Description of a new species and subspecies of Idalus Walker from Costa Rica, Honduras and Guatemala (Lepidoptera, Erebidae, Arctiinae, Arctiini)

Abstract A new species and subspecies of Idalus Walker are described from Costa Rica, Honduras and Guatemala. Images of males and females and their genitalia are provided. Locality information and distribution maps for Costa Rica and for Guatemala are included. The biology and phylogeny of Idalus are discussed.

introduction Walker (1855) described the genus Idalus based on the species Phalaena admirabilis Cramer from Surinam. Hampson (1901) provided a further description of the genus, and described only one additional species, with Rothschild subsequently describing nearly half the species currently placed in the genus (Watson and Goodger 1986). Travassos (1949) reviewed 19 species, comparing them to I. admirabilis from Amazonas and Southeastern Brazil as well as from Cayenne, French Guiana. The genus presently includes 50 species from the Neotropical region (Watson and Goodger 1986). Collecting in Costa Rica over the past 20 years has revealed 17 distinct species when compared to types in the British Museum of Natural History and the United States National Museum (B. Espinoza, unpublished). Some of these "species" appear to contain several sibling species as revealed by CO1 barcoding (D. H. Janzen, W. Hallwachs, B. Espinoza, unpublished;Janzen et al. 2009). This paper describes one of the distinct new species and compares it to populations with similar wing patterns found throughout Central America which also required that we name a new subspecies as well. The Arctiinae of our usage is the same as Arctiidae of earlier usage (Fibiger and Lafontaine 2005), with Idalus in the tribe Arctiini (Watson and Goodger 1986).

Materials and methods
Genitalia were prepared following procedures detailed by Lafontaine (2004). Photographs of adults and genitalia were taken with a Nikon CoolPix 4500, using a super micro lens. Samples of five specimens from Costa Rica and 24 from Guatemala were taken for DNA barcoding and sent to the Canadian Center for DNA barcoding in Guelph, Ontario. The resulting nucleotide sequences, a.k.a. "DNA barcodes" were compared with neighbor-joining trees using Kimura 2-parameter distances (methods in Ratnasingham and Herbert 2007).

Repository abbreviations INBio
Instituto Diagnosis. This species can be recognized by the four dark-brown horizontal stripes on the medial area of forewings, between vein Cu1 and the posterior margin together with the yellow medial area (Figs 1, 2), uncus with a bifid and U-shaped terminus in dorsal view, valve with the saccular margin lobulated in the middle (Figs 5a, 5b) and by its distinctive DNA barcode. It is very similar to Idalus maesi faustinoi, which has only three dark brown horizontal stripes on postmedial area of forewing.
Description. Adult male (Figs 1a,1b,5a,5b,5c). HEAD: Small head and large eyes; antennae serrate, base and antennae tip white, mid shaft brown; vertex slightly raised and hairy, yellow-orange; frons white with irregular mesial dark brown patch; labial palpi short and robust, upper half dark brown and lower half white; proboscis well developed. THORAX: Patagium white with red posterior edge and transverse yelloworange band; tegula white, red laterally with a stripe curving inward extending from the base to the apex; thorax robust, white, with two small and elongate dark brown anterior patches, two large, red mid-dorsal patches and two small dark brown rounded patches on the posterior margin, ventrally white, hairy and with a red, longitudinal and ventrolateral stripe below the wings; anterior coxae striped with red. Forelegs white, femur dark brown on the proximal surface, tibia double striped with dark brown from base to tips, tarsal segments brown on the anterior surface; middle legs white, femur with a dark brown patch on tips, tibia double striped with dark brown on the proximal half, tarsi white with brown irregularly on posterior surface; hind legs white, a dark brown patch at the junction of the femur and tibia, tarsi white with irregular brown on posterior surface. ABDOMEN: White ground color, dorsally red between terga 1 and 7, basal segment with an irregular patch of long white hair and a series of small white dots between terga 3 and 7; white ventrally. WINGS: Forewing length 20.4 mm (n = 10). Semihyaline, white ground color, a creamy-white triangular basal patch edged with brown and with four fine dark brown longitudinal lines between the costal margin and the anal vein; a small