A divided visual field

Date:
March 23, 2021
Source:
University of Wu"rzburg
Summary:
How do hawkmoths use visual patterns in different parts of their
visual field? While researching this question, a research team
experienced a surprise.



FULL STORY ========================================================================== Hummingbird hawkmoths are small insects that hover in the air like
hummingbirds when drinking nectar from flowers. Dr. Anna Sto"ckl from
the Biocentre of the Julius-Maximilians-Universita"t (JMU) Wu"rzburg
in Bavaria, Germany, is studying the visual performance of these
insects. Dr. Sto"ckl and her doctoral student Ronja Bigge now present
their latest findings in the journal Current Biology.


==========================================================================
"To control their flight, hummingbird hawkmoths rely on optic flow in
the lower half of their visual field," Ronja Bigge explains. Optic flow
is the relative motion that the surrounding image casts on the animals'
retinas when they fly.

We experience this phenomenon ourselves when travelling by train -- the landscape passing by the train windows allows us to estimate our speed,
for example.

For hawkmoths, the optic flow also provides information about their
own movement. It helps them to control the straightness and speed of
their flight.

The JMU researchers have now shown with outdoor measurements that the
optic flow components parallel to the direction of flight are always
strongest below the hawkmoths' body. This is where the insects see
meadows, gardens and streets that provide a varied texture. For flight
control, what happens in the lower visual field is therefore the most
reliable parameter.

Previously unknown behaviour discovered "Surprisingly, we were able
to show that the hawkmoths displayed a completely different and novel
behaviour when we presented them with visual textures in the upper half
of their visual field," says Anna Sto"ckl.

The animals then oriented themselves along prominent contours in the
patterns.

Thus, they did not use the visual information for flight control, but
for orientation -- although the visual patterns were exactly the same
as the ones that were previously presented in the lower half of their
visual field.

"Our optical measurements in natural habitats showed a comparable
relationship: high-contrast structures that can be used for orientation
occur primarily in the upper half of the visual field," says the JMU researcher. These are, for example, the silhouettes of treetops or bushes
that form a strong contrast with the sky.

Visual field is divided in two The conclusion of the Wu"rzburg biologists:
"The flight control system and the orientation system of the hummingbird hawkmoth divide the visual field among themselves and focus on the
respective area that provides the most reliable information in their
natural habitats." In other words, it is not only important what the
animals see, but also where they see it.

========================================================================== Story Source: Materials provided by University_of_Wu"rzburg. Original
written by Robert Emmerich. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Ronja Bigge, Maximilian Pfefferle, Keram Pfeiffer, Anna
Sto"ckl. Natural
image statistics in the dorsal and ventral visual field match a
switch in flight behaviour of a hawkmoth. Current Biology, 2021;
31 (6): R280 DOI: 10.1016/j.cub.2021.02.022 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/03/210323131208.htm

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