Fig. 7. Ligature experiments link eclosion hormone with the bursicon pathway and separate wing expansion from tanning. (A) Pharate adults were prepared by dissecting away the puparial case and pupal cuticle surrounding the neck region. These flies were staged using morphological markers (Kimura and Truman, 1990) and neck-ligatured. Following ligature, treated flies were maintained in a humid chamber and observed at intervals for up to 5 h. Ligature of wild-type (wt) flies prior to eclosion induces premature tanning and wing expansion behavior upon eclosion. In EH cell knockouts, tanning and wing expansion are eliminated. Flies lacking rk function (rk⁴) did not melanize but did expand their wings. Ligature-induced wing expansion is accompanied by tonic contraction of the lateral abdominal muscles in both wild-type and (B) rk⁴ mutants.

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