brown spot in the postbasal area running to the posterior margin; medial area with a large yellow-orange patch between anal margin and R1; a fine transverse dark brown line goes from the anal margin toward the costal margin and turns medially on it; a second parallel fine line, straight from the costal margin to the vein Cu1, then undulating from below it to the anal margin; on the costal margin and between the transverse lines, two very fine dark brown lines between the costal vein and R1 and four more stripes, one between Cu1 and Cu2, two between Cu2 and the anal vein and one between the anal vein and the posterior margin. Hindwing semihyaline white, expanded in humeral area. GENITALIA (Figs 5a,b,c): uncus elongate, slightly flattened dorso-ventrally and with an acute shape distally, on its dorsum a thin, longitudinal mesial ridge arising from near the base and almost reaching the tip, terminus bifid and U-shaped in dorsal view and with an acute edge. Valve sclerotized, very wide at the base, acute and slightly concave at the apex and with the saccular margin lobulated in the middle; a large lobe arising distally from the outer surface with a straight costal margin, the saccular margin lobulated in the middle and with a small and acute projection at the tip. Juxta convex, very slightly sclerotized but not well defined; transtilla membranous and very slightly sclerotized at the base of valvae; saccus short and V-shaped; aedeagus long, thin, curved ventrally in the anterior part and curved dorsally in the distal part; vesica short, with two basal diverticuli, one small lateral diverticulum on the right side and another in front projecting slightly ventrally and spinulose, distal portion of vesica with a large spinulose patch. Adult female (Figs 2a,2b,7). HEAD: antennae serrate but less so compared to male antennae; sensillae less dense and shorter in length compared to males. THORAX: markings as in male. ABDOMEN: markings as in male, but more robust and rounded at the tip. WINGS: Slight sexual dimorphism, with the only differences being that the shape and size of the female wing (forewing length: 22.8 mm (n = 04)), is broader and longer than that of the male, and the wing apices of the females are more rounded than in the males. GENITALIA (Fig. 7): Anal papillae flattened laterally and rectangular in lateral view with a dense patch of short setae dorso-laterally; posterior apophysis 2.5 x as long as anterior apophysis; ostium scle- rotized, very wide, dorsal margin rugose, ventral margin deeply concave and U-shaped; ductus bursae elongate, sclerotized and compressed dorsoventrally; corpus bursae oval, membranous and rugose with two small spiculate signa, one on each side the bursa; appendix bursa oval, slightly smaller than corpus bursa.
Distribution and biology. I. paulae has been collected between 1400 and 2230 m elevation in rain forest and the margins of cloud forest, on both Pacific and Atlantic slopes, from 1400 to 2230 m in the Cordillera Volcanica Central and the Cordillera de Talamanca of Costa Rica. There is a single specimen from the rain forest lowlands on the lowest slopes of the Cordillera Talamanca (100 m.) (Fig. 9). This is an unexpected locality but we are unable to find any differences between it and the remaining series of this species. Adults of I. paulae have been collected throughout the year but only in short series as the species is uncommon at lights and in light traps. No immature stages have been found but I. admirabilis, a related species, is known to feed on plants of the family Myrtaceae (Porto Santos et al. 2006). Etymology. This subspecies is named after Faustino René Camposeco López, a field technician of the Universidad del Valle de Guatemala, who with José Monzón helped collect the type series.

Idalus maesi faustinoi
Diagnosis. This subspecies is closely related to Idalus paulae which has four darkbrown horizontal stripes on postmedial area of forewings but can be distinguished by the three dark brown horizontal stripes distal to the yellow median area, between vein Cu1  (Figs 3, 4), uncus with a bifid and V-shaped terminus in dorsal view, valve with the saccular margin very slightly lobulated in the middle (Figs 6a, 6b) and by its distinctive DNA barcode. From Idalus maesi maesi it is easily recognized by it maculation patterns, in I. maesi maesi the basal and medial area of forewings, as well as patagium are white, the thorax has no red mid-dorsal patches and the basal abdominal segments are white. DNA barcode of I. maesi maesi and I. maesi faustinoi differ by 0.65%.
