Rheumaptera mochica (Dognin, 1904) (Lepidoptera, Geometridae, Larentiinae) is reported from Chile for the first time. It was described from the western slopes of the Andes of southern Peru more than 100 years ago, and was recently rediscovered in Chile after larvae were collected and reared on the shrub Senna birostris var. arequipensis (Meyen ex Vogel) H.S. Irwin & Barneby (Fabaceae). This discovery expands the known distribution of this moth and provides its first host plant record. The genitalia of R. mochica are described and illustrated for the first time and compared to those of R. affirmata (Guenée, [1858]). A maximum likelihood analysis based on mitochondrial DNA sequences clustered R. mochica as sister to R. affirmata with 3.6–3.8% divergence (K2P). A lectotype is designated for Calocalpe mochica Dognin, 1904.

DNA barcodes, Fabaceae, genitalia, Rheumapterini, Senna birostris

Rheumaptera Hübner, 1822 (Lepidoptera, Geometridae, Larentiinae) is a widespread moth genus with 66 species, mostly from the Palearctic and Oriental regions; 14 species are recorded in the Western Hemisphere (Parsons et al. 1999). A recent molecular phylogenetic analysis strongly supports its monophyly and resulted in the transfer of three New World species from Coryphista Hulst, 1896 and Triphosa Stephens, 1829 to Rheumaptera (Brehm et al. 2019).

The Neotropical Rheumaptera mochica (Dognin, 1904) was originally described in Calocalpe Hübner, [1825], a junior synonym of Rheumaptera (Parsons et al. 1999). The species was based on two syntypes, a male and a female, from Arequipa on the western slopes of the Andes in southern Peru (Dognin 1904). No additional specimens have been reported in the literature since its original description. However, recently, adults of R. mochica were reared from larvae collected on a native shrub in northern Chile, a discovery that sheds light on this obscure geometrid moth.

The goals of this study were to confirm the identity of the reared adults, describe and illustrate their genitalia, and analyze their DNA from the COI barcode region (sensu Hebert et al. 2003) for the first time. Also, we report the host plant of R. mochica for the first time and expand its known distribution range. We designate a lectotype for Calocalpe mochica Dognin, 1904, to stabilize its nomenclature.

The moth family Geometridae is more species-rich in the Neotropical Region than in any other (Brehm et al. 2016; 2019). More than 6400 species have been described from the Neotropics (Scoble et al. 1995), many of which are known only from their type material. The specimens of R. mochica from northern Chile are the first to be reported in the literature after more than one hundred years since this species was described by Dognin (1904).

The wing pattern of R. mochica is similar to that of the syntype of R. affirmata (Fig. 15). The subterminal line could be a diagnostic character to separate the two species, as this is absent or slightly differentiated in R. mochica (Figs 1–4), whereas this line is well-differentiated and creamy white on the fore- and hindwing of R. affirmata. However, additional specimens of these two Neotropical species must be examined to more accurately characterize their wing pattern, because high intraspecific variation occurs in Holarctic representatives of Rheumaptera (McGuffin 1973).

Figure 15. 

Rheumaptera affirmata (Guenée, [1858]), Brazil, syntype (dorsal, ventral) and labels. Photos kindly provided by Gunnar Brehm. Scale bar: 10 mm.

Genitalia morphology provides important characters for the identification of species of Rheumaptera and related genera (McGuffin 1973; Wanke et al. 2019). But the genitalia of R. mochica had remained a mystery since the species was described. The genitalia of both sexes are here described and illustrated for the first time; they are very similar to those of R. affirmata (Figs 16–18) based on Brazilian specimens from the DZUP collection. However, the two species can be accurately identified and separated based on morphology of the genitalia. In the male of R. mochica, the sacculus projection is strongly curved distally and has a small basal process, and the vesica has spine-like cornuti the longest of which is slightly shorter than half the phallus length. In contrast, the male of R. affirmata has the sacculus projection only slightly curved and lacks a basal process, and the vesica has serrated cornuti the longest of which is slightly shorter than a quarter of the phallus length. In the female of R. mochica, signa are mainly concentrated near the middle of the posterior part of the corpus bursae, whereas in R. affirmata signa are mainly concentrated on the anterior half of the posterior part of the corpus bursae.

Figures 16–18. 

Rheumaptera affirmata (Guenée, [1858]), Brazil, genitalia 16 male genitalia in ventral view, phallus removed 17 phallus 18 female genitalia, ventral view. Scale bar: 1 mm.

This preliminary assessment of R. mochica provides a few interesting results, although the molecular analysis presented here was based on a single mitochondrial marker. First, R. mochica is confidently recovered as a member of Rheumaptera as proposed by Parsons et al. (1999). Second, R. affirmata was found to be the nearest congener to R. mochica, in agreement with genitalia morphology. Third, the transfer of three New World species to Rheumaptera, R. affirmata, R. pallidividata (Snellen, 1874), and R. meadii (Packard, 1874), based on a multilocus molecular analysis (Brehm et al. 2019), was supported in our analysis. Clearly, analysis of additional molecular markers and a more complete taxon sampling would provide a more robust reconstruction of the phylogenetic relationships of R. mochica and its congeners.

Host plants remain unknown for most species of Rheumaptera. Available records indicate that their host ranges can be remarkably wide, such as in the Holarctic R. hastata (Linnaeus, 1758) and R. subhastata (Nolcken, 1879), whose larvae feed on plants of at least three families (McGuffin 1973; Hausmann and Viidalepp 2012) or are restricted to a single plant genus, such as in R. affirmata, whose larvae feed on at least two species of Vicia (Fabaceae) in the Neotropics (Brehm 2002). Senna birostris var. arequipensis is the first, and only, host plant ever recorded for R. mochica. The first author searched for geometrid larvae on other native plants in the vicinity of Senna sp. at the study site, including other representatives of Fabaceae (Vargas et al. 2020; Vargas 2021), but larvae of R. mochica were not found.

The discovery of R. mochica in northern Chile expands the previously documented distribution range of this geometrid moth by about 300 km to the south-east. The geographic distribution of its host plant is from southern Peru to northern Chile at elevations between 2200 and 3900 m (Irwin and Barneby 1982), encompassing the localities of the type specimens of R. mochica and those newly reported here.

Previous Chilean records of Rheumaptera were restricted to the southern zone of Chile (Parsons et al. 1999). Five species have been recorded from the rainforests of northern Patagonia at about 42°S in southern Chile (Hausmann and Parra 2009). In contrast, R. mochica is the first species of the genus recorded in the extremely arid environments of the northernmost part of the country. This discovery suggests that, despite their remarkable aridity, these harsh environments may harbour more undiscovered or obscure, native geometrid moths whose biology deserves further attention.

We thank Olaf H. H. Mielke (Universidade Federal do Paraná, Brazil) for the loan of the R. affirmata specimens for dissection, Wilson Huanca-Mamani for the use of the molecular biology equipment, and Ben Proshek, Systematic Entomology Laboratory, ARS, USDA, for dissection and photography of the type specimens. We thank the reviewers Daniel Bolt and Axel Hausmann, who provided kind, helpful comments on the manuscript, and Subject Editor Gunnar Brehm for kindly sharing photos of the syntype of R. affirmata (Fig. 15) deposited in the Natural History Museum (NHMUK), London, UK. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by USDA. USDA is an equal opportunity provider and employer. This study was supported by project UTA-MAYOR 9729–21.