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Fig. 11. Model for achieving take-off performance. (A) We hypothesize that a minimum
of four independent pathways are required to coordinate take-off behavior: one
coordinating wing opening on either side of the body and two coordinating
different types of leg extension. In our model, take-off performance is
determined by both the latency between activation of wing and leg pathways
and the choice of leg pathway. In our diagram 
1
represents the delay due to sensory and/or central processing before one or
both wing pathways are activated, and 2 represents the delay
before activation of one of the leg pathways. The difference between these two
delay times is the observed wing–leg interval, . We propose that
which leg pathway is activated for a given take-off determines the speed of
that take-off. Alt., alternate. (B) The latency between wing and leg
pathway activation determines take-off steadiness. This model is supported by
our data: the graph shows the time between first wing motion and first
leg motion plotted against the resulting take-off steadiness S for
each fly observed (N=43). Upward-pointing triangles represent
voluntary take-offs, while upside-down triangles mark escape responses. The
fill color of the upside-down triangles (escapes) indicates the conditions of
the wings during take-off, as defined in
Fig. 10: black,
**Esc. (N=5); white, *Esc. (N=5);
gray, Esc. (N=17). The green line is a best-fit linear regression to
the data. The line has a positive slope, indicating a direct correlation
between and steadiness. (C) Summary of how coordination of the
hypothesized pathways leads to the observed differences in take-off
performance.
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