Americerura brasiliensis St Laurent, Carvalho and Orlandin 2024, sp. n.
Creators: name: St Laurent, Ryan A.
name: Carvalho, Ana Paula S.
name: Orlandin, Elton
name: Carneiro, Eduardo
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Lepidoptera
Notodontidae
Americerura
Americerura brasiliensis

description: Americerura brasiliensis St Laurent, Carvalho and Orlandin sp. n.
(Figures 14–16, 17 a, 18 a–f,j–m, 19g,h,j); Accession numbers: DZUPIL 169
Diagnosis
Larva. First-instar larvae can be easily recognised among the species discussed in the present text by the presence of extremely long spined stemapods and a silvery grey lateral band. The laterally striped pattern of intermediate instars is also unique to this species. Ultimate instars of A. brasiliensis are recognisable by their highly spotted pattern with a combination of green flecks and purplish-brown spots. Americerura argynnis larvae are similar since they are also speckled and have brown dorsal saddles, but the speckles of A. argynnis are not both green and brown as in A. brasiliensis. The paraprocts of A. brasiliensis are longer than in any previously discussed species. The related Americerura rarata has a similar (compare Figures 17a and 17b) larva but lacks the purplebrown specks and has yellow extendable parts of the stemapods; these are red and yellow in A. brasiliensis. Furthermore, the thoracic protuberance at T3 is much more accentuated and extended in A. brasiliensis and the lighter portions of the dorsal saddle are yellower in A. brasiliensis whereas the same regions are white in A. rarata.
Adult. Unlike all other Americerura in south-east Brazil and adjacent countries, A. brasiliensis lacks any yellow-filled spots on the forewings. The male terminalia are also highly distinct due to the presence of bifurcating spines on the VIII sternite. Americerura brasiliensis is very similar to the widespread A. rarata which was described from Texas and is otherwise well known from Mexico and throughout Central America. Americerura brasiliensis belongs in a species complex with A. rarata and other undescribed species in Central and South America that have the same forewing patterning lacking yellow spotting. However, A. brasiliensis is a slightly larger species than typical A. rarata and has somewhat less lustrous scales, it is more darkly maculated (especially in females, with a darker abdomen), and the medial lines are thicker and usually coalesce along the anal angle of the forewing. Genitalia are very similar in the two species.
Etymology
The new species is named for Brazil, the type locality and country from which all confidently identified specimens of this taxon originate.
Type material
Holotype. BRAZIL: Rio Grande do Sul. 1 male with the following label data (different labels separated by forward slashes), for non-abbreviated type locality see paratype information below: ̎BRASIL, RS, Eldorado do Sul, Pq. Eldorado. Est. Exper. Agro., 30° 05 ʹ 31̎S 51°40 ʹ 15̎ W, 22.XI.2022, St Laurent & Carvalho leg., Ex larvae/GEN. PREP. E. Orlandin 2023, DZ57.361/HOLOTYPUS (DZUP).̎
Paratypes
BRAZIL: Paraná: 1 male, S [ão] Luiz do Purunã, 1100 m, XII.1969, V. O. Becker leg., Col. BECKER No. 1234, St Laurent diss.: 11–28-22:1 (USNM). 1 female, Castro, Collection Wm Schaus, St Laurent diss.: 11–28-22:2 (USNM). Santa Catarina: 1 male, Blumenau ̍675 X ̾, Pohl, St Laurent diss.: 11–28-22:4 (USNM). 1 male, Neu Bremen, 13.XI.1934, Fritz Hoffmann (CUIC). 1 male, Neu Bremen (CMNH). 17 males, Neu / Nova Bremen, 13.XI.1934 (1 male), 1. X.1936 (2 males), 3.X.1936 (1 male), 13.X.1936 (1 male), 15.X.1936 (1 male), 16.X.1936 (1 male), 18.X.1936 (1 male), 5.XI.1936, 1.XII.1936 (1 male), 8.XII.1936 (1 male), 9.XII.1936 (1 male), 14.XII.1936 (1 male), 17.XII.1936 (1 male), 19.XII.1936 (1 male), 11. I.1937 (2 males), Fritz Hoffmann (CUIC). Rio Grande do Sul: 9 males, 1 female, Pelotas, 20.IX.1938 (1 male), 14. I.1951 (1 male), 14.XI.1951 (1 male), 30. I.1952 (1 male), 19.XII.1952 (1 male), 23. I.1953 (5 males), C. M. de Biezanko (CUIC). 1 male, Guarani, 11.IV.1932, C. M. de Biezanko (CUIC). 1 female, Eldorado do Sul, Parque Eldorado, Estação Experimental Agronômica, −30.091985°, −51.671020°, 17.IX.22, leg. St Laurent and Carvalho [source of the eggs used for our rearing and all subsequent paratypes] (DZUP). 