INTRODUCTION Where flight is the main dispersal mode, variation in dispersal ability and its morphological equivalent (wing polymorphism) is widespread and found in numerous insect species (Harrison, 1980; Roff, 1986; Zera & Denno, 1997; Zera, 2009; Simpson et al., 2011) and has ecological and evolutionary consequences (Roff, 1994; Schwander & Leimar, 2011). While flight can be used to colonize new habitats (Denno et al., 1996; Langellotto et al., 2000; Langellotto & Denno, 2001) energy is required to develop and maintain the flight-apparatus. Energy costs might be limited by physiological constraints (Harshman & Zera, 2007; Zera, 2009). Flying individuals have higher metabolic rates even at rest (Reinhold, 1999; Chown et al., 2007) and store considerable amounts of energy for fuelling flight (Zera, 2005, 2009; Zera & Zhao, 2006). Interestingly, the majority of Orthoptera (grasshoppers, crickets and bushcrickets) in Central Europe are wing- dimorphic or polymorphic (Harz, 1969, 1975; Ingrisch & Köhler, 1998). It is suggested that the high level of wing polymorphism is a result of repeated cycles of extensive glaciation in Central Europe during the last 2 million years (Hewitt, 2004; Schmitt, 2007). Recolonization from Asian and Mediterranean refuges may have favoured spe- cies with high colonization capacities, as proposed for wing-dimorphic carabid beetles (Aukema, 1995). In the pygmy grasshoppers (Tetrigidae), which are small, ground dwelling orthopterans that form an ancient clade within the short-horned suborder Caelifera (Flook & Rowell, 1997), there is a similar pattern. In this group, the forewings are reduced to a 1–3 mm long tegmentulum (Devriese, 1996), while the pronotum is prolonged and covers the abdomen and hind wings. The West Palaearctic species vary in their mixture of hindwing- polymorphism, with most species being predominantly LW or SW (Devriese, 1996; Lehmann & Landeck, 2007). We studied populations of Tetrix subulata (Linnaeus, 1758), because in this species two wing morphs occur within the same population (Devriese, 1996; Lock et al., 2006; Berggren et al., 2012). In the SW morph the pro- notum reaches the knees of the hind femurs and the folded hind wings the tip of the pronotum. Individuals described as long-winged, develop hind wings and pro- nota that overhang the knees by several millimetres. However, previous studies have classified individuals visually and only provide measurements of the extended pronotum (Lock et al., 2006; Berggren et al., 2012). In order test for the existence of distinct wing morphs we measured wing size in this study. Observations indicate that the occurrence of the SW morph in T. subulata is associated with poor habitats, such as those at high altitudes (Fontana et al., 2002; Meitzner, unpubl. data) or high latitudes (Rehn & Grant, 1955; Helfer, 1987). Such marginal habitats restrict life cycles, which poses the question is the expression of SW a developmental reaction of less fit individuals (King & Roff, 2010). If this is the case then the expectation is that SW individuals will be smaller than LW individuals. Eur. J. Entomol. 110(3): 535–540, 2013 http://www.eje.cz/pdfs/110/3/535 ISSN 1210-5759 (print), 1802-8829 (online) Morphological variation and sex-biased frequency of wing dimorphism in the pygmy grasshopper Tetrix subulata (Orthoptera: Tetrigidae) ANJA STEENMAN 1 , ARNE W. LEHMANN 2 and GERLIND U.C. LEHMANN 1 * 1 Humboldt-Universität zu Berlin, Department of Biology, Behavioural Physiology, Invalidenstrasse 43, 10115 Berlin, Germany, e-mails: anjasteenman@yahoo.de; gerlind.lehmann@t-online.de 2 Friedensallee 37, 14532 Stahnsdorf, Germany, e-mail: arne.w.lehmann@t-online.de Key words. Orthoptera, Caelifera, Tetrigidae, Tetrix subulata, pygmy grasshopper, polymorphism, polyphenism, wing-dimorphism, sex-biased frequency Abstract. Dimorphism in wing length is well known in many insect species. It is generally believed that a trade-off between dis- persal and reproduction exists, with the long-winged (LW) morph being a better disperser due to its superior flight capability. The short-winged (SW) morph is less mobile and it is hypothesised that females of this morph invest more of their energy reserves in producing offspring. We determined the variation in body and wing size in the pygmy grasshopper Tetrix subulata (Orthoptera: Tetrigidae). The results of the morphological study support the occurrence of two clearly distinct wing morphs in both sexes. SW individuals, especially males, were smaller and in accord with proposed developmental instability showed greater variability in body size than LW individuals. Using data for 700 wild-caught individuals from 10 populations, we demonstrate a variable frequency in the percentage of LW individuals, ranging from all-LW to all-SW populations, even if the LW morph is by far the most common morph in an area. The male-biased percentage of LW individuals recorded in intermediate populations supports a difference in the dispersal reproduction trade-off between the sexes. 535 * Corresponding author.