Altitudinal Record of Dendroctonus approximatus Dietz (Coleoptera: Curculionidae) in Veracruz, Mexico

Among bark beetles, the genus Dendroctonus Erichson causes the most damage to trees in forests around the world (Six and Bracewell 2015), attacking trees of the genera Pinus L., Picea A. Dietr., Pseudotsuga Carrière, and Larix (Mill.) (all Pinaceae) (Wood 1963; Six and Bracewell 2015). The group comprises 20 species (ArmendárizToledano et al. 2015), of which 13 are found in the forests of Mexico. In Mexico, 40.5% of pest control reports are attributed to damage by Dendroctonus species (Pérez-Camacho et al. 2013). Species in this genus have been classified into two groups according to the order of colonization of the host, with six species (D. mexicanus Hopkins, D. frontalis Zimmermann, D. adjunctus Blandford, D. rhizophagus Thomas and Bright (Salinas-Moreno et al. 2010), D. pseudotsugae Hopkins, and D. ponderosae Hopkins) considered as primary pests and the remaining seven as secondary pests, including D. approximatus Dietz (Ruiz et al. 2009; Salinas-Moreno et al. 2010; Vı́ctor and Zúniga 2016). Dendroctonus approximatus attacks 17 species of Pinus, of which the following species are known to occur in Veracruz: P. ayacahuite C. Ehrenb. ex Schltdl., P. hartwegii Lindl., P. montezumae Lamb., P. patula Schltdl. and Cham., P. pseudostrobus Lindl., and P. teocote Schltdl. and Cham. (Salinas-Moreno et al. 2010), practically all of which are economically important species in Mexico. Dendroctonus approximatus usually has one generation per year but can have two generations in years with warmer conditions. The species’ pheromone system is unknown (Six and Bracewell 2015). This report offers the first geo-referenced data on the altitudinal distribution of D. approximatus in the northwestern region of the volcano Cofre de Perote, Veracruz, Mexico. The specimens were collected by means of eight-cone Lindgren traps baited with generalist bait composed of frontalin, alphaand beta-pinene, and endo-brevicomine (Sistema Injecthor De Mexico) from June 2014 to July 2016 in coniferous ecosystems of the communities of El Conejo and Los Pescados (Perote), El Rosario (Xico), and El Zapotal (Acajete) in Veracruz (Table 1). Four traps (three baited and one unbaited) were placed at intervals of 100 m per site. The sites occurred at altitude intervals of 250 m from 2,000 to 3,500 m elevation (Table 1). Beetles caught in traps were collected and transferred to 70% ethyl alcohol every 15 days. Specimens were identified to genus using Wood (1982), and species identification was made by Thomas Atkinson (University of Texas, Austin, TX). Genitalia of collected insects were compared to those of D. approximatus specimens from the Entomological Collection of the Institute of Plant Health of the Colegio de Postgraduados (CEAM) in Texcoco, Mexico, following Vı́ctor and Zúniga (2016). Genitalia were dissected by separating the abdomen from the rest of the body and immersing it in 10% potassium hydroxide at 80° C for 20 minutes to macerate the tissue. Once extracted, the genitalia were immersed in 70%