6 males, 7 females, Eldorado do Sul, Parque Eldorado, Estação Experimental Agronômica, −30.091985°, −51.671020°, reared from eggs on Xylosma pseudosalzmannii during IX–XI.2022, derived from wild-caught paratype female, St Laurent and Carvalho leg. (DZUP). Immature stages: 001.1– 5 eggs, 6 first-instar larvae; 001.2–4 second-instar larvae; 001.3–3 third-instar larvae; 001.4–3 fourth-instar larvae; 001.5–2 fifth-instar larvae; 001.6–7 first-instar head capsule; 001.7– 11 second-instar head capsules; 001.8–9 third-instar head capsules; 001.9–6 fourth-instar head capsules; 001.10–2 fourth-instar head capsule; 001.11–3 fifth-instar head capsules. PARATYPUS, Americerura brasiliensis, IX-X-2022, Parque Eldorado, Eldorado do Sul, Rio Grande do Sul, St. Laurent leg./ PARATIPO /DZUPIL 0169.
Adult description
Description
Male. (Figure 19g, h) Head: Width more than half that of thorax, frons white, eyes large, naked, occupying more than 2/3 area of head, eyes bordered posteriorly by dark brown scales; labial palpus highly reduced, not extending beyond frons, two segmented, clothed in dark brown scales; haustellum vestigial but present, antennal scape scaled in erect tuft of white scales, antennae light brown with white scales coating dorsal surface, bipectinate to tip with rami increasing in length from antennal base to slightly more than half antennal length where rami lengths abruptly become shorter, remaining short until terminus. Thorax: Ground colour scales white, prothorax with black posterior margin of scales, additional individual black spots situated more posteriorly which may or may not merge to form a black band, further thoracic spots present mesally and posteriorly on thorax dorsal surface, thorax overall thickly scaled. Legs mostly concolorous with thorax, clothed in long, fine, white scales, leg segment intersections with black scales, tarsi black scaled. Tibial spurs thin, short, clothed in fine white scales, in formula 0-2-2. Tarsal claws simple. Forewing length 13–17 mm, average 14.4 mm (n = 8); subtriangular, outer margin convex. Forewing dorsum ground colour shiny white, ground colour uniform across entire wing except for contrasting black lines. Overall wing pattern rather complex, best described by presence of five lines: a zigzagging antemedial line with a smaller black patch of scales present inwardly at base of wing near thorax, a wavy medial line, a second more zigzagging medial line, and a pair of zigzagging postmedial lines that jut sharpy outward at intersections with veins. Subapically, postmedial line thicker and appearing as a splotch, other lines thickest costally and along anal margin of wing. Along anal margin two medial lines and innermost postmedial line coalesce. Between antemedial line and medial line are variable black circles, one at anal angle and two near costa that variably connect. Discal spot absent. Wing margin with black marks between veins. Forewing ventrum mostly unmarked except for subapical and costal marks, faint postmedial line may be present, and intervenular black marks at wing margin. Hindwing dorsum mostly pure white but a few black scales may be present at margin and anal angle. Hindwing ventrum as for hindwing dorsum, usually without black scales. Frenulum a single bristle. Wing venation as for other Americerura, with a small accessory cell and radial veins arising from its apex. Abdomen: Dorsally covered in black except terminal two segments that are mostly white, separation between abdominal segments poorly defined, ventrally white. Eighth sternite (Figure 18c,f) with complex seven-pronged, antler-like structure, consisting of two pairs of thin, sharp prongs that bifurcate and a shorter, broader, blunter mesal prong and two lateral prongs, distal half of longest pair of prongs more heavily sclerotised than remainder of tergite. Genitalia (Figure 18a,b,d,e) (n = 3) simple in overall structure, with ovoid vinculum, weakly connected ventrum. Tegumen poorly defined. Uncus simple, fingerlike and curved, blunt, heavily sclerotised and somewhat rugose, covered in setae. Socii simple, finger-like, upcurved and heavily sclerotised, dorsal edge irregularly toothed. Broad anal tube with mesal projection quite apparent below socii. Gnathos absent. Valvae simple, narrow, smoothly curved upwards. Juxta a thin sclerotised strip, partially fused to phallus. Phallus weakly sclerotised basally, becoming gradually more heavily sclerotised distally, apex downturned and sharp, vesica thin, simple, bag-like without cornutus.
