae: one pair on each side near anterior margin, a row with 3 setae on each side of endocarina and one pair on sagittal line; each epicranial half with 9 setae: 3 longest near stemmata and 6 in an irregular row near each frontal arm. Hypostomal rods well-developed. Frontoclypeal suture weakly marked. Clypeus (Fig. 12) transverse with 5 pairs of tiny setae. Antenna (Figs 10, 16) with 3 antennomeres; basal antennomere as long as wide, with 3 dorsal tiny setae; median antennomere, longer than wide, bearing 2 dorsal tiny setae near anterior margin, and one membranous, cupuliform, sensorial appendix at apex; sensorial appendix as long as distal antennomere; distal antennomere reduced, narrower than ¼ of median antennomere width near apex, inserted latero-internally at apex, side by side with sensorial appendix, bearing at apex one long and stout seta, and 3 short setae. Labrum (Figs 10, 12) band-like, strongly emarginated in middle; with one pair of tiny setae on each side and a dense fringe of setae at anterior margin. Epipharynx (Figs 11, 13) densely setose; setae very long near anterior margin and in middle; microspined below long setae area. Mandible (Figs 11, 18, 19) robust; lateral margin sinuous on basal half; 3 dorsal and 3 ventral subapical, rounded teeth; with one lateroventral tiny seta near base. Maxilla (Figs 8, 11, 14): cardo reduced triangular; palpus indistinguishable; stipes with lateral margin rounded, narrowed at base; with 3 tiny setae laterally; mala triangular, densely setose, brush-like near apex and with one lateral tiny seta near base. Labium (Figs. 8, 11, 14) elongate; palpi indistinguishable; prementum with sclerotized transverse band bearing 2 pairs of tiny setae at base; ligula densely setose, brush-like on distal half; setae surpassing anterior margin; postmentum elongate with 3 pairs of tiny setae. Hypopharynx (Fig. 15) densely setose, brush-like at distal region; basal region with one transverse sclerite in middle and one elongate and U-shaped sclerite on each side; three campaniform sensilla on each side, near base.
Thorax. Prothorax wider than long, longer than meso- and metathorax combined; anterior margin with narrow granulated band. Meso- and metathorax band-like; mesothorax dorsally and ventrally, grooved transversely near middle; metathorax with dorsal, transverse, elliptical, granulated band, transversely grooved in middle, and ventrally with 2 smaller areas weakly granulated. Metathorax with one rounded spiracle on each side, located in a short lateroanterior tubular projection. Legs (Figs 2, 17, 49) widely separate, located ventrolaterally; robust and 4- segmented; coxa short, band-like; trochanter and femur fused, wider than long, with setae forming irregular transverse median row; microsetae (represented by punctures) more concentrate near ventral margin; tibia almost triangular with setae near anterior margin; tarsungulus slightly sclerotized with one lateroexternal seta at base.
Abdominal segments I–VIII with a rounded lateroventral short lobe; segments I–VII band-like, each with transverse, elliptical, granulated band, dorsally and ventrally; each elliptical, granulated band with a transverse groove in middle; ventral areas weakly granulated; each side of abdominal segments with one dorsolateral spiracle, smaller than thoracic, located in a short tubular projection. Segment VIII slightly narrower than segment VII, with transverse groove dorsally. Segment IX narrowest, as wide as half width of segment VIII, with two apical projections, each with one spiracular opening at apex. Segment X ventral, reduced and rounded, anal opening transverse.
Description of pupa (Figs 20–25, 51, 52). Length: 9–11 mm (n=2).
Coloration cream after fixation; when alive (Figs 51, 52) cream and yellow spotted laterally; segment IX slightly sclerotized; dorso-ventrally flattened with sclerotized areas and brown microspines; each microspine with one short, whitish seta at base (not represented on illustrations); setae longer than microspines.
Head partially visible from dorsal view, with fore angles prominent and rounded.
Pronotum wider than long, narrowed anterad; lateral margin with rounded prominence near middle. Metanotum longer than mesonotum.
Abdomen elliptical, wider on segments III–V. Each abdominal segment with lateroventral projection bearing microspines or small tubercles near apex; projections of segments I–VI with apex slightly dilated and rounded; projections of segment VII with apex strongly dilated; and those of segment VIII with apex bifid. Segments I–VII band-like; segments III–IV each with one pair of dorsolateral tubular projection with rounded spiracular opening at apex; segment V with one pair of dorsolateral spiracular opening, slightly sclerotized, horn-like, elongate, widest and rounded at base. Segments II–VIII grooved transversally with two transversal bands of microspines dorsally; segments VI–VIII with some dispersed microspines ventrally. Segment IX shorter and narrower than previous; each side with one projection bearing large microspines, as large as those on lateral projections of segment VIII, and two small projections in middle, each with 3 spines. Segment X reduced, placed ventrally; anal opening transverse in male and Y-shaped in female.
Description of male and female genitalia (Figs 30–44)
Male (Figs 30–37). Aedeagus (Figs 30–35) elongate, dorso-ventrally curved, basally slightly flattened; basal portion weakly sclerotized. Median lobe wide, slightly narrowed and most sclerotized at apex; in a 90° angle with manubrium. Apical flap (Figs 31, 34, 35) rounded at apex, and convex dorsally, flanking ostium. Tegmen Yshaped; manubrium relatively short and wide, almost as long as arms; with a longitudinal depression in middle; apex truncate; wider on ventral than lateral view; arms curved. Pygidium (tergite VII) (Fig. 37) wider than long, with distal margin prominent in middle, coarsely punctate, apex rounded bearing small and thin setae. One internal sac sclerite (endophalic sclerite) (Figs. 31–33), well sclerotized and bearing one long and sharp hook apically; bilobed and membranous at base. Spiculum gastrale (Fig. 36) V-shaped with a small projection mesally.
