DIHYDROPYRROLIZINES FROM THE MALE SCENT-PRODUCING ORGANS OF A DANAID BUTTERFLY, IDEOPSIS-SIMILIS (LEPIDOPTERA, DANAIDAE) AND THE MORPHOLOGY OF ALAR SCENT ORGANS

Males of Ideopsis similis were found to secrete two kinds of dihydropyrrolizine derivatives: hydroxydanaidal from the abdominal hairpencils and danaidone from the hindwings. Although structures similar to alar patches or pockets characteristic of most danaid males are lacking in I. similis, electron microscopic examination revealed the presence of modified scales mainly in cell 1A + 2A of the hindwings. Beneath these modified scales were found peculiar integumental structures recognized as secretory organs, which might play an important role in secretion and/or production of danaidone. The findings suggest that in I. similis, unlike other danaid butterflies, the two dihydropyrrolizines may be independently produced in different organs. The average quantity of hydroxydanaidal secreted by the spring population amounted to 48.3 mu g/male, while that of the autumn population was only 7.3-8.4 mu g/ male. In contrast, the amount of danaidone, with an average of 3.2 (spring) or 2.1 (autumn) mu g/male, showed no noticeable seasonal variation.