Female. (Figure 19j) Sexual dimorphism not pronounced but female notably larger. Head: As for male but frons with brown scales ventrally, antennae with shorter rami. Thorax: As for male but in some specimens most of prothorax entirely covered in black scales. Forewing length 15–21 mm, average 17.1 mm (n = 9). Forewing dorsum as for male but wing broader, antemedial black circles larger and more evident. Forewing ventrum mostly unmarked but may have more dark brown to black scales distally than in male. Hindwing dorsum as in male, principally white. Hindwing ventrum as for hindwing dorsum, usually without markings. Frenulum with numerous tightly packed bristles. Abdomen: As for male but bulkier, segments more defined due to presence of white scales at segment margins. Eighth sternite simple, lacking five-pronged structure present in males. Genitalia (Figure 18j–m) (n = 2) simple; tergite VIII a thickly sclerotised band. Apophyses anteriores thick but relatively short; apophyses posteriores thin, not extending to margin of VIII. Lamella antevaginal plate membranous. Postvaginal plate very broad, being the single largest structure of the genitalia complex, plate with a heart-shaped ostium at its lobed base, lateral margins of postvaginal plate somewhat invaginated and ribbon-like, lateral components terminating in broadened, rectangular sclerotised pockets below and on either side of ostium. Ductus bursae indistinct; corpus bursae thin, bag-like, lacking signa, smaller than remaining genitalia complex. Papillae anales thin, outwardly spread, covered in long, fine setae.
Description of immature stages.
Egg. (Figure 14a,b) Average duration: ~10 days (n = ~64); 1.5 mm diameter (n = 5); circular, dorsally domed, base truncated and flattened. Colouration irrorated dark and light apple green, outer margin uniform pale green, continuous with basal truncated part; inner margin of dorsal aspect covered in reticulated light green patterning except in centre where dark green is more evident due to absence of reticulation, this region becoming darker as eclosion nears.
First instar. (Figure 14c) Average duration: ~7 days (n = 3); body length 5.5–6.9 mm without stemapods, 8.2–9.2 mm with stemapods (n = 7); head capsule width 0.58– 0.61 mm (n = 7), head hypognathous, glossy black. Body cylindrical, segments generally equal sized although thoracic segments slightly taller, T 1 with pair of relatively large scoli at lateral apices of segment angled overhead, scoli black with about 10 spines, each spine with single seta at apex, each seta longer than spine producing it; A 10 with black dorsal shield and pair of glossy black paraprocts; upon hatching general colouration black but with feeding subspiracular and ventral region noticeably more maroon in colour, supraspiracularly remaining black; pair of darker black supraspiracular lines present above a contrasting silvery grey lateral band that fades at anterior and posterior termini. Body naked except primary setae; thoracic legs black, A 3– A 6 prolegs coloured as for ventral portion of abdominal segments with black ring distally; crochets uniserial uniordinal; anal prolegs modified to form elongated black, extremely long-spined stemapods with maroon eversible component that is extruded when threatened, stemapod spines longest at terminus and along dorsal basal half.
