Information on host plants of lepidopterans is extremely important for a comprehensive understanding of the ecology and evolution of these insects (Robbins & Aiello 1982). Although a renewed interest in the biology and systematics of Neotropical Lycaenidae is evident in recent literature (Duarte et al. 2001; 2005; Robbins & Busby 2008; Duarte & Robbins 2010; Silva et al. 2011; Bächtold et al. 2013; Kaminski et al. 2013; Robbins & Glassberg 2013), their host plants remain insufficiently known.

About 50 butterfly species have been recorded from the arid landscapes of northern Chile (Peña & Ugarte 1996). In addition to their low diversity, life histories of these butterflies are scarcely documented. Host plant records are available for the larvae of some species (Benyamini 1995; Peña & Ugarte 1996; Vargas & Parra 2009; Vargas 2012, 2013), but remain undocumented for many representatives of this fauna, despite that an adequate knowledge of these relationships is critical to understand the distribution and abundance of the butterflies inhabiting these extremely arid environments (Vargas & Lamas 2011; Vargas & Benítez 2013).

Thaeides Johnson, Kruse & Kroenlein, 1997 (Lepidoptera, Lycaenidae, Theclinae, Eumaeini) is a poorly known montane Neotropical genus composed of 5 valid species (Robbins 2004). Thaeides theia (Hewitson, 1870) is the most widespread species of the genus, ranging from southeastern Mexico to Bolivia and southeastern Brazil (Warren et al. 2012). In Colombia it has been found occasionally on hilltop landscapes of the western and eastern Andes (Prieto & Dahners 2006; Salazar 2010). Despite the broad geographic range of T. theia, its trophic relationships remain unknown.

Thaeides muela (Dyar, 1913) is the only representative of the genus in Chile (Peña & Ugarte 1996), where records indicate that it is restricted to the northernmost area of the country at about 3,500 m asl (Johnson 1992; Benyamini 1995; Peña & Ugarte 1996), a region characterized by a tropical xeric bioclimate (Luebert & Pliscoff 2006). The species also occurs in Ecuador and Peru (R. K. Robbins in litt. 15 Oct 2013).

The behavior and life history of T. muela remain largely unknown. The only information available is based on notes of this butterfly lingering around Baccharis (Asterales: Asteraceae) bushes (Benyamini 1995), and among Escallonia angustifolia K. Prest (Escalloniales: Escalloniaceae) and Baccharis santelisis Philippi along the Chilean range (Peña & Ugarte 1996). Benyamini (1995) suggested that eventual locations of this hairstreak and other rarely collected Lycaenidae might be discovered through detection of certain frequently sympatric and more common indicator species, such as Pyrgus bocchoris trisignatus (Mabille, 1876) (Hesperiidae) and Teriocolias zelia andina Forbes, 1928 (Pieridae). In addition, Peña & Ugarte (1996) indicated that even though adults may be found relatively easily during certain months of the year, their rapid flight pattern complicates field observation.

In Dec 2009, as part of a preliminary survey of lepidopteran larvae associated with the native vegetation, one florivorous lycaenid larva was found eating actively on an inflorescence of the native shrub Baccharis alnifolia Meyen & Walp. in the neighboring area of the Zapahuira village, Parinacota Province, in the northern Chilean Andes. The larva was transported to the laboratory in a plastic vial, where additional inflorescences of the plant were periodically offered until pupation, which occurred approximately 12 days after collection. A male adult emerged in Jan 2010, and was identified as T. muela, based on the original description and specimens deposited at the National Museum of Natural History, Washington, DC, USA. Additional larvae eating on the inflorescences of B. alnifolia were collected in Aug 2011 and Nov 2012 in 2 other localities of Parinacota Province: Putre and Socoroma. Five adults were obtained from this laboratory rearing.

