There was an error published in J. Exp. Biol. 219, 977-987.
In the set of ordinary differential equations derived from Eqn 8 and in Eqns 10 and 12, the second minus sign on the right-hand side of the equations should have been a plus sign; in addition, in the derived equations and in Eqn 10, g was missing. The correct equations are shown below.
The authors apologise for any confusion this may have caused.
© 2016. Published by The Company of Biologists Ltd