Chaetotaxy. As in A. argynnis.
Second instar. (Figure 14d) Average duration: ~5–6 days (n = 2); body length 8.3–9.5 mm without stemapods, 12.8–14.3 mm with stemapods (n = 5); head capsule width 1.07– 1.11 mm (n = 11), gross morphology somewhat similar to first instar, but thoracic segments more noticeably defined and more rectangular in overall shape, forming a blunt point at T 3. Ground colouration reddish brown-green early in instar becoming light apple green as larva grows, dorsum dark brown appearing as narrow stripe except at T 1 where narrow pattern spreads to reach protuberances and along A 3– A 5 where saddle pattern spreads faintly laterally, one wider silver-grey lateral supraspiracular band, pair of fainter, thinner lateral supra- and subspiracular lines present, these two lines being somewhat intermittent. T 1 apical scoli more robust and stemapod spines smaller relative to body size although still with three to four spines dramatically larger than remainder of spines along stemapods, stemapods mostly black except for faint brown banding medially and terminally.
Third instar. (Figure 14e) Duration: 7 days (n = 1); body length 12.2–13.5 mm without stemapods, 16.1–20.4 mm with stemapods (n = 7); head capsule width 1.7–1.8 mm (n = 9) head colouration light brown with irregular darker brown patterning, gross morphology rather distinct from previous two instars but T 1 apical scoli more robust, thoracic segments much more noticeably defined and more rectangular in overall shape, abruptly projected hump formed at dorsum of T 3. Ground colouration as for second instar, but patterning distinct, less latitudinally striped and more finely delimited into the contrasting dark brown dorsal saddle-like pattern which is widest at A 4 and the light apple green lateral area, laterally scattered with lighter green speckles; spiracles more noticeable, orange; prolegs light green as for lateral area, stemapod colouration lighter brown with accentuated banding medially and near terminus, larger stemapod spines lighter brown in colour with dark brown apices, stemapods much more robust and more thickly spined than in previous instar, appearing saw-like.
Fourth instar. (Figure 14f) Duration: ~7 days (n = 1, other larvae took about 7 days but only one was formally tracked); body length 13.6–19.4 mm without stemapods, 20.8– 28.4 mm with stemapods (n = 4); head capsule width 2.57–2.70 mm (n = 6) gross morphology similar to third instar but T 1 apical scoli smaller relative to body, paraprocts thicker relative to body, hump at T 3 slightly more accentuated with a light grey colouration apically. Colouration nearly identical to third instar but dorsal saddle slightly more finely delimited and deeper chestnut brown, occasionally light brown in some individuals, both colour forms with longitudinal striations within saddle giving it a mottled, almost wooden, appearance; spiracles more noticeable, bright orange in colour, body overall more heavily speckled, stemapods lighter brown, especially laterally. Extendable portion of stemapods deep maroon with whitish tips.
Fourth-instar larvae moult into either a terminal fifth instar or a fifth instar followed by an ultimate sixth instar. They are described separately below.