Description. Adult male (Figs 3a, 3b, 6a, 6b, 6c). HEAD: Head small and eyes large; antennae serrate, base and antenna tip white, mid shaft brown; vertex yelloworange, slightly raised and hairy; frons white with irregular mesial dark brown patch; labial palpi short and robust, upper half dark brown and lower half white; proboscis well developed; THORAX: Patagium white with a red posterior edge and transverse yellow-orange band; tegula white, red laterally and with a stripe curving inward extending from the base to near the apex; thorax robust, white, with two small, elongated dark brown anterior patches, two large, red mid-dorsal patches and two small dark brown rounded patches on the posterior margin, ventrally white, hairy and with a red, longitudinal and ventrolateral stripe below the wings; anterior coxae striped with red. Forelegs white, femur dark brown on the proximal surface, tibia double striped with dark brown from base to tips, tarsal segments brown on the anterior surface; middle legs white, femur with a dark brown patch on tips, tibia double striped with dark brown on the proximal half and with a small dark brown patch on tips, tarsi white with brown irregularly on posterior surface; hind legs white, a dark brown patch at the junction of the femur and tibia and at the junction of the tibia with the tarsi, tarsi white with irregular brown on posterior surface. ABDOMEN: White ground color, dorsally red between terga 1 and 7, basal segment with an irregular patch of long white hair and a series of small white dots between terga 3 and 7; white ventrally. WINGS: Forewing length 19.2 mm (n = 19). Semihyaline, white ground color, a creamy-white triangular basal patch edged with brown and with four fine dark brown longitudinal lines between the costal margin and the anal vein; a small brown spot in the postbasal area running to the posterior margin; medial area with a large yellow-orange patch between anal margin and R1; in the medial area, a fine transverse dark brown line goes from the anal margin toward the costal margin and turning medially on it; a second parallel fine line, straight from costal margin to the vein Cu1 and then undulating from below it to the anal margin; on the costal margin and between the transverse lines, two very fine dark brown lines between the costal vein and R1 and three more stripes, one between Cu1 and Cu2 and two between Cu2 and the anal vein. Hindwing semihyaline white, expanded in humeral area. GENITALIA (Figs 6a,b,c): uncus elongate, slightly flattened dorso-ventrally and acute distally, on its dorsum a thin, longitudinal mesial ridge arising from near the base and almost reaching the tip, terminus bifid and V-shaped in dorsal view and with acute edges. Valve sclerotized, very wide at the base, acute and slightly concave at the apex and the saccular margin very slightly lobulated in the middle; a large lobe arising distally from the outer surface with a straight costal margin, the saccular margin lobulated in the middle and with a very small, acute projection at the tip. Juxta convex, very slightly sclerotized but not well defined; transtilla mem-branous and very slightly sclerotized at the base of valvae; saccus short and V-shaped; aedeagus long, thin, curved downward ventrally in the anterior portion and upward dorsally in the distal part; vesica short, with two basal diverticuli, one small lateral diverticulum on the right side and another in front projecting slightly ventrally and spinulose, distal portion of the vesica with a large spinulose patch. Adult female (Figs  4a, 4b, 8). HEAD: antennae serrate but less so compared to male antennae; sensillae less dense and shorter in length compared to males. THORAX: markings as in male. ABDOMEN: markings as in male, but more robust and rounded at the tip. WINGS: Slight sexual dimorphism, with the only differences being that the shape and size of the female wing (forewing length: 22.2 mm (n = 5)), is broader and longer than that of the male, and the wing apices of the females are more rounded than in the males. GENI-TALIA (Fig. 8): Anal papillae flattened laterally and rectangular in lateral view with a dense patch of short setae dorso-laterally; posterior apophysis 2.5 x as long as anterior apophysis; ostium sclerotized, very wide, dorsal margin rugose, ventral margin deeply concave and V-shaped; ductus bursae elongate, sclerotized and compressed dorsoventrally; corpus bursae oval, membranous and rugose with two small spiculate signa, one on each side the bursa; appendix bursa oval, same size as corpus bursa. Distribution and biology. In Guatemala (Fig. 10) I. maesi faustinoi is reported from cloud forest at 1444 to 1616 m elevation (José Monzón personal comm.). A single female specimen from Honduras, Tegucigalpa is recorded from cloud forest at 2133 m. Adults have been captured throughout the year. No immature stages have been found but I. admirabilis, a related species, is known to feed on Myrtaceae (Porto Santos et al. 2006).
