Nemocephalus monilis (Fabricius, 1787) (Coleoptera: Curculionoidea: Brentidae), an Apparently Recent Arrival and Effective Colonizer of the Oceanic Island of Saba, Dutch Caribbean

Abstract

In 2010, the brentid weevilNemocephalus monilis (Fabricius, 1787) was discovered in large numbers at Round Hill, The Bottom, and subsequently at other localities on Saba Island in the Dutch Caribbean. Earlier intensive collecting of beetles during 2006–2007 on the island had failed to record this species. The available data suggest that Saba may have been effectively colonized by N. monilis during the late 2000s. The tiny Caribbean island of Saba, only 13 km in area, is the northernmost island in the inner arc of the Leeward Islands group of the Lesser Antilles, situated at approximately 17.63°N, 63.24°W (Fig. 1). Since the dissolution of the Netherlands Antilles in October 2010, Saba became the smallest special municipality of the Netherlands. The island is known to locals as the Unspoiled Queen on account of its relatively pristine marine and terrestrial environments, compared with many other Caribbean islands. Physically, the island consists mainly of the top of a dormant but potentially active volcano, known as Mount Scenery, which rises to an elevation of 887 m. Most of the upper reaches of the mountain are cloaked chiefly in secondary rainforest, forming the hygrophilic or humid forest zone. Lower down the mountainside and on the other hills surrounding Mt. Scenery, there is a mesophilic zone consisting of Leeward Islands dry forest and naturalized fruit trees such as avocado, mango, and grapefruit. Below this zone, and extending to the rocky shores of the island, is a xerophilic zone consisting of Leeward Islands xeric scrub and grassland, which is at its most extensive on the eastern and southern sides of the island (Rojer 1997). The marine fishes, reptiles, birds, amphibians, and terrestrial plants of Saba are reasonably well known (Rojer 1997), but in general, other groups remain little known. However, recent accounts of the spider (Slowik and Sikes 2011) and myriapod (Shelley and Sikes, 2012) fauna of Saba are published. There is also a list of Saban butterflies available (Rojer 1997), but it is incomplete (MPTG, personal observations). Most other orders of insects, including the Coleoptera, on Saba are unknown, incompletely known, or unpublished. Peck (2009) estimated the number of beetle species for each island of the Lesser Antilles based on surface area and the well-documented coleopterous fauna of Montserrat (Ivie et al. 2008) as a reference point. The number of beetle species for Saba was estimated to be in the order of 440, but hitherto records of only some 55 species (belonging to 23 families) have been published for the island, including, most recently, three species of Dynastinae (Scarabaeidae) (Peck 2009, 2011, 2015; Maier and Ivie 2013; Gillett et al. 2014; Gillett and Gillett 2015). The present communication adds a further species as well as a new family to the beetle fauna of Saba, together with evidence that these represent a very recent colonization of the island. In January 2006, MPTGmoved to Saba and lived on the island until December 2007, during which