Fifth instar (when ultimate). (Figures 15b, 16a,c) Duration: ~8 days (n = 1); body length 25–29 mm without stemapods, 35–49 mm with stemapods (n = 7); head capsule width 4.07 mm (n = 1), head colouration mostly brown with black splotches near apex. Morphology differs somewhat in the final instar. As in previous instars, thoracic segments enlarged and broad, forming a triangular shape when viewed from dorsum, but T 1 lacks spined scoli and instead bears shiny black protuberances giving the anterior of T 1 a squared appearance into which the head can be retracted, head held somewhat prognathous at rest. When threatened bright pink integument of T 1 immediately behind and above head exposed. T 3 with a greatly pronounced hump. Paraprocts robust, elongated, and black. Lateral area of body with bright apple-green ground colour with irregular light green specks as well as slightly larger purplish-brown splotches at base of most primary setae giving an overall densely spotted appearance; spiracles bright orange except that of T 1 which is darker brown and noticeably larger. Dorsum from head to A 10 with well-defined saddle-like pattern. Thoracic saddle shiny dark brown with lighter central stripe, saddle widest at T 1 becoming gradually narrower approaching the apical protuberance of T 3, from T 3 abdominal saddle widens in discrete increments at each segment, being widest at A 4 after which saddle gradually decreases in width along length of segment A 5, saddle of A 6 and A 7 narrow and uniform in width, widening again at A 8– A 10 merging with the anal plate; colouration of saddle on abdominal segments light brown with darker brown and light yellow striations, A 4 with a notably wider pair of dorsal yellow patches mesally, on A 4 above spiracle saddle projected ventrally along segment but not passing spiracle, above spiracle saddle may have zero, one, or two bright white patches; outer margins of thoracic and abdominal saddle outlined by bright white of variable thickness and distinctness. True legs black and green with black situated at base of each segment, prolegs apple green basally and reddish brown distally. Stemapods as in previous instars but thicker and more sharply spined along length, their colouration brown dorsally, but may be yellowish-green laterally, extendable part of stemapods bright yellow at base and tip with a broad red area in between.
Fifth instar (when proceeding to six instars). (Figure 15a) Duration: not recorded; body length 20.3–22.4 mm without stemapods, 27.7–33.2 mm with stemapods (n = 3); head capsule width 3.3–3.7 mm (n = 3) gross morphology as in fourth instar except head and paraprocts larger relative to body, stemapods more robust, T 1 apical scoli reduced to minutely spined humps, not situated on a projection as in all previous instars and not glossy as in terminal fifth or sixth instars. Colouration also as in fourth instar except saddle and lateral speckling darker and faint pink colouration present behind head anteriorly on T 1.
Sixth instar. (Figures 15c, d, 16b, 17a) Duration: Not recorded; body length 26–30 mm without stemapods, 37–40 mm with stemapods (n = 3). As for terminal fifth instar except slightly more robust and proportionally larger.
Pupa. (Figure 16d) Average duration: 22 days (n = 12). Length: ~ 16 mm (n = 1, female). As for A. argynnis but colouration dark brown (possibly due to older age of pupa), terminus of abdomen smooth except for small spines dorsally on A 10, otherwise A 10 less rugged than in A. argynnis.
Cocoon. (Figure 16e) As in A. argynnis.
Life history. Eggs were not observed in nature. In captivity eggs regularly hatch in the morning, generally between 8.00 and 10.00am. Larvae chew through but do not consume the entire egg chorion. First-instar larvae prefer very young foliage, specifically X. pseudosalzmannii leaves that are still red in colour and not fully developed, and due to the small size of these leaves, the larval resting positions depend on the shape and size of the leaf, on either the adaxial or the abaxial surface. As in the previous species, the larvae lay down a silken platform on the leaf surface and scrape the leaf surface to feed, leaving behind patches of skeletonised leaves. Unlike other species, larvae are quite restless, wandering to new leaves frequently, likely due to the small size of preferred leaf tissue per leaf. Due to the thinness of young X. pseudosalzmannii leaves, the skeletonisation of the leaves often cuts through the entire thickness of the leaf and so the larvae will feed on the margins of the holes cut in the leaf tissue. All subsequent instars feed from the edge of the leaf. Early third-instar larvae wander daily, stopping to feed occasionally and generally settling down to feed overnight, this daily cycle occurs until roughly halfway through the instar when the larvae become less restless and feed more consistently. Time spent in each instar and overall larval progression is slower than in previously discussed species. The fourth instar was observed to wander occasionally, but not as regularly as in the third instar. Some larvae undergo six instars, with the fourth and fifth instars of these larvae very similar to the fourth instar of larvae that undergo five total instars. Both terminal fifth and sixth instar larvae give rise to either male or female adults; thus, the number of instars was not indicative of sex. Larval behaviour is otherwise as for previous species except we noted that prepupal larvae were more regularly displaying characteristic wandering and darkening in colour in the morning rather than in the evening as in previous species. Cocoon building behaviour is also as in previous species.
