Fig. 3. A comparison of the properties of muscle fibres (M214) from mature females (>18 days old) treated with precocene or precocene plus juvenile hormone (JH). (A) The length/twitch tension relationship, showing that longitudinal muscles from precocene-treated females were not able to tolerate a length exceeding 4.5 mm without breaking (arrow). At this length, approximately 20 % of maximum tension was generated. In contrast, muscles from females treated with precocene plus JH tolerated extensions up to 8 mm and above and still generated more than 30 % of maximum tension. f_l/f_max, muscle tension at a particular length normalized to maximum tension. (B) The passive length/tension relationship revealed pronounced differences. Passive tension increased steeply in muscles from precocene-treated females, whereas muscles from females treated with precocene plus JH generally exerted a lower tension that increased more slowly. (C) The maximum tension generated by the two groups differed significantly (P<0.05). The tension generated by muscles from precocene-treated animals was approximately one-third of the tension generated by muscles from animals treated with precocene plus JH. TW, twitch. An asterisk indicates statistical significance (Mann–Whitney rank sum test, P<0.05). Values are means ± S.E.M. (D) A comparison of tetanus fusion frequencies revealed no consistent differences comparable with those in Fig. 2D. (E) To confirm that the corpora allata (CA) from animals injected with precocene plus JH were indeed affected by precocene, the CA from these females were compared with those of untreated females (Control). The diameter of the CA from treated females was approximately 30 % of that of control females.