Female (Figs 38–44). Sternite VIII (Figs 39, 44) lozenge–like, barely sclerotized, with thin membranous area near apex of posteromedian lobe; two lateral, narrow arms on each side; posteromedian lobe weakly developed, widely rounded, bearing few setae; spiculum gastrale single, elongate, more sclerotized than sternite VIII, with slightly expanded and membranous apical margin. Spermatheca (Fig. 43) cylindrical, elongate, sinuous, narrowed apicad, sclerotized, with one relatively rounded receptacle; receptacle narrowed at extremity (duct region) and one duct insertion at the extremity of receptacle; spermathecal duct long and coiled; pump area strongly deflected, around five times longer than receptacle; apical appendix short. Proctiger (tergite IX) (Figs 42, 44) mostly membranous, partially slightly sclerotized (darkened area of Fig.42), both pieces connate by thin membrane. Valvifer absent or fused to coxite; apex of coxite with several setae; median plates absent. The paraproct and the stylus were not observed.
Material examined. Brazil. Bahia: Feira de Santana, Universidade Estadual de Feira de Santana (UEFS), host plant Aechmea aquilega (Bromeliaceae), 12°12´S, 38°58´´W, 23.V.2010, M.A. Ulyssea leg., 4 larvae; 2 larval exuviae; 7 exuviae of head (1 dissected); 2 pupae (1 ♂, 1 ♀); and 12 adults (4 ♂, 5 ♀, 3 undetermined, but probably females) (MZSP).
Geographical distribution. Argentina, Brazil (Bahia, Rio de Janeiro, São Paulo), French Guiana, Paraguay (Staines 2014; present work). Bahia is here recorded by first time.
Biology of Acentroptera basilica Thomson, 1956 (Figs 45–52)
Adults of A. basilica (Figs 26–29) were observed in field from the end of April (moderate temperatures - around 25.5°C, and the beginning of a low mean rain falls—around 30 mm /last 10 days of the month) to around middle of June, 2010 (moderate temperatures—around 25°C and beginning of highest mean rain fall of the year). After this period, the adults reappeared in middle of September, 2010 (relatively low temperature—22.5°, and beginning of drought period). By the end of October (moderate temperatures—around 25°C, and low precipitation—around 40 mm /month) the adult population increased amazingly: in 3 bromeliads were counted a total of 23 individuals; in other 2 plants a total of 20, and in one other plant ten. At the beginning of November (moderate temperature—around 25°C, and drought period—around 4.6 mm/month) they disappeared, and reappeared again in middle of January, 2011 (moderate temperature—around 25°C, and low rain fall). During these periods, they were found frequently in activity (feeding and/or copulating) in the morning and afternoon.
Otherwise, they used to be hiding around 10:30h to 15:30h, during the hottest periods of the days. These behaviours let us to conclude that the adults were more abundant during the period of moderate temperatures and low precipitation. During the periods of highest precipitation of the year, in June (middle on), July and August were not observed active adults. Considering that the oviposition occurs most likely near the leaf axil, lower precipitations values would be important to avoid eggs drowning.
During the activity periods, the adults were scraping leaves of Aechmea aquilega Salisb., more frequently on the adaxial face of the leaf (Figs 45, 46), corroborating that they are external feeders. This same feeding habit was observed in adults of A. pulchella (Mantovani et al. 2005; Magalhães et al. 2012). In captivity they lived for relatively short time; the greatest longevity was a female that lived for approximate two months. It was also observed, after dissection of 6 specimens (4 females, 2 males) preserved in ethanol, that the females are larger than males. This sexual dimorphism was corroborated during copulation in the field and lab conditions. Usually, males have darker patches than females (Figs 26, 27). Otherwise, it was not observed or noticed another sexual dimorphism feature.
Eggs of A. basilica were not found. Five months after collecting the adults, the blotch mine with mature larvae was observed (Fig. 47). Seven larvae were found inside the same and strongly damaged leaf, mining widely throughout the whole leaf. Frass was left into the mine, showing the paths of the larvae in the dried leaf. Other leaf strongly damaged, was also found, with seven head exuviae inside the mine. This let us to conclude that, the development of the larvae, from first to penultimate instars, occurred inside of a single leaf and after, they migrated for another fresh leaf to continue feeding. Some days after the first observation the larvae were dispersed in three different leaves. One migrated by itself and two others were transferred to two different leaves by us. However, within three days all larvae were grouped inside the same leaf, suggesting some level of gregarious behaviour.
description: Published as part of Albertoni, Fabiano F. & Casari, Sônia A., 2017, The natural history and morphology of two bromeliad associated hispines from Brazil: Acentroptera basilica Thomson, 1856 and A. cf. tessellata Baly, 1958 (Coleoptera: Chrysomelidae: Cassidinae: Sceloenoplini), pp. 521-543 in Zootaxa 4243 (3) on pages 523-530, DOI: 10.11646/zootaxa.4243.3.6, http://zenodo.org/record/400175