Sybra alternans (Wiedemann, 1823)

Mondaca, José, Ramírez, Francisco & Rothmann, Sergio, 2016, Sybra alternans (Wiedemann) (Lamiinae: Apomecynini): an Asian cerambycid established on Easter Island, Chile, Insecta Mundi 2016 (503), pp. 1-6 : 2-3

Sybra alternans (Wiedemann, 1823)

( Fig. 1 )

Material Examined. Chile, Valparaíso Region: Easter Island [Rapa Nui], UV light trap, VI-2011, III- 2014, 22-XII-2014, col. C. Valdés (3 females). Valparaíso Region, Rapa Nui, UV light trap, 1-X-2014, col. S. Ríos (1 female). Valparaíso Region, Rapa Nui, UV light trap, 23-III-2015, col. S. Ríos (2 females). Chile, Valparaíso Region, Easter Island, sector Hanga Kio’e, beating Erythrina sp. , 20-IV-2016, leg. F. Ramírez (1 female).

Host Plants. Sybra alternans is a polyphagous species that infests numerous host plants. It has been detected attacking some fruit trees and crops such as Ficus carica L. ( Moraceae , “fig tree”), Ananas comosus (L.) Merr. ( Bromeliaceae , “pineapple”), Musa paradisiaca L. ( Musaceae , “banana”), Phaseolus vulgaris L. ( Fabaceae , “bean”), Ocimum basilicum L. ( Lamiaceae , “basil”), Gossypium hirsutum L. ( Malvaceae , “cotton”), Saccharum officinarum L. ( Poaceae , “sugar cane”), and some ornamental plants typical of the South Pacific island. For a full list of host and respective citations, see Chen et al. (2001). In Florida, it was collected from dead limbs of Ficus aurea Nutt. ( Moraceae , “golden fig”) ( Thomas 2000), while on Easter Island an adult was captured by shaking the dry branches of Erythrina sp. trees ( Fabaceae , “ceibo”).

Distribution. Sybra alternans is an Asian species distributed in Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, Taiwan, Indonesia, Mariana Islands, Caroline Islands, Marshall Islands, and the Philippines ( Rondon and Breuning 1970; Roguet 2016). It was introduced in the early twentieth century to Hawaii (see details in Chen et al. 2001) and more recently to Florida in the United States of America ( Thomas 2000). It may have arrived in Florida via military flights from the Hawaiian Oahu military bases to those at Homestead, Florida ( Samuelson and Howarth 2013). In Chile, S. alternans is known to occur only on to Easter Island, Valparaíso Region (new record) ( Fig. 2 ).

Biology. The life cycle of S. alternans has been described briefly by Swezey (1950), who mentions that the life cycle can be completed in about four months. Adults are nocturnally active and seem to oviposit preferentially on host plants that are thoroughly dried. This cerambycid feeds on the inner fermenting and decaying bark and the outer sapwood. The larvae bore into the wood to pupate for their final transformation to adults.

Remarks. Repeated collections of S. alternans during six years in two different parts of Easter Island ( Chile) provide strong evidence that a population of this cerambycid has successfully established on the island. Because the collection sites of S. alternans are located near the airport of Mataveri (see Fig. 2 ), it is likely that this species reached Easter Island via international commercial flights. Samuelson and Howarth (2013) proposed a similar hypothesis (but through military flights) to try to explain the introduction of this species from Hawaii to Florida.

Figures

Figure 1. Female specimen of Sybra alternans (Wiedemann) collected on Easter Island (Chile), dorsal habitus. Scale bar = 2 mm.

Figure 2. Collection sites for Sybra alternans on Easter Island, Chile (black circles). Rapa Nui National Park is indicated in light grey.