The moth Citioica anthonilis (Herrich-Schaeffer, ) (Lepidoptera: Saturniidae: Ceratocampinae) occurs in areas of preserved forests, where it is a significant defoliator of Piptadenia gonoacantha (Martius) Macbride (Fabaceae) trees. In this study, caterpillars of fourth instar C. anthonilis were collected from the ground after falling from a P. gonoacantha tree in a herbarium and were reared in the laboratory. Pupae of C. anthonilis, the velvetbean caterpillar Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae), and the flour beetle Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae) were each parasitized by mated parasitoid females wasp Palmistichus elaeisis Delvare & LaSalle, 1993 (Hymenoptera: Eulophidae). Data were collected relating to the levels of parasitism and emergence rates of P. elaeisis per host pupa, and the size of the host pupae. Our results show that the fecundity of P. elaeisis was highest in C. anthonilis hosts, probably because of the greater size of these pupae, which supported the development of an increased number of parasitoids. Therefore, C. anthonilis is a suitable host for rearing P. elaeisis in the laboratory, which could be a means of rearing parasitoids for the biological control of this defoliator of P. gonoacantha and other pests in Brazil.
Citioica anthonilis (Herrich-Schaeffer, ) (Lepidoptera: Saturniidae: Ceratocampinae) occurs in Central America, Guyana, Amazonia, the Andean region from Mexico to Bolivia and southern Brazil, in tropical forests with an annual rainfall of between 250 mm and 2500 mm, and is a bioindicator of habitat conservation (Regier et al. 2008, Stefanescu et al. 2009). Citioica anthonilis completes its larval development on Robinia pseudoacacia L. (Fabaceae) and Salix caprae L. (Salicaceae); its larvae are green in color with a black stripe on each side (Prestes et al. 2009). The length of the forewing C. anthonilis females collected in Iraí, Rio Grande do Sul State, Brazil (Atlantic Forest biome) was 36–43 mm, in contrast to that of the male, which was 26–31 mm long; the flight period of this insect is January in this region (Prestes et al. 2009).
The parasitoid wasp Palmistichus elaeisis Delvare & LaSalle, 1993 (Hymenoptera: Eulophidae) is an important natural enemy of pests on palms (Arecaceae), eucalyptus (Myrtaceae), passion fruit (Passifloraceae) and Terminalia catappa L. (Combretaceae) (Gil-Santana & Tavares 2006, Pereira et al. 2011, Tavares et al. 2012a), attacking the pupae of lepidopteran defoliators (Delvare & LaSalle 1993, Pereira et al. 2010a, Tavares et al. 2012b). Importantly, it can also be reared in the laboratory on alternative lepidopteran and coleopteran host pupae (Zanuncio et al. 2008, Pereira et al. 2009, 2010b), including those of species of the genus Hylesia Hübner,  and Dirphia moderata Bouvier, 1919 (Lepidoptera: Saturniidae) (Pereira et al. 2008, Soares et al. 2009).
The objective of this study was to assess the suitability of alternatives hosts for rearing P. elaeisis in the laboratory. We used pupae of its natural host, C. anthonilis, and also of the velvetbean caterpillar Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae), and the flour beetle Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae). We recorded the rates of parasitism, and emergence of P. elaeisis from pupae of these species, as well as the length and width of each host pupa.
Materials and Methods
On May 4, 2011, 25 fourth-instar caterpillars of C. anthonilis were collected from the ground after falling from a Piptadenia gonoacantha (Martius) Macbride (Fabaceae) tree in the herbarium of the Federal University of Viçosa (UFV) in Viçosa, Minas Gerais State, Brazil (20°45′S, 42°51′W, 651 m above sea level; Atlantic Forest biome) (Tavares et al. 2011a). The occurrence of P. gonoacantha is widespread throughout the Atlantic Forest biome of Brazil (Marques et al. 2009, Braga et al. 2011). The caterpillars were brought to the Laboratory of Biological Control of Insects (LCBI) from UFV and kept at 25 ± 1°C, under a 12-h photoperiod and 70 ± 10% relative humidity (RH) in 1L plastic cups with a thin layer of sand in the bottom and P. gonoacantha branches until they pupated, which occurred on May 10 and 11, 2011.
In total, 20 newly formed C. anthonilis pupae were each placed in a test tube (14 cm length × 2.2 cm diameter) closed with a cotton swab and kept for 10 days with 40 mated P. elaeisis females of a first generation emerged from pupa of Thagona tibialis Walker, 1855 (Lepidoptera: Lymantriidae). This number of females was used based on results of a preliminary test using 10, 20, 30, 40 or 50 P. elaeisis females per C. anthonilis pupa. Pupae of T. tibialis had been collected from a T. catappa tree in the campus of UFV (Tavares et al. 2012a, 2012b). A drop of honey was placed inside the test tubes as food for the parasitoid females. Recordings were made of the rates of parasitism and emergence, as well as the number of parasitoids that emerged per P. elaeisis pupa. In addition, the width and length of each C. anthonilis pupa were recorded.
To study the parasitism by P. elaeisis of A. gemmatalis and of T. molitor, 20 newly formed pupae of each host species were each placed in a test tube (14 cm length × 2.2 cm diameter) for 48 hours with six mated P. elaeisis females, based on the methodology proposed for A. gemmatalis (Pereira et al. 2010c) and T. molitor (Zanuncio et al. 2008). The pupae were obtained from the mass rearing of these insects from the LCBI of the UFV (Pereira et al. 2010b, Zanuncio et al. 2011). The same data recordings were made as for C. anthonilis detailed above.
