Aerial performance of stalk-eyed flies that differ in eye span

Area of Science:

• * Evolutionary biology
• * Animal morphology
• * Biomechanics

Background:

• * Stalk-eyed flies possess laterally displaced eyes on elongated peduncles.
• * Elongated eye spans may incur flight costs (energetic, aerodynamic, load) or necessitate compensatory morphology.

Purpose of the Study:

• * To test the hypothesis that eye span elongation correlates with increased head mass in stalk-eyed flies.
• * To investigate the relationship between eye span, body dimensions, and flight performance in two species.

Main Methods:

• * Measurement of body mass and dimensions in two species: sexually dimorphic Cyrtodiopsis whitei and monomorphic Cyrtodiopsis quinqueguttata.
• * Comparison of head mass, body mass, and morphometric traits between species and sexes.
• * Three-dimensional flight path tracking to analyze aerial performance metrics.

Main Results:

• * Despite longer eye spans in C. whitei, head mass did not differ significantly between species after controlling for body mass.
• * C. whitei males exhibited distinct morphometrics (longer wings, heavier thorax, lighter abdomen) relative to body mass.
• * Long-eyed C. whitei males demonstrated reduced aerial performance, flying at shallower ascent angles and with reduced vertical velocity, though path velocity and horizontal velocity were similar.

Conclusions:

• * Eye span elongation in stalk-eyed flies is not directly correlated with increased head mass.
• * Reduced flight performance in males of C. whitei is likely due to aerodynamic factors like increased drag or wake effects, rather than increased mass.
• * Potential constraints on visual processing may also contribute to altered flight dynamics.