Anim. Behav., 1992,44, 823-832 The quantitative genetics of sound production in Gryllusfirmus KAREN LYNN WEBB & DEREK A. ROFF Department of Biology, McGUl University, Montreal, Quebec, H3A 1B1 Canada (Received 29 August 1991; initial acceptance 11 November 1991; final acceptance 25 January 1992; MS. number: A6144) Abstract. The species-specific calling songs of male crickets are used by females for species recognition and mate choice. Heritability of variation of morphological structures involved in song production, components of the calling song, and body size were estimated for the cricket Gryllusfirmus. The herita- bilities of morphological structures range from 0'42 to 0.73, while those of the song components range from 0.10 to 0-35. Comparison between sire and dam components suggests that there may be non-additive and/or maternal effects. As a result of the low correlation between body size and song components, it is unlikely that female G.firmus use the calling song to assess male body size or wing morph (micropterous or macropterous). In Orthoptera, male song is a major component of the mate recognition system (Regen 1913; Walker 1957; Popov & Shuvalov 1977; Pollack & Hoy 1981; Weber et al. 1981; Pollack 1982; Thorson et al. 1982; Stout et al. 1983; Doherty 1985a, b). Song may be used to convey information not only about the location of the caller but also about the caller's physical characteristics, such as size: for example, Simmons (1988b) found a significant increase in the pulse-repetition rate and a decrease in chirp duration with increasing male size for the cricket Gryllus bimaculatus. That these song components can be assessed by the female cricket is evidenced by the observation that females preferred the calls of large males in playback experiments (Simmons 1988b). Components of calling song found to be import- ant in many species of crickets for species recog- nition and female phonotaxis are number of pulses per chirp, pulse length, pulse repetition rate within chirps (l/pulse period), chirp length, chirp rep- etition rate (1/chirp period) and most intense fre- quency component or carrier frequency (Doherty & Hoy 1985). Females appear to evaluate several of these components (reviewed by Doherty & Hoy 1985); if females differ in their evaluation of song attractiveness, and song components are heritable, variations in song may persist. Hedrick (1988) found that calling-bout length, in the cricket Gryllus integer, was significantly heri- table (h2=0.75, P<0-0005), and virgin females were preferentially attracted to long calling-bout lengths (Hedrick 1986). However, little is known, overall, about genetic variation in the components of the calling song within Orthopteran species, and their effects on female mate choice (Crankshaw 1979; Hedrick 1986, 1988; Simmons 1987, 1988b). Butlin & Hewitt (1986) examined the heritability of morphology and song characteristics of the grass- hopper Chorthippus brunneus. Heritabilities for morphological features were generally higher than song components (h2= -0.21-0.28 for song components, and h 2 = 0-16-0.89 for morphological features). However, none of the heritability esti- mates for song components were significant, though, this may be a result of small sample sizes (90<N<95, where N= individuals per sample) with the consequently high standard errors (Butlin & Hewitt 1986). The sand cricket, Gryllus firmus, is a large ground-dwelling cricket native to the south-eastern United States (Alexander 1968), and is well suited as a subject for the analysis of heritability of both morphological and song components. It is easy to rear in large numbers and its generation time is relatively short (approximately 60 days from egg to adult at 28~ Males of G.firmus produce three types of calls: a calling song that attracts females from a distance, a courtship song that is used by the male when in very close proximity to the female, and an aggressive song used primarily in male-male interactions. The courtship song may be an import- ant secondary mechanism by which species recog- nition may occur, and is required by females 0003-3472/92/110823 + 10 $08.00/0 9 1992The Association for the Study of Animal Behaviour 823