The proboscis of Vanessa cardui (Nymphalidae) contains two basal galeal mus
cles and two different series of numerous oblique muscles. Both muscle seri
es extend from the proximal region up to the tip-region; the individual mus
cles of each series run a constant course throughout the proboscis. In cont
rast to other butterflies, the knee bend region does not have additional ty
pes of muscles. The analysis of shock-frozen proboscises reveals that the d
orsal wall is arched outwardly in the uncoiled, feeding position whereas in
the coiled, resting position the dorsal proboscis wall is flat or concave.
This results in a significantly greater cross-sectional area due to the si
gnificantly greater dorso-ventral diameter in uncoiled proboscises. After f
reezing the proboscis in its distal region, it can still be uncoiled, howev
er, it cannot be fully recoiled. These morphometric and experimental result
s indicate that the oblique proboscis muscles are responsible for recoiling
the proboscis to the resting position.