Comments. The Arctiinae (formerly Arctiidae) are estimated to have 11,000 species worldwide, with 6,000 species in the Neotropics (Watson and Goodger 1986). Some 20 years ago the Costa Rican fauna was estimated to be 350 species in 80 genera (INBio collections). At present there are an estimated 1,000 species in 215 genera in Costa Rica (INBio collections), which is remarkable given the small size of the country. Comparative DNA sequencing of the CO1 locus indicates that even more species are present (D. H. Janzen, W. Hallwachs, B. Espinoza, J. B. Sullivan, unpublished data).
According to Travassos (1949Travassos ( , 1950 Idalus species have a well-developed proboscis; short and upright labial palpi with the third segment tiny; antenna serrate in both sexes; elongate wings; forewing venation with Sc ending before the apex of wing, R1 arising from discal cell and ending before reaching the apex of wing, R2 and R3 ending before the apex of wing, R4 ending on the apex, R5 ending after apex, M1 arising from anterior angle of discal cell, M2 and M3 arising from posterior angle of discal cell, Cu1 arising from near the posterior angle of discal cell, Cu2 arising from the distal third of the cell, anal vein ending on tornus; hindwing venation with Sc arising from the distal half of cell and not reaching the costal margin of wing, R arising from anterior angle of cell, M and Cu1 arising from posterior angle of cell, Cu2 arising from the distal half of cell, A1 ending before reaching tornus and A2 ending on tornus. The newly described taxa I. paulae and I. maesi faustinoi are consistent with these characters. DNA barcoding and neighbor-joining analyses (Ratnasingham and Hebert 2007) of almost all the species of Idalus in Costa Rica (I. aleteria (Schaus), I. carinosa Schaus, I. crinis Druce, critheis Druce, I. dares Druce, fasciipuncta Rothschild, I. herois Schaus, I. perlineosa Rothschild, I. tuisiana Schaus, I. tybris (Cramer), I. veneta Dognin, I. borealis (Rothschild), I. vitrea (Cramer), I. vitreoides (Rothschild), plus several unnamed species) group them in two groups that appear to be related groups. I. paulae, I. maesi maesi (Laguerre, 2006) and I. maesi faustinoi form a related group to I. admirabilis, I. crinis and I. herois. The caterpillars of this latter group of three species is known to eat foliage of Myrtaceae (Porto Santos et al. 2006), (D. H. Janzen and W. Hallwachs, unpublished). The admirabilis-maesi groups make up one of the primary branches of Idalus. The other primary branch divides into a vitrea group and a perlineosa group. I. borealis is in the vitrea group and caterpillars have been found feeding on Combretaceae (Combretum) (D. H. Janzen and W. Hallwachs, unpublished). I. perlineosa and a likely undescribed sibling species both in the perlineosa group feed on Proteaceae (Roupala) (D. H. Janzen and W. Hallwachs, unpublished). Interestingly, while maculation patterns vary widely in the genus, these patterns unlike the foodplant associations, do not cluster cleanly among the four groups. The color patterns included by Travassos in his admirabilis group sort into all four barcode groups.
I. paulae differs from I. maesi maesi and I. maesi faustinoi in DNA sequence of the CO1 locus by approximately 5%. I. maesi maesi and I. maesi faustinoi differ by at least 1% but I. maesi faustinoi breaks into two groups differing by 0.65%. I. maesi maesi clearly differs from I. paulae and I. maesi faustinoi in maculation (the median yellow area is white) but does not appear to differ in male and female genitalia (M. Laguerre, personal communication). Geographically, I. maesi maesi occurs in the mountains of northern and southern Pacific Nicaragua, I. paulae in the mountains of Costa Rica, and I. maesi faustinoi in the mountains of Honduras and Guatemala. The two distinct haplotype groupings of I. maesi faustinoi may represent two taxa but because they seem to have identical maculation and genitalia and because they do not sort geographically, we have chosen not to name both groups. Instead, the holotype and paratypes are based on populations from the northern montane slopes in Guatemala. It will take additional studies to resolve the haplotype distributions and to establish the food plants upon which this group feeds.
We have not tried to establish morphological characters that separate the maesi group from the other three Idalus groups. However, we have noticed that in the maesi group, sexual modifications of scales and venation in the area of wing overlap are absent but present in those species we have examined from the other three groups. The humeral area is lobed but that character applies to most Arctiinae. The small differences in the CO1 sequences between I. maesi maesi and I. maesi faustinoi may reflect recent and rapid evolution of these species in the complex montane regions of Central America.