One of the reared larvae made a cocoon that was opened before the adult eclosed. This allowed us to observe the hatching sequence in detail. The adult moth exits the pupa in the evening but takes nearly 2 h to exit the cocoon. We noted that the cocoon near the head of the moth became darker as it was dampened by a liquid released by the moth, the moth then rapidly exits the cocoon and fully expands its wings within minutes. Unlike previous species, all A. brasiliensis cocoons that had surviving pupae hatched within a few weeks of prepupal wandering behaviour, without any diapause during the summer.
In this species we observed a threat/feigning death display in the adult. A single female adult was found to lift its wings above its body, extend its legs anteriorly, and curl its abdomen under its thorax, similar in some ways to the display of Furcula spp. (Cerurinae) and some Saturniidae (St Laurent pers. obs). One adult female that was observed postemergence was apparently releasing pheromones after 11.30pm, but the end time of this behaviour was not documented.
Host plants. We reared a cohort of larvae on Xylosma pseudosalzmannii (Salicaceae). When Banara parviflora was offered, it was not accepted.
Distribution. We have restricted the type series of A. brasiliensis to material from the south-eastern Brazilian states of Paraná, Santa Catarina and Rio Grande do Sul, but it may be more widespread; see Remarks below.
Remarks. Specimens from other regions in Brazil, Paraguay and northern Argentina may also be this species but further work to determine the delimitation of the full distribution of A. brasiliensis outside of the small area we have defined is needed, especially considering that larval characters may be the best way to identify this species. Dissected material from Paraguay and Argentina in the USNM differs somewhat in the shape of the male VIII tergite, and there is more variability in the incidence of merged black lines along the forewing anal margin than what we see in south-eastern Brazil where this trait is more consistent. Schreiter (1943) reared and figured the larva and adult of a species belonging to the rarata species-group, found on Salix. He incorrectly referred to the species as ̍ Cerura argentina ̾, which is a synonym of Americerura argynnis. The larva he reared was from semi-arid Tucumán and the resulting adult is more lightly marked than specimens we have examined of A. brasiliensis, so we do not think it likely that they are conspecific. The larval illustration in Schreiter (1943) is not very detailed but it does not resemble A. brasiliensis larvae that we reared. Regardless, the association of a South American rarata species-group taxon with Salix is noteworthy and suggests that A. brasiliensis could also be found in association with that genus of plants in the future. Other records of the rarata species-group, including our own, are mostly from Xylosma and never Salix (Janzen and Hallwachs 2017; Miller et al. 2018).
The rarata species-group is wide-ranging in the Americas, and morphology is quite uniform across populations. However, considering some morphological consistencies in the south-eastern Brazilian population and the unique larval phenotypes observed in our rearing, we consider this population to be distinct enough to warrant specific treatment separate from other South American populations and certainly from the other named taxa belonging to this group from geographically distant locations in southern North America and Central America (A. rarata, Figure 19k and A. tehuacana (Draudt), Figure 19l) and Peru (A. rarata optima Bryk, a taxon not examined by the authors). Ideally, a complete taxonomic revision of the rarata group will be completed in which the Brazilian population can be further contextualised. Miller et al. (2018) stated that genetic differences separated up to three cryptic species in the rarata group in Costa Rica alone, none of which are conspecific with true A. rarata from Texas and Mexico. Ongoing genomic work suggests a wide range of cryptic diversity in this species group across the Americas (St Laurent unpublished).
description: Published as part of St Laurent, Ryan A., Carvalho, Ana Paula S., Orlandin, Elton & Carneiro, Eduardo, 2024, The life histories of Americerura (Lepidoptera: Notodontidae: Cerurinae) from southern Brazil, with the description of a new species, pp. 2039-2082 in Journal of Natural History 57 (45 - 48) on pages 2065-2077, DOI: 10.1080/00222933.2023.2282624, http://zenodo.org/record/10480185