Recent studies of the family Meloidae (Coleoptera) provided a framework for the study of the Mexican fauna. The identification keys of genera for the American continent (Pinto & Bologna, 1999), phylogenetic hypotheses for the group (Bologna & Pinto, 2001; Bologna et al., 2008), and the Catalogue of Mexican Meloidae (García-París et al., 2007), fostered the study of this family in Mexico. As a consequence, various works dealing with Mexican fauna have appeared recently, including taxonomic revisions (Pinto, 2009; García-París & Ruiz, 2013), addition of new species for the Mexican fauna (García-París et al., 2008, 2009; García-París & Ruiz, 2009), revision of local faunas (García-París et al., 2009), description of new species (Pinto, 2010; García-París & Ruiz, 2013), resolution of taxonomic problems (García-París et al., 2013a), and rediscovery of species unseen for decades (García-París et al., 2013b).

Despite these works, the Mexican fauna of Meloidae is still far from adequately known. Taxonomic revisions of most groups are still lacking, geographic distributions are not properly known, and large areas of the country are still insufficiently explored. An example of this situation is represented by the difference of knowledge along the Mexico-US border. A large number of species that could be present in Mexican territory are only known north of the border (García-París et al., 2007). This artificial border crosses the territory, in an almost straight line, splitting typical habitat favourable for Meloid beetles at both sides (as the Sonoran and Chihuahuan deserts in the west) (Cohen & Pinto, 1977). This deficit of records on the Mexican side is particularly relevant for the tribes Epicautini, Lyttini and Eupomphini (Selander, 1960; Pinto, 1979, 1984, 1991).

The tribe Eupomphini includes 26 species restricted to arid and semiarid zones of south-western North America, in Mexico and USA (Pinto, 1984). Eighteen of these species have been reported from Mexico (4 endemics), but several other species are only known from the US side of the Mexico-USA border (García-París et al., 2007). Three of these species are included in the genus Eupompha LeConte 1858. Eupompha, is the largest genus of the tribe, with 12 species distributed over much of arid and semiarid southwestern North America, from Guerrero to Nevada (Pinto, 1979, 1983, 1984). Eupompha terminalis Selander, 1957, and E. sulcifrons (Champion, 1892) are endemic to western Mexico (Michoacán and Guerrero); E. vizcaina and E. decolorata are endemic to the peninsula of Baja California (Mexico); E. fissiceps LeConte, 1858, E. elegans (LeConte, 1851), E. wenzeli (Skinner, 1904), and E. viridis (Horn, 1883), occur both in Mexico and USA; E. edmunsi Selander, 1953, is endemic to Utah and northern Arizona (USA); and E. imperialis (Wellman, 1912), E. schwarzi (Wellman, 1909), and E. histrionica (Horn, 1891) are so far restricted to south-western USA (Pinto, 1979, 1983; García-París et al., 2007).

Eupompha imperialis is a small and delicate species included in the E. elegans species group (sensu Pinto, 1979). The species was described from “Meloland” in the Imperial Valley of California (Wellman, 1912). Since then, it has been located in arid regions of the Sonoran Desert in south-eastern California and south-western Arizona, usually found feeding on flowers of Tiquilia palmeri (A. Gray) A. Richardson (Boraginaceae) and Sphaeralcea (Malvaceae) (Pinto, 1979). It is characterized by a typical color pattern: rufous with pale, bone-coloured, elytra (Figs. 3 & 4) (Wellman, 1912; Pinto, 1979), and by the presence of a tuft of cinereous setae along the midline of the metasternum in males. Other features of males of E. imperialis are: presence of a shallow median sulcus on the head, running from the base of clypeus to the vertex (Fig. 3), and swollen tarsal segments, particularly the basal one (Pinto, 1979). The courtship (Pinto, 1977) and the larval morphology (Pinto, 1975) of E. imperialis is similar to that of E. elegans and E. decolorata.

In recent years, we visited the north-western regions of Mexico to study the meloid fauna of the area. As a result, we discovered some populations of E. imperialis, which represent the first records of the species in the country. Here we report these new records, make comments on the habitat of E. imperialis and show the first photographs of live specimens of this unconspicuous species of Eupompha.

Specimens of E. imperialis were observed at the following localities in north-western Mexico: Baja California: 12 km WSW of Mexicali, 9 m altitude, 32°35'24''N-115°38'56''W: 23-IV-2008, 11 specimens (C. Settanni & M. García-París) (Fig. 1); 2 km NE Ejido Mérida, about 8 km SW Los Algodones (Vicente Guerrero), 28 m altitude, 32°40'07''N-114°53'20''W: 22-IV-2008, 15 specimens (C. Settanni & M. García-París). Sonora: 3 km E San Luis del Río Colorado, 49 m altitude, 32°26'29''N-114°38'42''W, 22-IV-2008, 2 specimens (C. Settanni & M. García-París) (Fig. 2).

Populations of E. imperialis in Mexico were located in large patches of sandy soil with sparse vegetation, similar to the habitat described for California (Pinto, 1979) (Figs. 1 & 2). All three Mexican localities were detected close to large denuded sand areas (Algodones and La Salada dunes in Baja California, and El Altar dunes in Sonora), near the Mexico-US border (Fig. 2). Adult specimens of E. imperialis were always located in the interior parts of flowering Tiquilia palmeri (Fig. 3), non-visible from above. The specimens run outside the plant when disturbed (Fig. 4). Courtship (Fig. 3) was observed after some period of reclusion in plastic boxes, and it did not differ from the pattern described by Pinto (1977). Population density was relatively high in Baja California, but low in Sonora. The specimens observed fit with the description provided by Pinto (1977) showing a large variation in the coloration of ventral sternites, from pale orange to almost dark brown (Fig. 3).

Most species of Eupompha are poorly represented in collections (Pinto, 1979). This is the case for the Mexican species, represented by only a few specimens at the Colección Nacional de Insectos (Instituto de Biología, UNAM). Pinto (1979) suggested that this paucity of specimens in collections is due to the restricted geographic distribution range and low population densities of most species, and perhaps due to the failure of adults to emerge on all years. We also believe that the scarcity of data on the Mexican side of the Sonoran and Chihuahuan deserts is a consequence of inadequate sampling. Records of Eupomphini in Mexico are scattered and poor, even for showy and colourful species (as those of Tegrodera and Megetra) (García-París et al., 2007).

With the inclusion of E. imperialis, the representation of the tribe Eupomphini in Mexico reaches 19 species. However, in our oppinion, adequate collection in Mexico adjacent to the northern frontier would substantially increase the number of species of Meloidae for this country, particularly of tribes Epicautini and Lyttini, by adding species that are currently known as inhabitants of the northern side of the Mexico-US border, as was the case of E. imperialis and Lytta mirifica Werner, 1951 (García-París & Ruiz, 2009).