Abstract:  The sand field cricket, Gryllus firmus, is a wing-polymorphic insect, a model insect for studying fitness of reproduction and dispersal within species. In this study, we qualitatively and quantitatively analyzed titers of juvenile hormone (JH) and fatty acids in flight muscles between the long wing ［LW(f), flight-capable］ and the short wing (SW, flightless) females by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results showed that JH titers at 4 h before flight on day 5 and 7 of LW(f) morph exhibited a daily rhythm with about 3.4- and 2.7-fold increases, respectively (P<0.05) compared with those in SW morph, that is, from 386.52±68.40 ng/g to 1 327.53±277.98 ng/g on day 5 and from 630.36±37.26 ng/g to 1 685.77±143.95 ng/g on day 7, respectively. By contrast, there was no significant daily variation of JH titers on day 5 and 7 of SW morph, and day 1 of both morphs. Further, the 14-methyl-pentadecanoic acid, a C16 fatty acid, was also found to exhibit a daily rhythm on the day 5 and 7 of the LW(f) morph with temporal consistency with the JH peak, which did not occur in the flightless morph. The experiments also prove that the daily rhythm of JH titers is not due to the variation in flight muscle mass or the ratio of flight muscle mass. These results help us to understand the relationship between JH titer and flight behavior.

Key words: Gryllus firmus, diurnal rhythm, wing dimorphism, juvenile hormone (JH), fatty acid