Baccharis alnifolia is the first host plant recorded for T. muela. Moreover, the present paper is also the first to mention the host plant and florivory for the genus Thaeides. Apparently florivory is a widespread feeding behaviour among larvae of Neotropical Eumaeini (Silva et al. 2011). Interestingly, only 4 host plant records for Neotropical Lycaenidae involving the highly diversified genus Baccharis were available, all these in Eumaeini: Baccharis punctulata DC for Rekoa palegon (Cramer, 1780) (Monteiro 1991), Bac charis sp. for Rekoa malina (ex-larvae; adults deposited at Universidade Federal do Paraná/ UFPR, Curitiba, Brazil), Baccharis dracunculifolia DC for Laothus phydela (Hewitson, 1867) (unpublished manuscript of C. M. Biezanko kindly lent by O.H.H. Mielke, UFPR), and Baccharis latifolia (Ruiz et Pav.) Pers. for Rhamma arria (Hewitson, 1870) (Bodner 2011).

Silva et al. (2011) indicated that most of the florivorous Eumaeini of the Brazilian Cerrado are polyphagous or oligophagous. Furthermore, polyphagy can be encouraged in ecosystems where plant reproduction is facilitated by climatic conditions throughout the year (Monteiro 1991). Baccharis is well represented along the Andes. Unfortunately, no data are available about the specificity of larval host use by T. muela. Thus, additional studies will be necessary in order to determine the host range of this poorly known Neotropical hairstreak along the arid landscapes of the northern Chilean Andes.

An accurate determination of the host range is an important aspect for ecological studies of Lycaenidae (Bächtold et al. 2013). There are few records of Asteraceae as host plants for larvae of Eumaeini, a subject discussed at length by Fiedler (1991). It is remarkable to note that Asteraceae, one of the largest groups of angiosperms, is still rarely cited as host plants for these butterflies (a comparison with nymphalid butterflies is possible in Beccaloni et al. 2008). Fiedler (1991) suggests that the lycaenids may have diversified by keeping their primary association with certain plant groups (mainly representatives of Asterales) and by sporadically using unrelated taxa with chemical similarities. As pointed out by Fiedler (1991), it is also possible to think that the larvae of other families and subfamilies of butterflies may have occupied many potential niches in the most recent angiosperm taxa (e.g. Asteraceae), and that has prevented the wider use of these plants as larval host plants of Lycaenidae.

Association of lycaenid larvae and/or pupae with ants, i.e. myrmecophily, is a widespread phenomenon among Lycaenidae that ranges from facultative to obligate (Fiedler 1991, 1995). Generally myrmecophilous larvae possess functional glandular organs (Ballmer & Pratt 1991; Fiedler 1995). None of the 6 larvae collected in this survey was attended by ants in the field. Unfortunately, functional nectary glands were not searched on these larvae. Thus, additional samplings and field observations are needed to verify if myrmecophily is involved in the life history of T. muela.

Vouchers will be deposited in the Museo Nacional de Historia Natural de Santiago, Santiago, Chile (MNNC) and in the Colección Entomológica de la Universidad de Tarapacá, Arica, Chile (IDEA).

Summary

The native shrub Baccharis alnifolia Meyen & Walp. (Asterales: Asteraceae) is recorded as the first larval host plant known for the Neotropical hairstreak Thaeides muela (Dyar, 1913) (Lepidoptera, Lycaenidae, Eumaeini), based on field samplings performed on the western slopes of the northern Chilean Andes.

Key Words: Andes, Asteraceae, Baccharis, caterpillar, Florivory

Resumen

El arbusto nativo Baccharis alnifolia Meyen & Walp. (Asterales: Asteraceae) es mencionado como el primer registro de planta hospedera para la mariposa neotropical Thaeides muela (Dyar, 1913) (Lepidoptera, Lycaenidae, Eumaeini), sobre la base de colectas efectuadas en la vertiente occidental de los Andes del norte de Chile.

Palabras Clave: Andes, Asteraceae, Baccharis, florivoría, larva