The parasitism of C. anthonilis, A. gemmatalis and T. molitor pupae by P. elaeisis was evaluated according to the following criteria: parasitized pupae turned caramel in color, whereas unviable pupae were black in color, lost weight, became hollow and then died and nonparasitized pupae had emergence of adult (Zanuncio et al. 2008, Pereira et al. 2010c). The design was entirely randomized with three treatments represented by C. anthonilis, A. gemmatalis and T. molitor. Each treatment had 20 replications. Data of the mean ± standard error of mean of parasitism and emergence rates were obtained. Data relating to the number of parasitoids of P. elaeisis that emerged per host pupa, and the width and length of the pupae were submitted to Analysis of Variance (ANOVA) and the means (± standard error of mean) compared between species by Tukey test at 5% probability, using the software Statistical Analysis Software (SAS/STAT 1989) (Supplier: UFV).
Adult females of P. elaeisis were photographed in the UFV. These pictures were sent to the Department of Biology of Lund University in Sölvegatan, Lund, Sweden for identification by Dr. Christer Hansson. Five pupae of C. anthonilis were kept in plastic cups until adult emergence. Four adult females were sent to the Department of Zoology of Federal University of Paraná in Curitiba, Paraná State, Brazil for identification by Dr. Olaf Hermann Hendrik Mielke. Second (Fig. 1), fourth (Fig. 2) and fifth instar (Fig. 3) caterpillars, and adult (Fig. 4) C. anthonilis were photographed by Leroy Simon and these pictures are available at http://www.silkmoths.bizland.com/phlsimon.htm.
Pupae of C. anthonilis were longer (3.82 ± 0.28 cm) and wider (0.8 ± 0.04 cm) than those of A. gemmatalis (1.68 ± 0.19 cm and 0.67 ± 0.02 cm, respectively), which, in turn, were longer and wider than those of T. molitor (1.47 ± 0.12 cm and 0.59 ± 0.01 cm, respectively) (F2,57; P <0.05 in both cases).
In total, P. elaeisis parasitized 100% of C. anthonilis pupae, 90% of T. molitor pupae and 70.0% of A. gemmatalis pupae. The same values applied to the emergence of P. elaeisis from the pupae of each species (i.e. parasitoids emerged from each of the pupae that had been parasitized).
More P. elaeisis emerged per C. anthonilis pupa (286 ± 29 insects) than from A. gemmatalis pupae (108 ± 17 insects), totals that were both higher than from T. molitor pupae (69 ± 7 insects) (F2,57; P <0.05).
This is the first report of the parasitism of C. anthonilis pupae by P. elaeisis in the laboratory. The parasitism of C. anthonilis by progeny of P. elaeisis collected from T. tibialis pupa sampled from T. catappa trees in Viçosa confirms the ability of a wild strain of P. elaeisis to parasitize C. anthonilis pupae in the laboratory. However, wild strains of parasitoids might require several generations in the laboratory to develop an adequate parasitic ability on alternative hosts, including P. elaeisis collected in the field in Viçosa on pupae of A. gemmatalis, Bombyx mori Linnaeus, 1758 (Lepidoptera: Bombycidae) and Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae) (Pereira et al. 2010b, 2011).
Parasitism of C. anthonilis pupae by P. elaeisis suggests that this host is suitable for rearing this parasitoid in the laboratory. The occurrence of C. anthonilis in preserved areas of native forests in several States and in the Federal District of Brazil and the adaptation of P. elaeisis and other hymenopteran parasitoids in urban areas to T. catappa and to plantations of crop species from the Arecaceae, Myrtaceae and Passifloraceae suggests the need to maintain areas of original vegetation near agricultural and forest crops to increase natural biological control (Woodcock & Vanbergen 2008, Pickett et al. 2009), particularly by eulophid parasitoids on pupae of arctiid, geometrid, lymantriid, noctuid and saturniid defoliators (Murakami & Hirao 2010). This was shown by fewer outbreaks of lepidopterous pests on Eucalyptus grandis Hillex Maiden (Myrtaceae) plantations near areas of native forest due to the refuges for natural enemies (Zanuncio et al. 2001). Natural enemies might be more frequent in mixed environments, as plants of Crotalaria juncea L. (Fabaceae) grown near to Zea mays L. (Poaceae) act as a refuge for these organisms and so aid the natural biological control of herbivores of this important crop (Tavares et al. 2011b, 2012c, 2012d).
As in our investigation, more individuals of P. elaeisis have been recorded to emerge per C. anthonilis pupa than from T. molitor pupae in other studies [only 71 individuals (Zanuncio et al. 2008)] or from pupae of Thyrinteina leucoceraea Rindge, 1961 (Lepidoptera: Geometridae) [only 194 individuals (Pereira et al. 2008)]. This can be explained by the larger size in terms of length and width of C. anthonilis pupae compared with those of T. molitor, T. leucoceraea and A. gemmatalis. Pupae of B. mori, which are of a similar or larger size to those of C. anthonilis, produced 550 individuals of P. elaeisis, but rearing this host is difficult in the laboratory (Pereira et al. 2009).
Our study verified that a wild strain of P. elaeisis was more successful at parasitizing pupae of C. anthonilis than those of A. gemmatalis and T. molitor in the laboratory. This is the first report of parasitism by P. elaeisis of C. anthonilis pupae in the laboratory and provides background information for the laboratory rearing of P. elaeisis as a means of biological control of C. anthonilis and other pests.
We thank Dr. Antônio Lélis Pinheiro of the Forest Department of Federal University of Viçosa, Viçosa, Minas Gerais State, Brazil for identifying Piptadenia gonoacantha. “Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)”, “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)”, and “Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)” provided financial support. Dr. Mônica Ruediger de Britto Velho and Asia Science Editing of Republic of Ireland made English corrections and edited this manuscript.