Native Myrtaceae in Brazil are damaged by defoliating caterpillars, which can migrate to important crops such as exotic Eucalyptus spp. (Zanuncio et al. 1993, Oliveira et al. 2000). Lepidoptera defoliators of Eucalyptus species in Brazil include native moth species such as Eupseudosoma aberrans (Schaus 1905) and Eupseudosoma involuta (Sepp 1855) (Lepidoptera: Erebidae), Automeris sp. (Walker) and Eacles imperialis (Walker 1856) (Lepidoptera: Saturniidae), Oxydia vesulia (Cramer 1779), Sabulodes caberata (Guenée 1857) and Thyrinteina arnobia (Stoll 1782) (Lepidoptera: Geometridae) (Zanuncio et al. 1998, Soares et al. 2009a).

Fig. 1.

Euselasia hygenius occulta (Lepidoptera: Riodininae); Ventral view of female (A); dorsal view of female (B); ventral view of male (C); dorsal view of male (D). Viçosa, Minas Gerais State, Brazil.

Insects can expand their host plant range onto nonnative agricultural plants that have been introduced as reported for tropical crops such as cocoa (Theobroma cacao), sugarcane (Saccharum officinarum), tomato (Solanum lycopersicum)(Leite et al. 2001) and eucalyptus (Eucalyptus spp.) (Strong 1974, Oliveira et al. 2005, Soares et al. 2009b). Caterpillars of the genus Euselasia spp. feed on Eucalyptus spp. and on Eugenia pitanga, Eugenia uniflora, Psidium grandifolium and Psidium guajava (Myrtaceae), their natural hosts (Silva et al. 1968). Euselasia eucerus (Hewitson 1982) (Lepidoptera: Riodininae), reported as Euselasia apisaon, was collected in an Eucalyptus sp. plantation in the Vale do Rio Doce and Zona da Mata regions of Minas Gerais State, Brazil (Zanuncio et al. 2009). Eggs of Euselasia apisaon (Dahman 1823) (Lepidoptera: Riodininae) were collected in plantations of Eucalyptus grandis (Myrtaceae) in Belo Oriente, Minas Gerais State, Brazil (Murta et al. 2008). Euselasia mys lara (Stichel 1919) (Lepidoptera: Riodininae) was reported feeding on plants of P. guajava in Viçosa, Minas Gerais State, Brazil. The inclusion of this species in monitoring programs of Eucalyptus spp. was recommended due to the phylogenetic proximity of these host plants (Soares et al. 2009b).

A basic understanding of host plant diet breadth is critical to understanding population dynamics of native lepidopterans and for modeling the probability that a species of Lepidoptera might extend its feeding to an exotic plant species (Murta et al. 2008, Zanuncio et al. 2009). The objective of this study was to identify a Lepidoptera feeding on P. guajava at the Federal University of Viçosa in Viçosa, Minas Gerais State, Brazil.

First instar caterpillars of a lepidopteran were observed on the underside of P. guajava leaves in August 2009 at the campus of the Federal University of Viçosa in Viçosa, Minas Gerais State, Brazil (South Latitude of 20° 45′14″ and West Longitude of 42º 52′55″ and altitude of 648 meters). Leaves of P. guajava with caterpillars were detached from the plant, packed in plastic containers and taken to the Laboratory of Biological Control of Insects of the Institute of Biotechnology Applied to Agriculture (BIOAGRO) where they were kept at 25 ± 2° C, 70 ± 5% relative humidity and photoperiod of 12 hours. These leaves were changed daily until adult emergence. Adults were killed in a killing chamber, wrapped in an entomological blanket and sent to Dr. Olaf Hermann Hendrik Mielke of the Federal University of Paraná in Curitiba, Paraná State, Brazil for identification.

Insects were identified as Euselasia hygenius occulta Stichel 1919 (Lepidoptera: Riodininae). Its larvae are gregarious and feed, rest, molt, and pupate synchronously. This species has five instars with processionary behavior throughout its development. Caterpillars range in color from yellow during early instars to dark brown at the final instars with six longitudinal white stripes, two on the back, and two on each side. The head is orange and strongly sclerotized and caterpillars have many setae dorsally on all segments. Adults of this species exhibit sexual dimorphism. Females are pale gray dorsally and gray ventrally, abdomen prominent and 2.5 cm wingspan wings. Males are dark gray ventrally and dorsally black with 2.7 cm (Fig. 1). Adults of both sexes show a “V” at the front view of the head.

This species had been cited in monitoring programs in tropical forests and savanna areas with traps, but without its host plants being specifically identified (Emery et al. 2006, Bonfantti et al. 2009). Thus, this is the first report of E. hygenius occulta feeding on P. guajava anywhere. Aside from the observations here, the habitat and host plants of different species of the genus Euselasia spp. are poorly known (Callaghan et al. 2007).

Immature stages of E. hygenius occulta present morphology and behavior similar to those of other species of this genus such as Euselasia chrysippe (Bates 1866) and Euselasia bettina (Hewitson 1869) (Lepidoptera: Riodininae), but with shorter larva stadium and apparent absence of the sixth instar stage (Nishida 2010).

Euselasia hygenius occulta adults differ from other species such as E. hygenius by its sexual dimorphism (Zanuncio et al. 1995). Adults of the latter species do not show dimorphism. In both male and females the front and rear wings are black dorsally. Euselasia eucerus, reported as E. apisaon, also shows sexual dimorphism, but the dorsal surface of male wings has red brick color with dark edges on both pairs. Females of this species are dark gray and sometimes exhibit three pairs of white circular spots in the middle of the forewing (Zanuncio et al. 1990). Euselasia mys lara has accentuated sexual dimorphism. The dorsal of both pairs of wings of males are black with dark red spots, that begin near the chest and radiate to the edge of wings. These spots are absent in females. Males of E. mys lara have an average wingspan of 3.0 cm and females 2.6 cm (Soares et al. 2009b).

The abundance of species of Euselasia spp. in Brazil and reports of E. eucerus feeding on Eucalyptus spp. plants show that other species of this butterfly genus could also damage this plant as a result of selection pressure in extensive forest plantation areas (Soares et al. 2009b). This is important because other Lepidoptera such as T. arnobia, the main defoliator of Eucalyptus spp. in Brazil (Oliveira et al. 2005, Soares et al. 2009a,c) has often being reported causing economic damage in this culture. Euselasia hygenius occulta should be included in monitoring programs of P. guajava pests and Eucalyptus spp. due to its potential migration to plants of this last genus.