Invasion of Two Widely Separated Areas of Mexico byForficula auricularia(Dermaptera: Forficulidae)

Abstract

The European earwig, Forficula auricularia L. 1758 (Dermaptera: Forficulidae), is a household pest and an invasive species with cosmopolitan distribution. It is native to Europe, Western Asia and probably North Africa, although it has spread to all continents except Antarctica (Crumb et al. 1941; Clausen 1978; Shakai 1987). Earwigs are carried from one place to another on clothing or commercial products such as lumber, ornamental shrubs, newspaper bundles and groceries. Euro pean earwigs are nocturnal omnivorous scaven gers and predators, most commonly found in tem perate climates. They prefer moist and warm hab itats, having an optimum mean growth tempera ture of 24 °C, and are most active when the daily temperature has minimal fluctuation (Crumb et al. 1941; Capinera 2001; Jacob 2009). The species has been known to cause significant damage to crops, flowers, and fruit orchards when they occur at high population densities (Vickery & Kevan 1986; Walker 1997; Capinera 2001; Weems & Skelly 2009). Forficula auricularia was recorded a number of times in North America along the 19th century before becoming established on the continent (Vickery & Kevan 1983; Guillet et al. 2000). The first known colony of the species on the Atlantic coast appeared in Newport, Rhode Island in 1911 (Glaser 1914; Guillet et al. 2000), whereas on the Pacific coast, the earwig was present in Seattle al ready in 1907 (Coyne 1928) and in Oregon in 1909 (Guillet et al. 2000). Since then, the species has spread on both coasts of the US (Wirth et al. 1998), as well as to several Canadian provinces. Expansions were initiated by population bursts in harbors, a phenomenon never observed in Eu rope, and the species rapidly became a nuisance, thus causing concern on the part of agricultural authorities, who used different measures to erad icate this pest, including poisoning campaigns. The geographic range of F. auricularia has clearly expanded since, as it has continuously been re ported in different localities farther inland (Crumb et al. 1941; Wirth et al. 1998). Despite this ability to colonize new environments, there were no precise records of F. auricularia in Mex ico and Central America prior to this work (Scud der 1868; De Bormans 1893; Hebard 1917; Clausen 1978; Young 1986; Maes & Haas 2006; Weems & Skelly 2009). During a recent field trip carried out at the La gunas de Zempoala National Park, in the state of Mexico (municipality of Ocuilan; 2824 m absl; 21 VIII-2010), we found a reproductive aggregation of about 20 specimens of F. auricularia, which was grouped under loose bark on a vertical fence pole. This fence separates the surrounding pas tures from one of the tourist stands at Lagunas de Zempoala. Most of the specimens dropped from the pole after being exposed, but 6 were captured and photographed (Fig. 1). No other specimens were found immediately nearby. Furthermore, we observed an explosive irrup tion of F. auricularia on the Mexican island of